# systemd.exec

## NAME



           systemd.exec - Execution environment configuration
    


## SYNOPSIS



           _service_.service, _socket_.socket, _mount_.mount, _swap_.swap
    


## DESCRIPTION



           Unit configuration files for services, sockets, mount points, and
           swap devices share a subset of configuration options which define
           the execution environment of spawned processes.
    
           This man page lists the configuration options shared by these four
           unit types. See systemd.unit(5) for the common options of all unit
           configuration files, and systemd.service(5), systemd.socket(5),
           systemd.swap(5), and systemd.mount(5) for more information on the
           specific unit configuration files. The execution specific
           configuration options are configured in the [Service], [Socket],
           [Mount], or [Swap] sections, depending on the unit type.
    
           In addition, options which control resources through Linux Control
           Groups (cgroups) are listed in systemd.resource-control(5). Those
           options complement options listed here.
    


## IMPLICIT DEPENDENCIES



           A few execution parameters result in additional, automatic
           dependencies to be added:
    
           •   Units with _WorkingDirectory=_ , _RootDirectory=_ , _RootImage=_ ,
               _RuntimeDirectory=_ , _StateDirectory=_ , _CacheDirectory=_ ,
               _LogsDirectory=_ or _ConfigurationDirectory=_ set automatically
               gain dependencies of type _Requires=_ and _After=_ on all mount
               units required to access the specified paths. This is
               equivalent to having them listed explicitly in
               _RequiresMountsFor=_.
    
           •   Units with _PrivateTmp=yes_ automatically gain dependencies of
               type _Wants=_ and _After=_ on all mounts required to access /tmp/
               and /var/tmp/. They will also gain an automatic _After=_
               dependency on systemd-tmpfiles-setup.service(8).
    
           •   Units with _PrivateTmp=disconnected_ automatically gain
               dependencies of type _Wants=_ and _After=_ on the mount required
               to access /var/, unless _DefaultDependencies=no_ and/or
               _RootDirectory=/RootImage=_ are specified.
    
           •   Units whose standard output or error output is connected to
               **journal** or **kmsg**(or their combinations with console output,
               see below) automatically acquire dependencies of type _After=_
               on systemd-journald.socket.
    
           •   Units using _LogNamespace=_ will automatically gain ordering and
               requirement dependencies on the two socket units associated
               with systemd-journald@.service instances.
    


## PATHS



           The following settings may be used to change a service's view of
           the filesystem. Please note that the paths must be absolute and
           must not contain a ".."  path component.
    
           _ExecSearchPath=_
               Takes a colon separated list of absolute paths relative to
               which the executable used by the _Exec*=_ (e.g.  _ExecStart=_ ,
               _ExecStop=_ , etc.) properties can be found.  _ExecSearchPath=_
               overrides _$PATH_ if _$PATH_ is not supplied by the user through
               _Environment=_ , _EnvironmentFile=_ or _PassEnvironment=_. Assigning
               an empty string removes previous assignments and setting
               _ExecSearchPath=_ to a value multiple times will append to the
               previous setting.
    
               Added in version 250.
    
           _WorkingDirectory=_
               Takes a directory path relative to the service's root
               directory specified by _RootDirectory=_ , or the special value
               "~". Sets the working directory for executed processes. If set
               to "~", the home directory of the user specified in _User=_ is
               used. If not set, defaults to the root directory when systemd
               is running as a system instance and the respective user's home
               directory if run as user. If the setting is prefixed with the
               "-" character, a missing working directory is not considered
               fatal. If _RootDirectory=_ /_RootImage=_ is not set, then
               _WorkingDirectory=_ is relative to the root of the system
               running the service manager. Note that setting this parameter
               might result in additional dependencies to be added to the
               unit (see above).
    
           _RootDirectory=_
               Takes a directory path relative to the host's root directory
               (i.e. the root of the system running the service manager).
               Sets the root directory for executed processes, with the
               pivot_root(2) or chroot(2) system call. If this is used, it
               must be ensured that the process binary and all its auxiliary
               files are available in the new root. Note that setting this
               parameter might result in additional dependencies to be added
               to the unit (see above).
    
               The _MountAPIVFS=_ and _PrivateUsers=_ settings are particularly
               useful in conjunction with _RootDirectory=_. For details, see
               below.
    
               If _RootDirectory=_ /_RootImage=_ are used together with
               _NotifyAccess=_ the notification socket is automatically mounted
               from the host into the root environment, to ensure the
               notification interface can work correctly.
    
               Note that services using _RootDirectory=_ /_RootImage=_ will not be
               able to log via the syslog or journal protocols to the host
               logging infrastructure, unless the relevant sockets are
               mounted from the host, specifically:
    
               The host's os-release(5) file will be made available for the
               service (read-only) as /run/host/os-release. It will be
               updated automatically on soft reboot (see:
               systemd-soft-reboot.service(8)), in case the service is
               configured to survive it.
    
               **Example 1. Mounting logging sockets into root environment**
    
                   BindReadOnlyPaths=/dev/log /run/systemd/journal/socket /run/systemd/journal/stdout
    
               In place of the directory path a ".v/" versioned directory may
               be specified, see systemd.v(7) for details.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
           _RootImage=_
               Takes a path to a block device node or regular file as
               argument. This call is similar to _RootDirectory=_ however
               mounts a file system hierarchy from a block device node or
               loopback file instead of a directory. The device node or file
               system image file needs to contain a file system without a
               partition table, or a file system within an MBR/MS-DOS or GPT
               partition table with only a single Linux-compatible partition,
               or a set of file systems within a GPT partition table that
               follows the **Discoverable Partitions Specification******[1].
    
               When _DevicePolicy=_ is set to "closed" or "strict", or set to
               "auto" and _DeviceAllow=_ is set, then this setting adds
               /dev/loop-control with **rw** mode, "block-loop" and
               "block-blkext" with **rwm** mode to _DeviceAllow=_. See
               systemd.resource-control(5) for the details about
               _DevicePolicy=_ or _DeviceAllow=_. Also, see _PrivateDevices=_
               below, as it may change the setting of _DevicePolicy=_.
    
               Units making use of _RootImage=_ automatically gain an _After=_
               dependency on systemd-udevd.service.
    
               The host's os-release(5) file will be made available for the
               service (read-only) as /run/host/os-release. It will be
               updated automatically on soft reboot (see:
               systemd-soft-reboot.service(8)), in case the service is
               configured to survive it.
    
               In place of the image path a ".v/" versioned directory may be
               specified, see systemd.v(7) for details.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 233.
    
           _RootImageOptions=_
               Takes a comma-separated list of mount options that will be
               used on disk images specified by _RootImage=_. Optionally a
               partition name can be prefixed, followed by colon, in case the
               image has multiple partitions, otherwise partition name "root"
               is implied. Options for multiple partitions can be specified
               in a single line with space separators. Assigning an empty
               string removes previous assignments. Duplicated options are
               ignored. For a list of valid mount options, please refer to
               mount(8).
    
               Valid partition names follow the **Discoverable Partitions**
               **Specification******[1]:**root** , **usr** , **home** , **srv** , **esp** , **xbootldr** , **tmp** ,
               **var**.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 247.
    
           _RootEphemeral=_
               Takes a boolean argument. If enabled, executed processes will
               run in an ephemeral copy of the root directory or root image.
               The ephemeral copy is placed in
               /var/lib/systemd/ephemeral-trees/ while the service is active
               and is cleaned up when the service is stopped or restarted. If
               _RootDirectory=_ is used and the root directory is a subvolume,
               the ephemeral copy will be created by making a snapshot of the
               subvolume.
    
               To make sure making ephemeral copies can be made efficiently,
               the root directory or root image should be located on the same
               filesystem as /var/lib/systemd/ephemeral-trees/. When using
               _RootEphemeral=_ with root directories, **btrfs**(5) should be used
               as the filesystem and the root directory should ideally be a
               subvolume which **systemd** can snapshot to make the ephemeral
               copy. For root images, a filesystem with support for reflinks
               should be used to ensure an efficient ephemeral copy.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 254.
    
           _RootHash=_
               Takes a data integrity (dm-verity) root hash specified in
               hexadecimal, or the path to a file containing a root hash in
               ASCII hexadecimal format. This option enables data integrity
               checks using dm-verity, if the used image contains the
               appropriate integrity data (see above) or if _RootVerity=_ is
               used. The specified hash must match the root hash of integrity
               data, and is usually at least 256 bits (and hence 64 formatted
               hexadecimal characters) long (in case of SHA256 for example).
               If this option is not specified, but the image file carries
               the "user.verity.roothash" extended file attribute (see
               xattr(7)), then the root hash is read from it, also as
               formatted hexadecimal characters. If the extended file
               attribute is not found (or is not supported by the underlying
               file system), but a file with the .roothash suffix is found
               next to the image file, bearing otherwise the same name
               (except if the image has the .raw suffix, in which case the
               root hash file must not have it in its name), the root hash is
               read from it and automatically used, also as formatted
               hexadecimal characters.
    
               If the disk image contains a separate /usr/ partition it may
               also be Verity protected, in which case the root hash may
               configured via an extended attribute "user.verity.usrhash" or
               a .usrhash file adjacent to the disk image. There's currently
               no option to configure the root hash for the /usr/ file system
               via the unit file directly.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 246.
    
           _RootHashSignature=_
               Takes a PKCS7 signature of the _RootHash=_ option as a path to a
               DER-encoded signature file, or as an ASCII base64 string
               encoding of a DER-encoded signature prefixed by "base64:". The
               dm-verity volume will only be opened if the signature of the
               root hash is valid and signed by a public key present in the
               kernel keyring. If this option is not specified, but a file
               with the .roothash.p7s suffix is found next to the image file,
               bearing otherwise the same name (except if the image has the
               .raw suffix, in which case the signature file must not have it
               in its name), the signature is read from it and automatically
               used.
    
               If the disk image contains a separate /usr/ partition it may
               also be Verity protected, in which case the signature for the
               root hash may configured via a .usrhash.p7s file adjacent to
               the disk image. There's currently no option to configure the
               root hash signature for the /usr/ via the unit file directly.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 246.
    
           _RootVerity=_
               Takes the path to a data integrity (dm-verity) file. This
               option enables data integrity checks using dm-verity, if
               _RootImage=_ is used and a root-hash is passed and if the used
               image itself does not contain the integrity data. The
               integrity data must be matched by the root hash. If this
               option is not specified, but a file with the .verity suffix is
               found next to the image file, bearing otherwise the same name
               (except if the image has the .raw suffix, in which case the
               verity data file must not have it in its name), the verity
               data is read from it and automatically used.
    
               This option is supported only for disk images that contain a
               single file system, without an enveloping partition table.
               Images that contain a GPT partition table should instead
               include both root file system and matching Verity data in the
               same image, implementing the **Discoverable Partitions**
               **Specification******[1].
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 246._RootImagePolicy=_ , _MountImagePolicy=_ , _ExtensionImagePolicy=_
               Takes an image policy string as per systemd.image-policy(7) to
               use when mounting the disk images (DDI) specified in
               _RootImage=_ , _MountImage=_ , _ExtensionImage=_ , respectively. If not
               specified the following policy string is the default for
               _RootImagePolicy=_ and _MountImagePolicy_ :
    
                   root=verity+signed+encrypted+unprotected+absent: \
                           usr=verity+signed+encrypted+unprotected+absent: \
                           home=encrypted+unprotected+absent: \
                           srv=encrypted+unprotected+absent: \
                           tmp=encrypted+unprotected+absent: \
                           var=encrypted+unprotected+absent
    
               The default policy for _ExtensionImagePolicy=_ is:
    
                   root=verity+signed+encrypted+unprotected+absent: \
                           usr=verity+signed+encrypted+unprotected+absent
    
               Added in version 254.
    
           _MountAPIVFS=_
               Takes a boolean argument. If on, a private mount namespace for
               the unit's processes is created and the API file systems
               /proc/, /sys/, /dev/ and /run/ (as an empty "tmpfs") are
               mounted inside of it, unless they are already mounted. Note
               that this option has no effect unless used in conjunction with
               _RootDirectory=_ /_RootImage=_ as these four mounts are generally
               mounted in the host anyway, and unless the root directory is
               changed, the private mount namespace will be a 1:1 copy of the
               host's, and include these four mounts. Note that the /dev/
               file system of the host is bind mounted if this option is used
               without _PrivateDevices=_. To run the service with a private,
               minimal version of /dev/, combine this option with
               _PrivateDevices=_.
    
               In order to allow propagating mounts at runtime in a safe
               manner, /run/systemd/propagate/ on the host will be used to
               set up new mounts, and /run/host/incoming/ in the private
               namespace will be used as an intermediate step to store them
               before being moved to the final mount point.
    
               Added in version 233.
    
           _BindLogSockets=_
               Takes a boolean argument. If true, sockets from
               systemd-journald.socket(8) will be bind mounted into the mount
               namespace. This is particularly useful when a different
               instance of /run/ is employed, to make sure processes running
               in the namespace can still make use of sd-journal(3).
    
               This option is implied when _LogNamespace=_ is used, when
               _MountAPIVFS=yes_ , or when _PrivateDevices=yes_ is used in
               conjunction with either _RootDirectory=_ or _RootImage=_.
    
               Added in version 257.
    
           _ProtectProc=_
               Takes one of "noaccess", "invisible", "ptraceable" or
               "default" (which it defaults to). When set, this controls the
               "hidepid=" mount option of the "procfs" instance for the unit
               that controls which directories with process metainformation
               (/proc/_PID_) are visible and accessible: when set to "noaccess"
               the ability to access most of other users' process metadata in
               /proc/ is taken away for processes of the service. When set to
               "invisible" processes owned by other users are hidden from
               /proc/. If "ptraceable" all processes that cannot be
               **ptrace()** 'ed by a process are hidden to it. If "default" no
               restrictions on /proc/ access or visibility are made. For
               further details see **The /proc Filesystem******[2]. It is generally
               recommended to run most system services with this option set
               to "invisible". This option is implemented via file system
               namespacing, and thus cannot be used with services that shall
               be able to install mount points in the host file system
               hierarchy. Note that the root user is unaffected by this
               option, so to be effective it has to be used together with _User=_ or _DynamicUser=yes_ , and also without the
               "CAP_SYS_PTRACE" capability, which also allows a process to
               bypass this feature. It cannot be used for services that need
               to access metainformation about other users' processes. This
               option implies _MountAPIVFS=_.
    
               If the kernel does not support per-mount point **hidepid=** mount
               options this setting remains without effect, and the unit's
               processes will be able to access and see other process as if
               the option was not used.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 247.
    
           _ProcSubset=_
               Takes one of "all" (the default) and "pid". If "pid", all
               files and directories not directly associated with process
               management and introspection are made invisible in the /proc/
               file system configured for the unit's processes. This controls
               the "subset=" mount option of the "procfs" instance for the
               unit. For further details see **The /proc Filesystem******[2]. Note
               that Linux exposes various kernel APIs via /proc/, which are
               made unavailable with this setting. Since these APIs are used
               frequently this option is useful only in a few, specific
               cases, and is not suitable for most non-trivial programs.
    
               Much like _ProtectProc=_ above, this is implemented via file
               system mount namespacing, and hence the same restrictions
               apply: it is only available to system services, it disables
               mount propagation to the host mount table, and it implies
               _MountAPIVFS=_. Also, like _ProtectProc=_ this setting is
               gracefully disabled if the used kernel does not support the
               "subset=" mount option of "procfs".
    
               Added in version 247.
    
           _BindPaths=_ , _BindReadOnlyPaths=_
               Configures unit-specific bind mounts. A bind mount makes a
               particular file or directory available at an additional place
               in the unit's view of the file system. Any bind mounts created
               with this option are specific to the unit, and are not visible
               in the host's mount table. This option expects a whitespace
               separated list of bind mount definitions. Each definition
               consists of a colon-separated triple of source path,
               destination path and option string, where the latter two are
               optional. If only a source path is specified the source and
               destination is taken to be the same. The option string may be
               either "rbind" or "norbind" for configuring a recursive or
               non-recursive bind mount. If the destination path is omitted,
               the option string must be omitted too. Each bind mount
               definition may be prefixed with "-", in which case it will be
               ignored when its source path does not exist.
    
               _BindPaths=_ creates regular writable bind mounts (unless the
               source file system mount is already marked read-only), while
               _BindReadOnlyPaths=_ creates read-only bind mounts. These
               settings may be used more than once, each usage appends to the
               unit's list of bind mounts. If the empty string is assigned to
               either of these two options the entire list of bind mounts
               defined prior to this is reset. Note that, in this case, both
               read-only and regular bind mounts are reset, regardless which
               of the two settings is used.
    
               Using this option implies that a mount namespace is allocated
               for the unit, i.e. it implies the effect of _PrivateMounts=_
               (see below).
    
               This option is particularly useful when
               _RootDirectory=_ /_RootImage=_ is used. In this case, the source
               path refers to a path on the host file system, while the
               destination path refers to a path below the root directory of
               the unit.
    
               Note that the destination directory must exist or systemd must
               be able to create it. Thus, it is not possible to use those
               options for mount points nested underneath paths specified in
               _InaccessiblePaths=_ , or under /home/ and other protected
               directories if _ProtectHome=yes_ is specified.
               _TemporaryFileSystem=_ with ":ro" or _ProtectHome=tmpfs_ should be
               used instead.
    
               Added in version 233.
    
           _MountImages=_
               This setting is similar to _RootImage=_ in that it mounts a file
               system hierarchy from a block device node or loopback file,
               but the destination directory can be specified as well as
               mount options. This option expects a whitespace separated list
               of mount definitions. Each definition consists of a
               colon-separated tuple of source path and destination
               definitions, optionally followed by another colon and a list
               of mount options.
    
               Mount options may be defined as a single comma-separated list
               of options, in which case they will be implicitly applied to
               the root partition on the image, or a series of
               colon-separated tuples of partition name and mount options.
               Valid partition names and mount options are the same as for
               _RootImageOptions=_ setting described above.
    
               Each mount definition may be prefixed with "-", in which case
               it will be ignored when its source path does not exist. The
               source argument is a path to a block device node or regular
               file. If source or destination contain a ":", it needs to be
               escaped as "\:". The device node or file system image file
               needs to follow the same rules as specified for _RootImage=_.
               Any mounts created with this option are specific to the unit,
               and are not visible in the host's mount table.
    
               These settings may be used more than once, each usage appends
               to the unit's list of mount paths. If the empty string is
               assigned, the entire list of mount paths defined prior to this
               is reset.
    
               Note that the destination directory must exist or systemd must
               be able to create it. Thus, it is not possible to use those
               options for mount points nested underneath paths specified in
               _InaccessiblePaths=_ , or under /home/ and other protected
               directories if _ProtectHome=yes_ is specified.
    
               When _DevicePolicy=_ is set to "closed" or "strict", or set to
               "auto" and _DeviceAllow=_ is set, then this setting adds
               /dev/loop-control with **rw** mode, "block-loop" and
               "block-blkext" with **rwm** mode to _DeviceAllow=_. See
               systemd.resource-control(5) for the details about
               _DevicePolicy=_ or _DeviceAllow=_. Also, see _PrivateDevices=_
               below, as it may change the setting of _DevicePolicy=_.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 247.
    
           _ExtensionImages=_
               This setting is similar to _MountImages=_ in that it mounts a
               file system hierarchy from a block device node or loopback
               file, but instead of providing a destination path, an overlay
               will be set up. This option expects a whitespace separated
               list of mount definitions. Each definition consists of a
               source path, optionally followed by a colon and a list of
               mount options.
    
               A read-only OverlayFS will be set up on top of /usr/ and /opt/
               hierarchies for sysext images and /etc/ hierarchy for confext
               images. The order in which the images are listed will
               determine the order in which the overlay is laid down: images
               specified first to last will result in overlayfs layers bottom
               to top.
    
               Mount options may be defined as a single comma-separated list
               of options, in which case they will be implicitly applied to
               the root partition on the image, or a series of
               colon-separated tuples of partition name and mount options.
               Valid partition names and mount options are the same as for
               _RootImageOptions=_ setting described above.
    
               Each mount definition may be prefixed with "-", in which case
               it will be ignored when its source path does not exist. The
               source argument is a path to a block device node or regular
               file. If the source path contains a ":", it needs to be
               escaped as "\:". The device node or file system image file
               needs to follow the same rules as specified for _RootImage=_.
               Any mounts created with this option are specific to the unit,
               and are not visible in the host's mount table.
    
               These settings may be used more than once, each usage appends
               to the unit's list of image paths. If the empty string is
               assigned, the entire list of mount paths defined prior to this
               is reset.
    
               Each sysext image must carry a
               /usr/lib/extension-release.d/extension-release.IMAGE file
               while each confext image must carry a
               /etc/extension-release.d/extension-release.IMAGE file, with
               the appropriate metadata which matches
               _RootImage=_ /_RootDirectory=_ or the host. See: os-release(5). To
               disable the safety check that the extension-release file name
               matches the image file name, the
               _x-systemd.relax-extension-release-check_ mount option may be
               appended.
    
               This option can be used together with a **notify-reload** service
               type and systemd.v(7) to manage configuration updates. When
               such a service carrying confext images is reloaded via
               **systemctl reload foo.service** or equivalent D-Bus method, the
               confext itself will be reloaded to pick up any changes. This
               only applies to confext extensions. Note that in case a
               service has this configuration enabled at first, and then it
               is subsequently removed in an update followed by a
               daemon-reload operation, reloading the confexts will be a
               no-op, and a full service restart is required instead. See
               systemd.service(5) also for details.
    
               When _DevicePolicy=_ is set to "closed" or "strict", or set to
               "auto" and _DeviceAllow=_ is set, then this setting adds
               /dev/loop-control with **rw** mode, "block-loop" and
               "block-blkext" with **rwm** mode to _DeviceAllow=_. See
               systemd.resource-control(5) for the details about
               _DevicePolicy=_ or _DeviceAllow=_. Also, see _PrivateDevices=_
               below, as it may change the setting of _DevicePolicy=_.
    
               In place of the image path a ".v/" versioned directory may be
               specified, see systemd.v(7) for details.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 248.
    
           _ExtensionDirectories=_
               This setting is similar to _BindReadOnlyPaths=_ in that it
               mounts a file system hierarchy from a directory, but instead
               of providing a destination path, an overlay will be set up.
               This option expects a whitespace separated list of source
               directories.
    
               A read-only OverlayFS will be set up on top of /usr/ and /opt/
               hierarchies for sysext images and /etc/ hierarchy for confext
               images. The order in which the directories are listed will
               determine the order in which the overlay is laid down:
               directories specified first to last will result in overlayfs
               layers bottom to top.
    
               Each directory listed in _ExtensionDirectories=_ may be prefixed
               with "-", in which case it will be ignored when its source
               path does not exist. Any mounts created with this option are
               specific to the unit, and are not visible in the host's mount
               table.
    
               These settings may be used more than once, each usage appends
               to the unit's list of directories paths. If the empty string
               is assigned, the entire list of mount paths defined prior to
               this is reset.
    
               Each sysext directory must contain a
               /usr/lib/extension-release.d/extension-release.IMAGE file
               while each confext directory must carry a
               /etc/extension-release.d/extension-release.IMAGE file, with
               the appropriate metadata which matches
               _RootImage=_ /_RootDirectory=_ or the host. See: os-release(5).
    
               This option can be used together with a **notify-reload** service
               type and systemd.v(7) to manage configuration updates. When
               such a service carrying confext directories is reloaded via
               **systemctl reload foo.service** or equivalent D-Bus method, the
               confext itself will be reloaded to pick up any changes. This
               only applies to confext extensions. Note that in case a
               service has this configuration enabled at first, and then it
               is subsequently removed in an update followed by a
               daemon-reload operation, reloading the confexts will be a
               no-op, and a full service restart is required instead. See
               systemd.service(5) also for details.
    
               Note that usage from user units requires overlayfs support in
               unprivileged user namespaces, which was first introduced in
               kernel v5.11.
    
               In place of the directory path a ".v/" versioned directory may
               be specified, see systemd.v(7) for details.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 251.
    


## USER/GROUP IDENTITY



           These options are only available for system services and are not
           supported for services running in per-user instances of the
           service manager.
    
           _User=_ , _Group=_
               Set the UNIX user or group that the processes are executed as,
               respectively. Takes a single user or group name, or a numeric
               ID as argument. For system services (services run by the
               system service manager, i.e. managed by PID 1) and for user
               services of the root user (services managed by root's instance
               of **systemd --user**), the default is "root", but _User=_ may be
               used to specify a different user. For user services of any
               other user, switching user identity is not permitted, hence
               the only valid setting is the same user the user's service
               manager is running as. If no group is set, the default group
               of the user is used. This setting does not affect commands
               whose command line is prefixed with "+".
    
               Note that this enforces only weak restrictions on the
               user/group name syntax, but will generate warnings in many
               cases where user/group names do not adhere to the following
               rules: the specified name should consist only of the
               characters a-z, A-Z, 0-9, "_" and "-", except for the first
               character which must be one of a-z, A-Z and "_" (i.e. digits
               and "-" are not permitted as first character). The user/group
               name must have at least one character, and at most 31. These
               restrictions are made in order to avoid ambiguities and to
               ensure user/group names and unit files remain portable among
               Linux systems. For further details on the names accepted and
               the names warned about see **User/Group Name Syntax******[3].
    
               When used in conjunction with _DynamicUser=_ the user/group name
               specified is dynamically allocated at the time the service is
               started, and released at the time the service is stopped —
               unless it is already allocated statically (see below). If
               _DynamicUser=_ is not used the specified user and group must
               have been created statically in the user database no later
               than the moment the service is started, for example using the
               sysusers.d(5) facility, which is applied at boot or package
               install time. If the user does not exist by then program
               invocation will fail.
    
               If the _User=_ setting is used the supplementary group list is
               initialized from the specified user's default group list, as
               defined in the system's user and group database. Additional
               groups may be configured through the _SupplementaryGroups=_
               setting (see below).
    
           _DynamicUser=_
               Takes a boolean parameter. If set, a UNIX user and group pair
               is allocated dynamically when the unit is started, and
               released as soon as it is stopped. The user and group will not
               be added to /etc/passwd or /etc/group, but are managed
               transiently during runtime. The nss-systemd(8) glibc NSS
               module provides integration of these dynamic users/groups into
               the system's user and group databases. The user and group name
               to use may be configured via _User=_ and _Group=_ (see above). If
               these options are not used and dynamic user/group allocation
               is enabled for a unit, the name of the dynamic user/group is
               implicitly derived from the unit name. If the unit name
               without the type suffix qualifies as valid user name it is
               used directly, otherwise a name incorporating a hash of it is
               used. If a statically allocated user or group of the
               configured name already exists, it is used and no dynamic
               user/group is allocated. Note that if _User=_ is specified and
               the static group with the name exists, then it is required
               that the static user with the name already exists. Similarly,
               if _Group=_ is specified and the static user with the name
               exists, then it is required that the static group with the
               name already exists. Dynamic users/groups are allocated from
               the UID/GID range 61184...65519. It is recommended to avoid
               this range for regular system or login users. At any point in
               time each UID/GID from this range is only assigned to zero or
               one dynamically allocated users/groups in use. However,
               UID/GIDs are recycled after a unit is terminated. Care should
               be taken that any processes running as part of a unit for
               which dynamic users/groups are enabled do not leave files or
               directories owned by these users/groups around, as a different
               unit might get the same UID/GID assigned later on, and thus
               gain access to these files or directories. If _DynamicUser=_ is
               enabled, _RemoveIPC=_ is implied (and cannot be turned off).
               This ensures that the lifetime of IPC objects and temporary
               files created by the executed processes is bound to the
               runtime of the service, and hence the lifetime of the dynamic
               user/group. Since /tmp/ and /var/tmp/ are usually the only
               world-writable directories on a system, unless _PrivateTmp=_ is
               manually set to "true", "disconnected" would be implied. This
               ensures that a unit making use of dynamic user/group
               allocation cannot leave files around after unit termination.
               Furthermore _NoNewPrivileges=_ and _RestrictSUIDSGID=_ are
               implicitly enabled (and cannot be disabled), to ensure that
               processes invoked cannot take benefit or create SUID/SGID
               files or directories. Moreover, _ProtectSystem=strict_ and
               _ProtectHome=read-only_ are implied, thus prohibiting the
               service to write to arbitrary file system locations. In order
               to allow the service to write to certain directories, they
               have to be allow-listed using _ReadWritePaths=_ , but care must
               be taken so that UID/GID recycling does not create security
               issues involving files created by the service. Use
               _RuntimeDirectory=_ (see below) in order to assign a writable
               runtime directory to a service, owned by the dynamic
               user/group and removed automatically when the unit is
               terminated. Use _StateDirectory=_ , _CacheDirectory=_ and
               _LogsDirectory=_ in order to assign a set of writable
               directories for specific purposes to the service in a way that
               they are protected from vulnerabilities due to UID reuse (see
               below). If this option is enabled, care should be taken that
               the unit's processes do not get access to directories outside
               of these explicitly configured and managed ones. Specifically,
               do not use _BindPaths=_ and be careful with **AF_UNIX** file
               descriptor passing for directory file descriptors, as this
               would permit processes to create files or directories owned by
               the dynamic user/group that are not subject to the lifecycle
               and access guarantees of the service. Note that this option is
               currently incompatible with D-Bus policies, thus a service
               using this option may currently not allocate a D-Bus service
               name (note that this does not affect calling into other D-Bus
               services). Defaults to off.
    
               Added in version 232.
    
           _SupplementaryGroups=_
               Sets the supplementary Unix groups the processes are executed
               as. This takes a space-separated list of group names or IDs.
               This option may be specified more than once, in which case all
               listed groups are set as supplementary groups. When the empty
               string is assigned, the list of supplementary groups is reset,
               and all assignments prior to this one will have no effect. In
               any way, this option does not override, but extends the list
               of supplementary groups configured in the system group
               database for the user. This does not affect commands prefixed
               with "+".
    
           _SetLoginEnvironment=_
               Takes a boolean parameter that controls whether to set the
               _$HOME_ , _$LOGNAME_ , and _$SHELL_ environment variables. If not set,
               this defaults to true if _User=_ , _DynamicUser=_ or _PAMName=_ are
               set, false otherwise. If set to true, the variables will
               always be set for system services, i.e. even when the default
               user "root" is used. If set to false, the mentioned variables
               are not set by the service manager, no matter whether _User=_ ,
               _DynamicUser=_ , or _PAMName=_ are used or not. This option
               normally has no effect on services of the per-user service
               manager, since in that case these variables are typically
               inherited from user manager's own environment anyway.
    
               Added in version 255.
    
           _PAMName=_
               Sets the PAM service name to set up a session as. If set, the
               executed process will be registered as a PAM session under the
               specified service name. This is only useful in conjunction
               with the _User=_ setting, and is otherwise ignored. If not set,
               no PAM session will be opened for the executed processes. See
               pam(8) for details.
    
               Note that for each unit making use of this option a PAM
               session handler process will be maintained as part of the unit
               and stays around as long as the unit is active, to ensure that
               appropriate actions can be taken when the unit and hence the
               PAM session terminates. This process is named "(sd-pam)" and
               is an immediate child process of the unit's main process.
    
               Note that when this option is used for a unit it is very
               likely (depending on PAM configuration) that the main unit
               process will be migrated to its own session scope unit when it
               is activated. This process will hence be associated with two
               units: the unit it was originally started from (and for which
               _PAMName=_ was configured), and the session scope unit. Any
               child processes of that process will however be associated
               with the session scope unit only. This has implications when
               used in combination with _NotifyAccess=_**all** , as these child
               processes will not be able to affect changes in the original
               unit through notification messages. These messages will be
               considered belonging to the session scope unit and not the
               original unit. It is hence not recommended to use _PAMName=_ in
               combination with _NotifyAccess=_**all**.
    
               If a PAM module interactively requests input (a password or
               suchlike) it will be attempted to be read from a service
               credential (as configured via _SetCredential=_ ,
               _ImportCredential=_ and related calls) under the name
               _pam.authtok.pamservice_ , where _pamservice_ is replaced by the
               PAM service name as configured with _PAMName=_. (Note that the
               credential remains accessible for the runtime of the service!)
               If no matching credential is set, the user is prompted for it
               interactively via the **Password Agent******[4] logic.


## CAPABILITIES



           These options are only available for system services, or for
           services running in per-user instances of the service manager in
           which case _PrivateUsers=_ is implicitly enabled (requires
           unprivileged user namespaces support to be enabled in the kernel
           via the "kernel.unprivileged_userns_clone=" sysctl).
    
           _CapabilityBoundingSet=_
               Controls which capabilities to include in the capability
               bounding set for the executed process. See capabilities(7) for
               details. Takes a whitespace-separated list of capability
               names, e.g.  **CAP_SYS_ADMIN** , **CAP_DAC_OVERRIDE** , **CAP_SYS_PTRACE**.
               Capabilities listed will be included in the bounding set, all
               others are removed. If the list of capabilities is prefixed
               with "~", all but the listed capabilities will be included,
               the effect of the assignment inverted. Note that this option
               also affects the respective capabilities in the effective,
               permitted and inheritable capability sets. If this option is
               not used, the capability bounding set is not modified on
               process execution, hence no limits on the capabilities of the
               process are enforced. This option may appear more than once,
               in which case the bounding sets are merged by **OR** , or by **AND** if
               the lines are prefixed with "~" (see below). If the empty
               string is assigned to this option, the bounding set is reset
               to the empty capability set, and all prior settings have no
               effect. If set to "~" (without any further argument), the
               bounding set is reset to the full set of available
               capabilities, also undoing any previous settings. This does
               not affect commands prefixed with "+".
    
               Use systemd-analyze(1)'s **capability** command to retrieve a list
               of capabilities defined on the local system.
    
               Example: if a unit has the following,
    
                   CapabilityBoundingSet=CAP_A CAP_B
                   CapabilityBoundingSet=CAP_B CAP_C
    
               then **CAP_A** , **CAP_B** , and **CAP_C** are set. If the second line is
               prefixed with "~", e.g.,
    
                   CapabilityBoundingSet=CAP_A CAP_B
                   CapabilityBoundingSet=~CAP_B CAP_C
    
               then, only **CAP_A** is set.
    
           _AmbientCapabilities=_
               Controls which capabilities to include in the ambient
               capability set for the executed process. Takes a
               whitespace-separated list of capability names, e.g.
               **CAP_SYS_ADMIN** , **CAP_DAC_OVERRIDE** , **CAP_SYS_PTRACE**. This option
               may appear more than once, in which case the ambient
               capability sets are merged (see the above examples in
               _CapabilityBoundingSet=_). If the list of capabilities is
               prefixed with "~", all but the listed capabilities will be
               included, the effect of the assignment inverted. If the empty
               string is assigned to this option, the ambient capability set
               is reset to the empty capability set, and all prior settings
               have no effect. If set to "~" (without any further argument),
               the ambient capability set is reset to the full set of
               available capabilities, also undoing any previous settings.
               Note that adding capabilities to the ambient capability set
               adds them to the process's inherited capability set.
    
               Ambient capability sets are useful if you want to execute a
               process as a non-privileged user but still want to give it
               some capabilities. Note that, in this case, option **keep-caps**
               is automatically added to _SecureBits=_ to retain the
               capabilities over the user change.  _AmbientCapabilities=_ does
               not affect commands prefixed with "+".
    
               Added in version 229.
    


## SECURITY



           _NoNewPrivileges=_
               Takes a boolean argument. If true, ensures that the service
               process and all its children can never gain new privileges
               through **execve()**(e.g. via setuid or setgid bits, or
               filesystem capabilities). This is the simplest and most
               effective way to ensure that a process and its children can
               never elevate privileges again. Defaults to false. In case the
               service will be run in a new mount namespace anyway and
               SELinux is disabled, all file systems are mounted with
               **MS_NOSUID** flag. Also see **No New Privileges Flag******[5].
    
               Note that this setting only has an effect on the unit's
               processes themselves (or any processes directly or indirectly
               forked off them). It has no effect on processes potentially
               invoked on request of them through tools such as**at**(1),
               crontab(1), systemd-run(1), or arbitrary IPC services.
    
               Added in version 187.
    
           _SecureBits=_
               Controls the secure bits set for the executed process. Takes a
               space-separated combination of options from the following
               list: **keep-caps** , **keep-caps-locked** , **no-setuid-fixup** ,
               **no-setuid-fixup-locked** , **noroot** , and **noroot-locked**. This option
               may appear more than once, in which case the secure bits are
               ORed. If the empty string is assigned to this option, the bits
               are reset to 0. This does not affect commands prefixed with
               "+". See capabilities(7) for details.
    


## MANDATORY ACCESS CONTROL



           _SELinuxContext=_
               Set the SELinux security context of the executed process. If
               set, this will override the automated domain transition.
               However, the policy still needs to authorize the transition.
               This directive is ignored if SELinux is disabled. If prefixed
               by "-", failing to set the SELinux security context will be
               ignored, but it is still possible that the subsequent **execve()**
               may fail if the policy does not allow the transition for the
               non-overridden context. This does not affect commands prefixed
               with "+". See setexeccon(3) for details.
    
               Added in version 209.
    
           _AppArmorProfile=_
               Takes a profile name as argument. The process executed by the
               unit will switch to this profile when started. Profiles must
               already be loaded in the kernel, or the unit will fail. If
               prefixed by "-", all errors will be ignored. This setting has
               no effect if AppArmor is not enabled. This setting does not
               affect commands prefixed with "+".
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 210.
    
           _SmackProcessLabel=_
               Takes a **SMACK64** security label as argument. The process
               executed by the unit will be started under this label and
               SMACK will decide whether the process is allowed to run or
               not, based on it. The process will continue to run under the
               label specified here unless the executable has its own
               **SMACK64EXEC** label, in which case the process will transition
               to run under that label. When not specified, the label that
               systemd is running under is used. This directive is ignored if
               SMACK is disabled.
    
               The value may be prefixed by "-", in which case all errors
               will be ignored. An empty value may be specified to unset
               previous assignments. This does not affect commands prefixed
               with "+".
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 218.
    


## PROCESS PROPERTIES



           _LimitCPU=_ , _LimitFSIZE=_ , _LimitDATA=_ , _LimitSTACK=_ , _LimitCORE=_ ,
           _LimitRSS=_ , _LimitNOFILE=_ , _LimitAS=_ , _LimitNPROC=_ , _LimitMEMLOCK=_ ,
           _LimitLOCKS=_ , _LimitSIGPENDING=_ , _LimitMSGQUEUE=_ , _LimitNICE=_ ,
           _LimitRTPRIO=_ , _LimitRTTIME=_
               Set soft and hard limits on various resources for executed
               processes. See setrlimit(2) for details on the process
               resource limit concept. Process resource limits may be
               specified in two formats: either as single value to set a
               specific soft and hard limit to the same value, or as
               colon-separated pair **soft:hard** to set both limits individually
               (e.g.  "LimitAS=4G:16G"). Use the string **infinity** to configure
               no limit on a specific resource. The multiplicative suffixes
               K, M, G, T, P and E (to the base 1024) may be used for
               resource limits measured in bytes (e.g.  "LimitAS=16G"). For
               the limits referring to time values, the usual time units ms,
               s, min, h and so on may be used (see systemd.time(7) for
               details). Note that if no time unit is specified for _LimitCPU=_
               the default unit of seconds is implied, while for _LimitRTTIME=_
               the default unit of microseconds is implied. Also, note that
               the effective granularity of the limits might influence their
               enforcement. For example, time limits specified for _LimitCPU=_
               will be rounded up implicitly to multiples of 1s. For
               _LimitNICE=_ the value may be specified in two syntaxes: if
               prefixed with "+" or "-", the value is understood as regular
               Linux nice value in the range -20...19. If not prefixed like
               this the value is understood as raw resource limit parameter
               in the range 0...40 (with 0 being equivalent to 1).
    
               Note that most process resource limits configured with these
               options are per-process, and processes may fork in order to
               acquire a new set of resources that are accounted
               independently of the original process, and may thus escape
               limits set. Also note that _LimitRSS=_ is not implemented on
               Linux, and setting it has no effect. Often it is advisable to
               prefer the resource controls listed in
               systemd.resource-control(5) over these per-process limits, as
               they apply to services as a whole, may be altered dynamically
               at runtime, and are generally more expressive. For example,
               _MemoryMax=_ is a more powerful (and working) replacement for
               _LimitRSS=_.
    
               Note that _LimitNPROC=_ will limit the number of processes from
               one (real) UID and not the number of processes started
               (forked) by the service. Therefore the limit is cumulative for
               all processes running under the same UID. Please also note
               that the _LimitNPROC=_ will not be enforced if the service is
               running as root (and not dropping privileges). Due to these
               limitations, _TasksMax=_ (see systemd.resource-control(5)) is
               typically a better choice than _LimitNPROC=_.
    
               Resource limits not configured explicitly for a unit default
               to the value configured in the various _DefaultLimitCPU=_ ,
               _DefaultLimitFSIZE=_ , ... options available in
               systemd-system.conf(5), and – if not configured there – the
               kernel or per-user defaults, as defined by the OS (the latter
               only for user services, see below).
    
               For system units these resource limits may be chosen freely.
               When these settings are configured in a user service (i.e. a
               service run by the per-user instance of the service manager)
               they cannot be used to raise the limits above those set for
               the user manager itself when it was first invoked, as the
               user's service manager generally lacks the privileges to do
               so. In user context these configuration options are hence only
               useful to lower the limits passed in or to raise the soft
               limit to the maximum of the hard limit as configured for the
               user. To raise the user's limits further, the available
               configuration mechanisms differ between operating systems, but
               typically require privileges. In most cases it is possible to
               configure higher per-user resource limits via PAM or by
               setting limits on the system service encapsulating the user's
               service manager, i.e. the user's instance of user@.service.
               After making such changes, make sure to restart the user's
               service manager.
    
               **Table 1. Resource limit directives, their equivalent ulimit**
               **shell commands and the unit used**
               ┌──────────────────┬────────────┬─────────────────┬──────────────────────────────┐
               │ **Directive** │ **ulimit** │ **Unit** │ **Notes** │
               │                  │ equivalent │                 │                              │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitCPU=        │ ulimit -t  │ Seconds         │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitFSIZE=      │ ulimit -f  │ Bytes           │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitDATA=       │ ulimit -d  │ Bytes           │ Do not use.                  │
               │                  │            │                 │ This limits the              │
               │                  │            │                 │ allowed address              │
               │                  │            │                 │ range, not                   │
               │                  │            │                 │ memory use!                  │
               │                  │            │                 │ Defaults to                  │
               │                  │            │                 │ unlimited and                │
               │                  │            │                 │ should not be                │
               │                  │            │                 │ lowered. To                  │
               │                  │            │                 │ limit memory                 │
               │                  │            │                 │ use, see                     │
               │                  │            │                 │ _MemoryMax=_ in                │
               │                  │            │                 │ systemd.resource-control(5). │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitSTACK=      │ ulimit -s  │ Bytes           │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitCORE=       │ ulimit -c  │ Bytes           │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitRSS=        │ ulimit -m  │ Bytes           │ Do not use. No effect on     │
               │                  │            │                 │ Linux.                       │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitNOFILE=     │ ulimit -n  │ Number of File  │ Do not use. Be careful when  │
               │                  │            │ Descriptors     │ raising the soft limit above │
               │                  │            │                 │ 1024, since select(2) cannot │
               │                  │            │                 │ function with file           │
               │                  │            │                 │ descriptors above 1023 on    │
               │                  │            │                 │ Linux. Nowadays, the hard    │
               │                  │            │                 │ limit defaults to 524288, a  │
               │                  │            │                 │ very high value compared to  │
               │                  │            │                 │ historical defaults.         │
               │                  │            │                 │ Typically applications       │
               │                  │            │                 │ should increase their soft   │
               │                  │            │                 │ limit to the hard limit on   │
               │                  │            │                 │ their own, if they are OK    │
               │                  │            │                 │ with working with file       │
               │                  │            │                 │ descriptors above 1023, i.e. │
               │                  │            │                 │ do not use select(2). Note   │
               │                  │            │                 │ that file descriptors are    │
               │                  │            │                 │ nowadays accounted like any  │
               │                  │            │                 │ other form of memory, thus   │
               │                  │            │                 │ there should not be any need │
               │                  │            │                 │ to lower the hard limit. Use │
               │                  │            │                 │ _MemoryMax=_ to control        │
               │                  │            │                 │ overall service memory use,  │
               │                  │            │                 │ including file descriptor    │
               │                  │            │                 │ memory.                      │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitAS=         │ ulimit -v  │ Bytes           │ Do not use. This limits the  │
               │                  │            │                 │ allowed address range, not   │
               │                  │            │                 │ memory use! Defaults to      │
               │                  │            │                 │ unlimited and should not be  │
               │                  │            │                 │ lowered. To limit memory     │
               │                  │            │                 │ use, see _MemoryMax=_ in       │
               │                  │            │                 │ systemd.resource-control(5). │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitNPROC=      │ ulimit -u  │ Number of       │ This limit is enforced based │
               │                  │            │ Processes       │ on the number of processes   │
               │                  │            │                 │ belonging to the user.       │
               │                  │            │                 │ Typically it is better to    │
               │                  │            │                 │ track processes per service, │
               │                  │            │                 │ i.e. use _TasksMax=_ , see      │
               │                  │            │                 │ systemd.resource-control(5). │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitMEMLOCK=    │ ulimit -l  │ Bytes           │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitLOCKS=      │ ulimit -x  │ Number of Locks │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitSIGPENDING= │ ulimit -i  │ Number of       │ -                            │
               │                  │            │ Queued Signals  │                              │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitMSGQUEUE=   │ ulimit -q  │ Bytes           │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitNICE=       │ ulimit -e  │ Nice Level      │ -                            │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitRTPRIO=     │ ulimit -r  │ Realtime        │ -                            │
               │                  │            │ Priority        │                              │
               ├──────────────────┼────────────┼─────────────────┼──────────────────────────────┤
               │ LimitRTTIME=     │ ulimit -R  │ Microseconds    │ -                            │
               └──────────────────┴────────────┴─────────────────┴──────────────────────────────┘
    
           _UMask=_
               Controls the file mode creation mask. Takes an access mode in
               octal notation. See umask(2) for details. Defaults to 0022 for
               system units. For user units the default value is inherited
               from the per-user service manager (whose default is in turn
               inherited from the system service manager, and thus typically
               also is 0022 — unless overridden by a PAM module). In order to
               change the per-user mask for all user services, consider
               setting the _UMask=_ setting of the user's user@.service system
               service instance. The per-user umask may also be set via the
               _umask_ field of a user's **JSON User Record******[6] (for users managed
               bysystemd-homed.service(8) this field may be controlled via
               **homectl --umask=**). It may also be set via a PAM module, such
               as pam_umask(8).
    
           _CoredumpFilter=_
               Controls which types of memory mappings will be saved if the
               process dumps core (using the /proc/_pid_ /coredump_filter file).
               Takes a whitespace-separated combination of mapping type names
               or numbers (with the default base 16). Mapping type names are
               **private-anonymous** , **shared-anonymous** , **private-file-backed** ,
               **shared-file-backed** , **elf-headers** , **private-huge** , **shared-huge** ,
               **private-dax** , **shared-dax** , and the special values **all**(all
               types) and **default**(the kernel default of "**private-anonymous**
               **shared-anonymous elf-headers private-huge** "). See core(5) for
               the meaning of the mapping types. When specified multiple
               times, all specified masks are ORed. When not set, or if the
               empty value is assigned, the inherited value is not changed.
    
               **Example 2. Add DAX pages to the dump filter**
    
                   CoredumpFilter=default private-dax shared-dax
    
               Added in version 246.
    
           _KeyringMode=_
               Controls how the kernel session keyring is set up for the
               service (see session-keyring(7) for details on the session
               keyring). Takes one of **inherit** , **private** , **shared**. If set to
               **inherit** no special keyring setup is done, and the kernel's
               default behaviour is applied. If **private** is used a new session
               keyring is allocated when a service process is invoked, and it
               is not linked up with any user keyring. This is the
               recommended setting for system services, as this ensures that
               multiple services running under the same system user ID (in
               particular the root user) do not share their key material
               among each other. If **shared** is used a new session keyring is
               allocated as for **private** , but the user keyring of the user
               configured with _User=_ is linked into it, so that keys assigned
               to the user may be requested by the unit's processes. In this
               mode multiple units running processes under the same user ID
               may share key material. Unless **inherit** is selected the unique
               invocation ID for the unit (see below) is added as a protected
               key by the name "invocation_id" to the newly created session
               keyring. Defaults to **private** for services of the system
               service manager and to **inherit** for non-service units and for
               services of the user service manager.
    
               Added in version 235.
    
           _OOMScoreAdjust=_
               Sets the adjustment value for the Linux kernel's Out-Of-Memory
               (OOM) killer score for executed processes. Takes an integer
               between -1000 (to disable OOM killing of processes of this
               unit) and 1000 (to make killing of processes of this unit
               under memory pressure very likely). See **The /proc**
               **Filesystem******[7] for details. If not specified, defaults to the
               OOM score adjustment level of the service manager itself,
               which is normally at 0.
    
               Use the _OOMPolicy=_ setting of service units to configure how
               the service manager shall react to the kernel OOM killer or
               **systemd-oomd** terminating a process of the service. See
               systemd.service(5) for details.
    
           _TimerSlackNSec=_
               Sets the timer slack in nanoseconds for the executed
               processes. The timer slack controls the accuracy of wake-ups
               triggered by timers. See prctl(2) for more information. Note
               that in contrast to most other time span definitions this
               parameter takes an integer value in nano-seconds if no unit is
               specified. The usual time units are understood too.
    
           _Personality=_
               Controls which kernel architecture uname(2) shall report, when
               invoked by unit processes. Takes one of the architecture
               identifiers **arm64** , **arm64-be** , **arm** , **arm-be** , **x86** , **x86-64** , **ppc** ,
               **ppc-le** , **ppc64** , **ppc64-le** , **s390** or **s390x**. Which personality
               architectures are supported depends on the kernel's native
               architecture. Usually the 64-bit versions of the various
               system architectures support their immediate 32-bit
               personality architecture counterpart, but no others. For
               example, **x86-64** systems support the **x86-64** and **x86**
               personalities but no others. The personality feature is useful
               when running 32-bit services on a 64-bit host system. If not
               specified, the personality is left unmodified and thus
               reflects the personality of the host system's kernel. This
               option is not useful on architectures for which only one
               native word width was ever available, such as **m68k**(32-bit
               only) or **alpha**(64-bit only).
    
               Added in version 209.
    
           _IgnoreSIGPIPE=_
               Takes a boolean argument. If true, **SIGPIPE** is ignored in the
               executed process. Defaults to true since **SIGPIPE** is generally
               only useful in shell pipelines.
    


## SCHEDULING



           _Nice=_
               Sets the default nice level (scheduling priority) for executed
               processes. Takes an integer between -20 (highest priority) and
               19 (lowest priority). In case of resource contention, smaller
               values mean more resources will be made available to the
               unit's processes, larger values mean less resources will be
               made available. See setpriority(2) for details.
    
           _CPUSchedulingPolicy=_
               Sets the CPU scheduling policy for executed processes. Takes
               one of **other** , **batch** , **idle** , **fifo** or **rr**. See
               sched_setscheduler(2) for details.
    
           _CPUSchedulingPriority=_
               Sets the CPU scheduling priority for executed processes. The
               available priority range depends on the selected CPU
               scheduling policy (see above). For real-time scheduling
               policies an integer between 1 (lowest priority) and 99
               (highest priority) can be used. In case of CPU resource
               contention, smaller values mean less CPU time is made
               available to the service, larger values mean more. See
               sched_setscheduler(2) for details.
    
           _CPUSchedulingResetOnFork=_
               Takes a boolean argument. If true, elevated CPU scheduling
               priorities and policies will be reset when the executed
               processes call fork(2), and can hence not leak into child
               processes. See sched_setscheduler(2) for details. Defaults to
               false.
    
           _CPUAffinity=_
               Controls the CPU affinity of the executed processes. Takes a
               list of CPU indices or ranges separated by either whitespace
               or commas. Alternatively, takes a special "numa" value in
               which case systemd automatically derives allowed CPU range
               based on the value of _NUMAMask=_ option. CPU ranges are
               specified by the lower and upper CPU indices separated by a
               dash. This option may be specified more than once, in which
               case the specified CPU affinity masks are merged. If the empty
               string is assigned, the mask is reset, all assignments prior
               to this will have no effect. See sched_setaffinity(2) for
               details.
    
           _NUMAPolicy=_
               Controls the NUMA memory policy of the executed processes.
               Takes a policy type, one of: **default** , **preferred** , **bind** ,
               **interleave** and **local**. A list of NUMA nodes that should be
               associated with the policy must be specified in _NUMAMask=_. For
               more details on each policy please see, set_mempolicy(2). For
               overall overview of NUMA support in Linux see, numa(7).
    
               Added in version 243.
    
           _NUMAMask=_
               Controls the NUMA node list which will be applied alongside
               with selected NUMA policy. Takes a list of NUMA nodes and has
               the same syntax as a list of CPUs for _CPUAffinity=_ option or
               special "all" value which will include all available NUMA
               nodes in the mask. Note that the list of NUMA nodes is not
               required for **default** and **local** policies and for **preferred**
               policy we expect a single NUMA node.
    
               Added in version 243.
    
           _IOSchedulingClass=_
               Sets the I/O scheduling class for executed processes. Takes
               one of the strings **realtime** , **best-effort** or **idle**. The kernel's
               default scheduling class is **best-effort** at a priority of 4. If
               the empty string is assigned to this option, all prior
               assignments to both _IOSchedulingClass=_ and
               _IOSchedulingPriority=_ have no effect. See ioprio_set(2) for
               details.
    
           _IOSchedulingPriority=_
               Sets the I/O scheduling priority for executed processes. Takes
               an integer between 0 (highest priority) and 7 (lowest
               priority). In case of I/O contention, smaller values mean more
               I/O bandwidth is made available to the unit's processes,
               larger values mean less bandwidth. The available priorities
               depend on the selected I/O scheduling class (see above). If
               the empty string is assigned to this option, all prior
               assignments to both _IOSchedulingClass=_ and
               _IOSchedulingPriority=_ have no effect. For the kernel's default
               scheduling class (**best-effort**) this defaults to 4. See
               ioprio_set(2) for details.
    


## SANDBOXING



           The following sandboxing options are an effective way to limit the
           exposure of the system towards the unit's processes. It is
           recommended to turn on as many of these options for each unit as
           is possible without negatively affecting the process' ability to
           operate. Note that many of these sandboxing features are
           gracefully turned off on systems where the underlying security
           mechanism is not available. For example, _ProtectSystem=_ has no
           effect if the kernel is built without file system namespacing or
           if the service manager runs in a container manager that makes file
           system namespacing unavailable to its payload. Similarly,
           _RestrictRealtime=_ has no effect on systems that lack support for
           SECCOMP system call filtering, or in containers where support for
           this is turned off.
    
           Also note that some sandboxing functionality is generally not
           available in user services (i.e. services run by the per-user
           service manager). Specifically, the various settings requiring
           file system namespacing support (such as _ProtectSystem=_) are not
           available, as the underlying kernel functionality is only
           accessible to privileged processes. However, most namespacing
           settings, that will not work on their own in user services, will
           work when used in conjunction with _PrivateUsers=_**true**.
    
           Note that the various options that turn directories read-only
           (such as _ProtectSystem=_ , _ReadOnlyPaths=_ , ...) do not affect the
           ability for programs to connect to and communicate with **AF_UNIX**
           sockets in these directories. These options cannot be used to lock
           down access to IPC services hence.
    
           _ProtectSystem=_
               Takes a boolean argument or the special values "full" or
               "strict". If true, mounts the /usr/ and the boot loader
               directories (/boot and /efi) read-only for processes invoked
               by this unit. If set to "full", the /etc/ directory is mounted
               read-only, too. If set to "strict" the entire file system
               hierarchy is mounted read-only, except for the API file system
               subtrees /dev/, /proc/ and /sys/ (protect these directories
               using _PrivateDevices=_ , _ProtectKernelTunables=_ ,
               _ProtectControlGroups=_). This setting ensures that any
               modification of the vendor-supplied operating system (and
               optionally its configuration, and local mounts) is prohibited
               for the service. It is recommended to enable this setting for
               all long-running services, unless they are involved with
               system updates or need to modify the operating system in other
               ways. If this option is used, _ReadWritePaths=_ may be used to
               exclude specific directories from being made read-only.
               Similar, _StateDirectory=_ , _LogsDirectory=_ , ... and related
               directory settings (see below) also exclude the specific
               directories from the effect of _ProtectSystem=_. This setting is
               implied if _DynamicUser=_ is set. This setting cannot ensure
               protection in all cases. In general it has the same
               limitations as _ReadOnlyPaths=_ , see below. Defaults to off.
    
               Note that if _ProtectSystem=_ is set to "strict" and _PrivateTmp=_
               is enabled, then /tmp/ and /var/tmp/ will be writable.
    
               Added in version 214.
    
           _ProtectHome=_
               Takes a boolean argument or the special values "read-only" or
               "tmpfs". If true, the directories /home/, /root, and /run/user
               are made inaccessible and empty for processes invoked by this
               unit. If set to "read-only", the three directories are made
               read-only instead. If set to "tmpfs", temporary file systems
               are mounted on the three directories in read-only mode. The
               value "tmpfs" is useful to hide home directories not relevant
               to the processes invoked by the unit, while still allowing
               necessary directories to be made visible when listed in
               _BindPaths=_ or _BindReadOnlyPaths=_.
    
               Setting this to "yes" is mostly equivalent to setting the
               three directories in _InaccessiblePaths=_. Similarly,
               "read-only" is mostly equivalent to _ReadOnlyPaths=_ , and
               "tmpfs" is mostly equivalent to _TemporaryFileSystem=_ with
               ":ro".
    
               It is recommended to enable this setting for all long-running
               services (in particular network-facing ones), to ensure they
               cannot get access to private user data, unless the services
               actually require access to the user's private data. This
               setting is implied if _DynamicUser=_ is set. This setting cannot
               ensure protection in all cases. In general it has the same
               limitations as _ReadOnlyPaths=_ , see below.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 214.
    
           _RuntimeDirectory=_ , _StateDirectory=_ , _CacheDirectory=_ ,
           _LogsDirectory=_ , _ConfigurationDirectory=_
               These options take a whitespace-separated list of directory
               names. The specified directory names must be relative, and may
               not include "..". If set, when the unit is started, one or
               more directories by the specified names will be created
               (including their parents) below the locations defined in the
               following table. Also, the corresponding environment variable
               will be defined with the full paths of the directories. If
               multiple directories are set, then in the environment variable
               the paths are concatenated with colon (":").
    
               If _DynamicUser=_ is used, and if the kernel version supports
               **id-mapped mounts******[8], the specified directories will be owned
               by "nobody" in the host namespace and will be mapped to (and
               will be owned by) the service's UID/GID in its own namespace.
               For backward compatibility, existing directories created
               without id-mapped mounts will be kept untouched.**Table 2. Automatic directory creation and environment**
               **variables**
               ┌─────────────────────────┬────────────────┬──────────────────────┬──────────────────────────┐
               │ **Directory** │ **Below path for** │ **Below path for** │ **Environment** │
               │                         │ **system units** │ **user units** │ **variable set** │
               ├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
               │ _RuntimeDirectory=_       │ /run/          │ _$XDG_RUNTIME_DIR_     │ _$RUNTIME_DIRECTORY_       │
               ├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
               │ _StateDirectory=_         │ /var/lib/      │ _$XDG_STATE_HOME_      │ _$STATE_DIRECTORY_         │
               ├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
               │ _CacheDirectory=_         │ /var/cache/    │ _$XDG_CACHE_HOME_      │ _$CACHE_DIRECTORY_         │
               ├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
               │ _LogsDirectory=_          │ /var/log/      │ _$XDG_STATE_HOME_ /log/ │ _$LOGS_DIRECTORY_          │
               ├─────────────────────────┼────────────────┼──────────────────────┼──────────────────────────┤
               │ _ConfigurationDirectory=_ │ /etc/          │ _$XDG_CONFIG_HOME_     │ _$CONFIGURATION_DIRECTORY_ │
               └─────────────────────────┴────────────────┴──────────────────────┴──────────────────────────┘
    
               In case of _RuntimeDirectory=_ the innermost subdirectories are
               removed when the unit is stopped. It is possible to preserve
               the specified directories in this case if
               _RuntimeDirectoryPreserve=_ is configured to **restart** or **yes**(see
               below). The directories specified with _StateDirectory=_ ,
               _CacheDirectory=_ , _LogsDirectory=_ , _ConfigurationDirectory=_ are
               not removed when the unit is stopped.
    
               Except in case of _ConfigurationDirectory=_ , the innermost
               specified directories will be owned by the user and group
               specified in _User=_ and _Group=_. If the specified directories
               already exist and their owning user or group do not match the
               configured ones, all files and directories below the specified
               directories as well as the directories themselves will have
               their file ownership recursively changed to match what is
               configured. As an optimization, if the specified directories
               are already owned by the right user and group, files and
               directories below of them are left as-is, even if they do not
               match what is requested. The innermost specified directories
               will have their access mode adjusted to the what is specified
               in _RuntimeDirectoryMode=_ , _StateDirectoryMode=_ ,
               _CacheDirectoryMode=_ , _LogsDirectoryMode=_ and
               _ConfigurationDirectoryMode=_.
    
               These options imply _BindPaths=_ for the specified paths. When
               combined with _RootDirectory=_ or _RootImage=_ these paths always
               reside on the host and are mounted from there into the unit's
               file system namespace.
    
               If _DynamicUser=_ is used, the logic for _CacheDirectory=_ ,
               _LogsDirectory=_ and _StateDirectory=_ is slightly altered: the
               directories are created below /var/cache/private,
               /var/log/private and /var/lib/private, respectively, which are
               host directories made inaccessible to unprivileged users,
               which ensures that access to these directories cannot be
               gained through dynamic user ID recycling. Symbolic links are
               created to hide this difference in behaviour. Both from
               perspective of the host and from inside the unit, the relevant
               directories hence always appear directly below /var/cache,
               /var/log and /var/lib.
    
               Use _RuntimeDirectory=_ to manage one or more runtime
               directories for the unit and bind their lifetime to the daemon
               runtime. This is particularly useful for unprivileged daemons
               that cannot create runtime directories in /run/ due to lack of
               privileges, and to make sure the runtime directory is cleaned
               up automatically after use. For runtime directories that
               require more complex or different configuration or lifetime
               guarantees, please consider using tmpfiles.d(5).
    
               _RuntimeDirectory=_ , _StateDirectory=_ , _CacheDirectory=_ and
               _LogsDirectory=_ optionally support two more parameters,
               separated by ":". The second parameter will be interpreted as
               a destination path that will be created as a symlink to the
               directory. The symlinks will be created after any _BindPaths=_
               or _TemporaryFileSystem=_ options have been set up, to make
               ephemeral symlinking possible. The same source can have
               multiple symlinks, by using the same first parameter, but a
               different second parameter. The third parameter is a flags
               field, and since v257 can take a value of **ro** to make the
               directory read only for the service. This is also supported
               for _ConfigurationDirectory=_. If multiple symlinks are set up,
               the directory will be read only if at least one is configured
               to be read only. To pass a flag without a destination symlink,
               the second parameter can be empty, for example:
    
                   ConfigurationDirectory=foo::ro
    
               The directories defined by these options are always created
               under the standard paths used by systemd (/var/, /run/, /etc/,
               ...). If the service needs directories in a different
               location, a different mechanism has to be used to create them.
    
               tmpfiles.d(5) provides functionality that overlaps with these
               options. Using these options is recommended, because the
               lifetime of the directories is tied directly to the lifetime
               of the unit, and it is not necessary to ensure that the
               tmpfiles.d configuration is executed before the unit is
               started.
    
               To remove any of the directories created by these settings,
               use the **systemctl clean ...** command on the relevant units,
               see systemctl(1) for details.
    
               Example: if a system service unit has the following,
    
                   RuntimeDirectory=foo/bar baz
    
               the service manager creates /run/foo (if it does not exist),
               /run/foo/bar, and /run/baz. The directories /run/foo/bar and
               /run/baz except /run/foo are owned by the user and group
               specified in _User=_ and _Group=_ , and removed when the service is
               stopped.
    
               Example: if a system service unit has the following,
    
                   RuntimeDirectory=foo/bar
                   StateDirectory=aaa/bbb ccc
    
               then the environment variable "RUNTIME_DIRECTORY" is set with
               "/run/foo/bar", and "STATE_DIRECTORY" is set with
               "/var/lib/aaa/bbb:/var/lib/ccc".
    
               Example: if a system service unit has the following,
    
                   RuntimeDirectory=foo:bar foo:baz
    
               the service manager creates /run/foo (if it does not exist),
               and /run/bar plus /run/baz as symlinks to /run/foo.
    
               Added in version 211.
    
           _RuntimeDirectoryMode=_ , _StateDirectoryMode=_ , _CacheDirectoryMode=_ ,
           _LogsDirectoryMode=_ , _ConfigurationDirectoryMode=_
               Specifies the access mode of the directories specified in
               _RuntimeDirectory=_ , _StateDirectory=_ , _CacheDirectory=_ ,
               _LogsDirectory=_ , or _ConfigurationDirectory=_ , respectively, as
               an octal number. Defaults to **0755**. See "Permissions" in
               path_resolution(7) for a discussion of the meaning of
               permission bits.
    
               Added in version 234.
    
           _StateDirectoryQuota=_ , _CacheDirectoryQuota=_ , _LogsDirectoryQuota=_
               Specifies the storage limits for the directories specified in
               _StateDirectory=_ , _CacheDirectory=_ , or _LogsDirectory=_
               respectively.
    
               The storage quota is defined in terms of disk blocks and
               inodes, as per **quotactl******[9]. Takes an absolute size limit in
               bytes. If the value is suffixed with K, M, G or T, the
               specified size is parsed as Kilobytes, Megabytes, Gigabytes,
               or Terabytes (with the base 1024), respectively. If an
               absolute size limit is specified, only the block quota is set
               (rounded up to the nearest block). Alternatively, a percentage
               value may be specified, which applies the same percent quota
               to both blocks and inodes. Defaults to**off** , in which case no
               storage limits will be set.
    
               Only hard limits are set, not soft limits. If the underlying
               filesystem for the specified directories does not support
               project quotas, the specified storage limits will not be set.
               In addition to enabling per-unit quotas with these settings,
               it is necessary to enable **prjquota** on the file system level as
               well (i.e.  **tune2fs -Q prjquota**). Quotas must also be turned
               on with **quotaon.******[10]
    
               Added in version 258._StateDirectoryAccounting=_ , _CacheDirectoryAccounting=_ ,
           _LogsDirectoryAccounting=_
               Takes a boolean argument. If true, a project ID is assigned to
               the directories specified in _StateDirectory=_ , _CacheDirectory=_ ,
               or _LogsDirectory=_ respectively, which is used for tracking
               disk usage when disk quotas are turned on (see **repquota******[11]).
               Defaults to false.
    
               To set and enforce disk quotas,_StateDirectoryQuota=_ ,
               _CacheDirectoryQuota=_ , or _LogsDirectoryQuota=_ must be
               specified.
    
               Added in version 258.
    
           _RuntimeDirectoryPreserve=_
               Takes a boolean argument or **restart**. If set to **no**(the
               default), the directories specified in _RuntimeDirectory=_ are
               always removed when the service stops. If set to **restart** the
               directories are preserved when the service is both
               automatically and manually restarted. Here, the automatic
               restart means the operation specified in _Restart=_ , and manual
               restart means the one triggered by **systemctl restart**
               **foo.service**. If set to **yes** , then the directories are not
               removed when the service is stopped. Note that since the
               runtime directory /run/ is a mount point of "tmpfs", then for
               system services the directories specified in _RuntimeDirectory=_
               are removed when the system is rebooted.
    
               Added in version 235.
    
           _TimeoutCleanSec=_
               Configures a timeout on the clean-up operation requested
               through **systemctl clean ...** , see systemctl(1) for details.
               Takes the usual time values and defaults to **infinity** , i.e. by
               default no timeout is applied. If a timeout is configured the
               clean operation will be aborted forcibly when the timeout is
               reached, potentially leaving resources on disk.
    
               Added in version 244.
    
           _ReadWritePaths=_ , _ReadOnlyPaths=_ , _InaccessiblePaths=_ , _ExecPaths=_ ,
           _NoExecPaths=_
               Sets up a new file system namespace for executed processes.
               These options may be used to limit access a process has to the
               file system. Each setting takes a space-separated list of
               paths relative to the host's root directory (i.e. the system
               running the service manager). Note that if paths contain
               symlinks, they are resolved relative to the root directory set
               with _RootDirectory=_ /_RootImage=_.
    
               Paths listed in _ReadWritePaths=_ are accessible from within the
               namespace with the same access modes as from outside of it.
               Paths listed in _ReadOnlyPaths=_ are accessible for reading
               only, writing will be refused even if the usual file access
               controls would permit this. Nest _ReadWritePaths=_ inside of
               _ReadOnlyPaths=_ in order to provide writable subdirectories
               within read-only directories. Use _ReadWritePaths=_ in order to
               allow-list specific paths for write access if
               _ProtectSystem=strict_ is used. Note that _ReadWritePaths=_ cannot
               be used to gain write access to a file system whose superblock
               is mounted read-only. On Linux, for each mount point write
               access is granted only if the mount point itself _and_ the file
               system superblock backing it are not marked read-only.
               _ReadWritePaths=_ only controls the former, not the latter,
               hence a read-only file system superblock remains protected.
    
               Paths listed in _InaccessiblePaths=_ will be made inaccessible
               for processes inside the namespace along with everything below
               them in the file system hierarchy. This may be more
               restrictive than desired, because it is not possible to nest
               _ReadWritePaths=_ , _ReadOnlyPaths=_ , _BindPaths=_ , or
               _BindReadOnlyPaths=_ inside it. For a more flexible option, see
               _TemporaryFileSystem=_.
    
               Content in paths listed in _NoExecPaths=_ are not executable
               even if the usual file access controls would permit this. Nest
               _ExecPaths=_ inside of _NoExecPaths=_ in order to provide
               executable content within non-executable directories.
    
               Non-directory paths may be specified as well. These options
               may be specified more than once, in which case all paths
               listed will have limited access from within the namespace. If
               the empty string is assigned to this option, the specific list
               is reset, and all prior assignments have no effect.
    
               Paths in _ReadWritePaths=_ , _ReadOnlyPaths=_ , _InaccessiblePaths=_ ,
               _ExecPaths=_ and _NoExecPaths=_ may be prefixed with "-", in which
               case they will be ignored when they do not exist. If prefixed
               with "+" the paths are taken relative to the root directory of
               the unit, as configured with _RootDirectory=_ /_RootImage=_ ,
               instead of relative to the root directory of the host (see
               above). When combining "-" and "+" on the same path make sure
               to specify "-" first, and "+" second.
    
               Note that these settings will disconnect propagation of mounts
               from the unit's processes to the host. This means that this
               setting may not be used for services which shall be able to
               install mount points in the main mount namespace. For
               _ReadWritePaths=_ and _ReadOnlyPaths=_ , propagation in the other
               direction is not affected, i.e. mounts created on the host
               generally appear in the unit processes' namespace, and mounts
               removed on the host also disappear there too. In particular,
               note that mount propagation from host to unit will result in
               unmodified mounts to be created in the unit's namespace, i.e.
               writable mounts appearing on the host will be writable in the
               unit's namespace too, even when propagated below a path marked
               with _ReadOnlyPaths=_! Restricting access with these options
               hence does not extend to submounts of a directory that are
               created later on. This means the lock-down offered by that
               setting is not complete, and does not offer full protection.
    
               Note that the effect of these settings may be undone by
               privileged processes. In order to set up an effective
               sandboxed environment for a unit it is thus recommended to
               combine these settings with either
               _CapabilityBoundingSet=~CAP_SYS_ADMIN_ or
               _SystemCallFilter=~@mount_.
    
               Please be extra careful when applying these options to API
               file systems (a list of them could be found in _MountAPIVPS=_),
               since they may be required for basic system functionalities.
               Moreover, /run/ needs to be writable for setting up mount
               namespace and propagation.
    
               Simple allow-list example using these directives:
    
                   [Service]
                   ReadOnlyPaths=/
                   ReadWritePaths=/var /run
                   InaccessiblePaths=-/lost+found
                   NoExecPaths=/
                   ExecPaths=/usr/sbin/my_daemon /usr/lib /usr/lib64
    
               These options are only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 231.
    
           _TemporaryFileSystem=_
               Takes a space-separated list of mount points for temporary
               file systems (tmpfs). If set, a new file system namespace is
               set up for executed processes, and a temporary file system is
               mounted on each mount point. This option may be specified more
               than once, in which case temporary file systems are mounted on
               all listed mount points. If the empty string is assigned to
               this option, the list is reset, and all prior assignments have
               no effect. Each mount point may optionally be suffixed with a
               colon (":") and mount options such as "size=10%" or "ro". By
               default, each temporary file system is mounted with
               "nodev,strictatime,mode=0755". These can be disabled by
               explicitly specifying the corresponding mount options, e.g.,
               "dev" or "nostrictatime".
    
               This is useful to hide files or directories not relevant to
               the processes invoked by the unit, while necessary files or
               directories can be still accessed by combining with _BindPaths=_
               or _BindReadOnlyPaths=_ :
    
               Example: if a unit has the following,
    
                   TemporaryFileSystem=/var:ro
                   BindReadOnlyPaths=/var/lib/systemd
    
               then the invoked processes by the unit cannot see any files or
               directories under /var/ except for /var/lib/systemd or its
               contents.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 238.
    
           _PrivateTmp=_
               Takes a boolean argument, or "disconnected". If enabled, a new
               file system namespace will be set up for the executed
               processes, and /tmp/ and /var/tmp/ directories inside it are
               not shared with processes outside of the namespace, plus all
               temporary files created by a service in these directories will
               be removed after the service is stopped. For this setting, the
               same restrictions regarding mount propagation and privileges
               apply as for _ReadOnlyPaths=_ and related calls, see above. This
               setting is useful to secure access to temporary files of the
               process, but makes sharing between processes via /tmp/ or
               /var/tmp/ impossible. If _DynamicUser=_ is enabled,
               "disconnected" is implied. Otherwise, defaults to false.
    
               If "true", the backing storage of the private temporary
               directories will remain on the host's /tmp/ and /var/tmp/
               directories. It is possible to run two or more units within
               the same private /tmp/ and /var/tmp/ namespace by using the
               _JoinsNamespaceOf=_ directive, see systemd.unit(5) for details.
               This has the side effect of adding _Wants=_ and _After=_
               dependencies on all mount units necessary to access /tmp/ and
               /var/tmp/ on the host. Moreover, an implicit _After=_ ordering
               on systemd-tmpfiles-setup.service(8) is added.
    
               If "disconnected", the directories will be backed by a
               completely new tmpfs instance, meaning that the storage is
               fully disconnected from the host namespace. The tmpfs instance
               does not shared with other units even if the _JoinsNamespaceOf=_
               directive is used. If _DefaultDependencies=no_ is specified,
               _RequiresMountsFor=/WantsMountsFor=_ for /var/ is not specified,
               and _RootDirectory=/RootImage=_ is not specified, then a new
               tmpfs is mounted _only_ on /tmp/, hence the host's /var/tmp is
               still accessible from the unit. In that case, _$TMPDIR_
               environment variable is set to "/tmp" to suggest the processes
               in the unit to use /tmp/. This automatically adds
               _WantsMountsFor=/var/_ dependency, unless _DefaultDependencies=no_
               and/or _RootDirectory=/RootImage=_ are specified.
    
               **Table 3. Summary for** _PrivateTmp=disconnected_
               ┌───────────────────────────┬───────────┬──────────────┬──────────────────────┐
               │ **Other Settings** │ **tmpfs on** │ **$TMPVAR** │ **implied** │
               │                           │ **/var/tmp/** │              │ **dependencies** │
               ├───────────────────────────┼───────────┼──────────────┼──────────────────────┤
               │ (none)                    │ yes       │ (unset)      │ _WantsMountsFor=/var/_ │
               ├───────────────────────────┼───────────┼──────────────┼──────────────────────┤
               │ _RootDirectory=/RootImage=_ │ yes       │ (unset)      │ (none)               │
               ├───────────────────────────┼───────────┼──────────────┼──────────────────────┤
               │ _DefaultDependency=no_ ,     │ yes       │ (unset)      │ (none)               │
               │ _RequiresMountsFor=/var/_   │           │              │                      │
               ├───────────────────────────┼───────────┼──────────────┼──────────────────────┤
               │ _DefaultDependency=no_ ,     │ yes       │ (unset)      │ (none)               │
               │ _WantsMountsFor=/var/_      │           │              │                      │
               ├───────────────────────────┼───────────┼──────────────┼──────────────────────┤
               │ _DefaultDependency=no_      │ no        │ _$TMPDIR=/tmp_ │ (none)               │
               └───────────────────────────┴───────────┴──────────────┴──────────────────────┘
    
               Note that the implementation of this setting might be
               impossible (for example if mount namespaces are not
               available), and the unit should be written in a way that does
               not solely rely on this setting for security.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
           _PrivateDevices=_
               Takes a boolean argument. If true, sets up a new /dev/ mount
               for the executed processes and only adds API pseudo devices
               such as /dev/null, /dev/zero or /dev/random (as well as the
               pseudo TTY subsystem) to it, but no physical devices such as
               /dev/sda, system memory /dev/mem, system ports /dev/port and
               others. This is useful to turn off physical device access by
               the executed process. Defaults to false.
    
               Enabling this option will install a system call filter to
               block low-level I/O system calls that are grouped in the
               _@raw-io_ set, remove **CAP_MKNOD** and **CAP_SYS_RAWIO** from the
               capability bounding set for the unit, and set
               _DevicePolicy=closed_ (see systemd.resource-control(5) for
               details). Note that using this setting will disconnect
               propagation of mounts from the service to the host
               (propagation in the opposite direction continues to work).
               This means that this setting may not be used for services
               which shall be able to install mount points in the main mount
               namespace. The new /dev/ will be mounted read-only and
               'noexec'. The latter may break old programs which try to set
               up executable memory by using mmap(2) of /dev/zero instead of
               using **MAP_ANON**. For this setting the same restrictions
               regarding mount propagation and privileges apply as for
               _ReadOnlyPaths=_ and related calls, see above.
    
               Note that the implementation of this setting might be
               impossible (for example if mount namespaces are not
               available), and the unit should be written in a way that does
               not solely rely on this setting for security.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               When access to some but not all devices must be possible, the
               _DeviceAllow=_ setting might be used instead. See
               systemd.resource-control(5).
    
               Added in version 209.
    
           _PrivateNetwork=_
               Takes a boolean argument. If true, sets up a new network
               namespace for the executed processes and configures only the
               loopback network device "lo" inside it. No other network
               devices will be available to the executed process. This is
               useful to turn off network access by the executed process.
               Defaults to false. It is possible to run two or more units
               within the same private network namespace by using the
               _JoinsNamespaceOf=_ directive, see systemd.unit(5) for details.
               Note that this option will disconnect all socket families from
               the host, including **AF_NETLINK** and **AF_UNIX**. Effectively, for
               **AF_NETLINK** this means that device configuration events
               received from systemd-udevd.service(8) are not delivered to
               the unit's processes. And for **AF_UNIX** this has the effect that
               **AF_UNIX** sockets in the abstract socket namespace of the host
               will become unavailable to the unit's processes (however,
               those located in the file system will continue to be
               accessible).
    
               Note that the implementation of this setting might be
               impossible (for example if network namespaces are not
               available), and the unit should be written in a way that does
               not solely rely on this setting for security.
    
               When this option is enabled, _PrivateMounts=_ is implied unless
               it is explicitly disabled, and /sys will be remounted to
               associate it with the new network namespace.
    
               When this option is used on a socket unit any sockets bound on
               behalf of this unit will be bound within a private network
               namespace. This may be combined with _JoinsNamespaceOf=_ to
               listen on sockets inside of network namespaces of other
               services.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
           _NetworkNamespacePath=_
               Takes an absolute file system path referring to a Linux
               network namespace pseudo-file (i.e. a file like
               /proc/$PID/ns/net or a bind mount or symlink to one). When set
               the invoked processes are added to the network namespace
               referenced by that path. The path has to point to a valid
               namespace file at the moment the processes are forked off. If
               this option is used _PrivateNetwork=_ has no effect. If this
               option is used together with _JoinsNamespaceOf=_ then it only
               has an effect if this unit is started before any of the listed
               units that have _PrivateNetwork=_ or _NetworkNamespacePath=_
               configured, as otherwise the network namespace of those units
               is reused.
    
               When this option is enabled, _PrivateMounts=_ is implied unless
               it is explicitly disabled, and /sys will be remounted to
               associate it with the new network namespace.
    
               When this option is used on a socket unit any sockets bound on
               behalf of this unit will be bound within the specified network
               namespace.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 242.
    
           _PrivateIPC=_
               Takes a boolean argument. If true, sets up a new IPC namespace
               for the executed processes. Each IPC namespace has its own set
               of System V IPC identifiers and its own POSIX message queue
               file system. This is useful to avoid name clash of IPC
               identifiers. Defaults to false. It is possible to run two or
               more units within the same private IPC namespace by using the
               _JoinsNamespaceOf=_ directive, see systemd.unit(5) for details.
    
               Note that IPC namespacing does not have an effect on **AF_UNIX**
               sockets, which are the most common form of IPC used on Linux.
               Instead, **AF_UNIX** sockets in the file system are subject to
               mount namespacing, and those in the abstract namespace are
               subject to network namespacing. IPC namespacing only has an
               effect on SysV IPC (which is mostly legacy) as well as POSIX
               message queues (for which **AF_UNIX** /**SOCK_SEQPACKET** sockets are
               typically a better replacement). IPC namespacing also has no
               effect on POSIX shared memory (which is subject to mount
               namespacing) either. See ipc_namespaces(7) for the details.
    
               Note that the implementation of this setting might be
               impossible (for example if IPC namespaces are not available),
               and the unit should be written in a way that does not solely
               rely on this setting for security.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 248.
    
           _IPCNamespacePath=_
               Takes an absolute file system path referring to a Linux IPC
               namespace pseudo-file (i.e. a file like /proc/$PID/ns/ipc or a
               bind mount or symlink to one). When set the invoked processes
               are added to the network namespace referenced by that path.
               The path has to point to a valid namespace file at the moment
               the processes are forked off. If this option is used
               _PrivateIPC=_ has no effect. If this option is used together
               with _JoinsNamespaceOf=_ then it only has an effect if this unit
               is started before any of the listed units that have
               _PrivateIPC=_ or _IPCNamespacePath=_ configured, as otherwise the
               network namespace of those units is reused.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 248.
    
           _MemoryKSM=_
               Takes a boolean argument. When set, it enables KSM (kernel
               samepage merging) for the processes. KSM is a memory-saving
               de-duplication feature. Anonymous memory pages with identical
               content can be replaced by a single write-protected page. This
               feature should only be enabled for jobs that share the same
               security domain. For details, see **Kernel Samepage Merging******[12]
               in the kernel documentation.
    
               Note that this functionality might not be available, for
               example if KSM is disabled in the kernel, or the kernel does
               not support controlling KSM at the process level throughprctl(2).
    
               Added in version 254.
    
           _PrivatePIDs=_
               Takes a boolean argument. Defaults to false. If enabled, sets
               up a new PID namespace for the executed processes. Each
               executed process is now PID 1 - the init process - in the new
               namespace.  /proc/ is mounted such that only processes in the
               PID namespace are visible. If _PrivatePIDs=_ is set,
               _MountAPIVFS=yes_ is implied.
    
               _PrivatePIDs=_ is only supported for service units. This setting
               is not supported with _Type=forking_ since the kernel will kill
               all processes in the PID namespace if the init process
               terminates.
    
               This setting will be ignored if the kernel does not support
               PID namespaces.
    
               Note unprivileged user services (i.e. a service run by the
               per-user instance of the service manager) will fail with
               _PrivatePIDs=yes_ if /proc/ is masked (i.e.  /proc/kmsg is
               over-mounted with **tmpfs** like systemd-nspawn(1) does). This is
               due to a kernel restriction not allowing unprivileged user
               namespaces to mount a less restrictive instance of /proc/.
    
               Added in version 257.
    
           _PrivateUsers=_
               Takes a boolean argument or one of "self", "identity", or
               "full". Defaults to false. If enabled, sets up a new user
               namespace for the executed processes and configures a user and
               group mapping. If set to a true value or "self", a minimal
               user and group mapping is configured that maps the "root" user
               and group as well as the unit's own user and group to
               themselves and everything else to the "nobody" user and group.
               This is useful to securely detach the user and group databases
               used by the unit from the rest of the system, and thus to
               create an effective sandbox environment. All files,
               directories, processes, IPC objects and other resources owned
               by users/groups not equaling "root" or the unit's own will
               stay visible from within the unit but appear owned by the
               "nobody" user and group.
    
               If the parameter is "identity", user namespacing is set up
               with an identity mapping for the first 65536 UIDs/GIDs. Any
               UIDs/GIDs above 65536 will be mapped to the "nobody" user and
               group, respectively. While this does not provide UID/GID
               isolation, since all UIDs/GIDs are chosen identically it does
               provide process capability isolation, and hence is often a
               good choice if proper user namespacing with distinct UID maps
               is not appropriate.
    
               If the parameter is "full", user namespacing is set up with an
               identity mapping for all UIDs/GIDs. In addition, for system
               services, "full" allows the unit to call **setgroups()** system
               calls (by setting /proc/_pid_ /setgroups to "allow"). Similar to
               "identity", this does not provide UID/GID isolation, but it
               does provide process capability isolation.
    
               If this mode is enabled, all unit processes are run without
               privileges in the host user namespace (regardless of whether
               the unit's own user/group is "root" or not). Specifically this
               means that the process will have zero process capabilities on
               the host's user namespace, but full capabilities within the
               service's user namespace. Settings such as
               _CapabilityBoundingSet=_ will affect only the latter, and
               there's no way to acquire additional capabilities in the
               host's user namespace.
    
               When this setting is set up by a per-user instance of the
               service manager, the mapping of the "root" user and group to
               itself is omitted (unless the user manager is root).
               Additionally, in the per-user instance manager case, the user
               namespace will be set up before most other namespaces. This
               means that combining _PrivateUsers=_**true** with other namespaces
               will enable use of features not normally supported by the
               per-user instances of the service manager.
    
               This setting is particularly useful in conjunction with
               _RootDirectory=_ /_RootImage=_ , as the need to synchronize the user
               and group databases in the root directory and on the host is
               reduced, as the only users and groups who need to be matched
               are "root", "nobody" and the unit's own user and group.
    
               Added in version 232.
    
           _ProtectHostname=_
               Takes a boolean argument or "private". If enabled, sets up a
               new UTS namespace for the executed processes. If enabled, a
               hostname can be optionally specified following a colon (e.g.
               "yes:foo" or "private:host.example.com"), and the hostname is
               set in the new UTS namespace for the unit. If set to a true
               value, changing hostname or domainname via **sethostname()** and
               **setdomainname()** system calls is prevented. If set to
               "private", changing hostname or domainname is allowed but only
               affects the unit's UTS namespace. Defaults to off.
    
               Note that the implementation of this setting might be
               impossible (for example if UTS namespaces are not available),
               and the unit should be written in a way that does not solely
               rely on this setting for security.
    
               Note that when this option is enabled for a service hostname
               changes no longer propagate from the system into the service,
               it is hence not suitable for services that need to take notice
               of system hostname changes dynamically.
    
               Note that this option does not prevent changing system
               hostname via **hostnamectl**. However, _User=_ and _Group=_ may be
               used to run as an unprivileged user to disallow changing
               system hostname. See **SetHostname()** in
               org.freedesktop.hostname1(5) for more details.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 242.
    
           _ProtectClock=_
               Takes a boolean argument. If set, writes to the hardware clock
               or system clock will be denied. Defaults to off. Enabling this
               option removes **CAP_SYS_TIME** and **CAP_WAKE_ALARM** from the
               capability bounding set for this unit, installs a system call
               filter to block calls that can set the clock, and
               _DeviceAllow=char-rtc r_ is implied. Note that the system calls
               are blocked altogether, the filter does not take into account
               that some of the calls can be used to read the clock state
               with some parameter combinations. Effectively, /dev/rtc0,
               /dev/rtc1, etc. are made read-only to the service. See
               systemd.resource-control(5) for the details about
               _DeviceAllow=_.
    
               It is recommended to turn this on for most services that do
               not need modify the clock or check its state.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 245.
    
           _ProtectKernelTunables=_
               Takes a boolean argument. If true, kernel variables accessible
               through /proc/sys/, /sys/, /proc/sysrq-trigger,
               /proc/latency_stats, /proc/acpi, /proc/timer_stats, /proc/fs
               and /proc/irq will be made read-only and /proc/kallsyms as
               well as /proc/kcore will be inaccessible to all processes of
               the unit. Usually, tunable kernel variables should be
               initialized only at boot-time, for example with the
               sysctl.d(5) mechanism. Few services need to write to these at
               runtime; it is hence recommended to turn this on for most
               services. For this setting the same restrictions regarding
               mount propagation and privileges apply as for _ReadOnlyPaths=_
               and related calls, see above. Defaults to off. Note that this
               option does not prevent indirect changes to kernel tunables
               affected by IPC calls to other processes. However,
               _InaccessiblePaths=_ may be used to make relevant IPC file
               system objects inaccessible. If _ProtectKernelTunables=_ is set,
               _MountAPIVFS=yes_ is implied.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 232.
    
           _ProtectKernelModules=_
               Takes a boolean argument. If true, explicit module loading
               will be denied. This allows module load and unload operations
               to be turned off on modular kernels. It is recommended to turn
               this on for most services that do not need special file
               systems or extra kernel modules to work. Defaults to off.
               Enabling this option removes **CAP_SYS_MODULE** from the
               capability bounding set for the unit, and installs a system
               call filter to block module system calls, also
               /usr/lib/modules is made inaccessible. For this setting the
               same restrictions regarding mount propagation and privileges
               apply as for _ReadOnlyPaths=_ and related calls, see above. Note
               that limited automatic module loading due to user
               configuration or kernel mapping tables might still happen as
               side effect of requested user operations, both privileged and
               unprivileged. To disable module auto-load feature please see
               sysctl.d(5) **kernel.modules_disabled** mechanism and
               /proc/sys/kernel/modules_disabled documentation.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 232.
    
           _ProtectKernelLogs=_
               Takes a boolean argument. If true, access to the kernel log
               ring buffer will be denied. It is recommended to turn this on
               for most services that do not need to read from or write to
               the kernel log ring buffer. Enabling this option removes
               **CAP_SYSLOG** from the capability bounding set for this unit, and
               installs a system call filter to block the syslog(2) system
               call (not to be confused with the libc API syslog(3) for
               userspace logging). The kernel exposes its log buffer to
               userspace via /dev/kmsg and /proc/kmsg. If enabled, these are
               made inaccessible to all the processes in the unit.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 244.
    
           _ProtectControlGroups=_
               Takes a boolean argument or the special values "private" or
               "strict". If true, the Linux Control Groups (cgroups(7))
               hierarchies accessible through /sys/fs/cgroup/ will be made
               read-only to all processes of the unit. If set to "private",
               the unit will run in a cgroup namespace with a private
               writable mount of /sys/fs/cgroup/. If set to "strict", the
               unit will run in a cgroup namespace with a private read-only
               mount of /sys/fs/cgroup/. Defaults to off. If
               _ProtectControlGroups=_ is set, _MountAPIVFS=yes_ is implied. Note
               "private" and "strict" are downgraded to false and true
               respectively unless the system is using the unified control
               group hierarchy and the kernel supports cgroup namespaces.
    
               Except for container managers no services should require write
               access to the control groups hierarchies; it is hence
               recommended to set _ProtectControlGroups=_ to true or "strict"
               for most services. For this setting the same restrictions
               regarding mount propagation and privileges apply as for
               _ReadOnlyPaths=_ and related settings, see above.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 232.
    
           _RestrictAddressFamilies=_
               Restricts the set of socket address families accessible to the
               processes of this unit. Takes "none", or a space-separated
               list of address family names to allow-list, such as **AF_UNIX** ,
               **AF_INET** or **AF_INET6** , see address_families(7) for all possible
               options. When "none" is specified, then all address families
               will be denied. When prefixed with "~" the listed address
               families will be applied as deny list, otherwise as allow
               list.
    
               By default, no restrictions apply, all address families are
               accessible to processes. If assigned the empty string, any
               previous address family restriction changes are undone. This
               setting does not affect commands prefixed with "+".
    
               Use this option to limit exposure of processes to remote
               access, in particular via exotic and sensitive network
               protocols, such as **AF_PACKET**. Note that in most cases, the
               local **AF_UNIX** address family should be included in the
               configured allow list as it is frequently used for local
               communication, including for syslog(2) logging.
    
               Note that this restricts access to the socket(2) system call
               only. Sockets passed into the process by other means (for
               example, by using socket activation with socket units, see
               systemd.socket(5)) are unaffected. Also, sockets created with
               **socketpair()**(which creates connected AF_UNIX sockets) or the
               io_uring(7) functions, are not affected. Thus, it is
               recommended to combined this setting with
               _SystemCallFilter=@service_ , to only allow a limited subset of
               system calls.
    
               Note that this option is limited to some ABIs, in particular
               x86-64, but currently has no effect on 32-bit x86, s390,
               s390x, mips, mips-le, ppc, ppc-le, ppc64, or ppc64-le, and is
               ignored. On systems supporting multiple ABIs (such as
               x86/x86-64) it is recommended to turn off alternative ABIs for
               services, so that they cannot be used to circumvent the
               restrictions of this option. Specifically, it is recommended
               to combine this option with _SystemCallArchitectures=native_ or
               similar.
    
               Added in version 211.
    
           _RestrictFileSystems=_
               Restricts the set of filesystems processes of this unit can
               open files on. Takes a space-separated list of filesystem
               names. Any filesystem listed is made accessible to the unit's
               processes, access to filesystem types not listed is prohibited
               (allow-listing). If the first character of the list is "~",
               the effect is inverted: access to the filesystems listed is
               prohibited (deny-listing). If the empty string is assigned,
               access to filesystems is not restricted.
    
               If you specify both types of this option (i.e. allow-listing
               and deny-listing), the first encountered will take precedence
               and will dictate the default action (allow access to the
               filesystem or deny it). Then the next occurrences of this
               option will add or delete the listed filesystems from the set
               of the restricted filesystems, depending on its type and the
               default action.
    
               Example: if a unit has the following,
    
                   RestrictFileSystems=ext4 tmpfs
                   RestrictFileSystems=ext2 ext4
    
               then access to **ext4** , **tmpfs** , and **ext2** is allowed and access to
               other filesystems is denied.
    
               Example: if a unit has the following,
    
                   RestrictFileSystems=ext4 tmpfs
                   RestrictFileSystems=~ext4
    
               then only access **tmpfs** is allowed.
    
               Example: if a unit has the following,
    
                   RestrictFileSystems=~ext4 tmpfs
                   RestrictFileSystems=ext4
    
               then only access to **tmpfs** is denied.
    
               As the number of possible filesystems is large, predefined
               sets of filesystems are provided. A set starts with "@"
               character, followed by name of the set.
    
               **Table 4. Currently predefined filesystem sets**
               ┌───────────────────┬──────────────────────────┐
               │ **Set** │ **Description** │
               ├───────────────────┼──────────────────────────┤
               │ @basic-api        │ Basic filesystem API.    │
               ├───────────────────┼──────────────────────────┤
               │ @auxiliary-api    │ Auxiliary filesystem     │
               │                   │ API.                     │
               ├───────────────────┼──────────────────────────┤
               │ @common-block     │ Common block device      │
               │                   │ filesystems.             │
               ├───────────────────┼──────────────────────────┤
               │ @historical-block │ Historical block device  │
               │                   │ filesystems.             │
               ├───────────────────┼──────────────────────────┤
               │ @network          │ Well-known network       │
               │                   │ filesystems.             │
               ├───────────────────┼──────────────────────────┤
               │ @privileged-api   │ Privileged filesystem    │
               │                   │ API.                     │
               ├───────────────────┼──────────────────────────┤
               │ @temporary        │ Temporary filesystems:   │
               │                   │ tmpfs, ramfs.            │
               ├───────────────────┼──────────────────────────┤
               │ @known            │ All known filesystems    │
               │                   │ defined by the kernel.   │
               │                   │ This list is defined     │
               │                   │ statically in systemd    │
               │                   │ based on a kernel        │
               │                   │ version that was         │
               │                   │ available when this      │
               │                   │ systemd version was      │
               │                   │ released. It will become │
               │                   │ progressively more       │
               │                   │ out-of-date as the       │
               │                   │ kernel is updated.       │
               └───────────────────┴──────────────────────────┘
    
               Use systemd-analyze(1)'s **filesystems** command to retrieve a
               list of filesystems defined on the local system.
    
               Note that this setting might not be supported on some systems
               (for example if the LSM eBPF hook is not enabled in the
               underlying kernel or if not using the unified control group
               hierarchy). In that case this setting has no effect.
    
               This option cannot be bypassed by prefixing "+" to the
               executable path in the service unit, as it applies to the
               whole control group.
    
               Added in version 250.
    
           _RestrictNamespaces=_
               Restricts access to Linux namespace functionality for the
               processes of this unit. For details about Linux namespaces,
               see namespaces(7). Either takes a boolean argument, or a
               space-separated list of namespace type identifiers. If false
               (the default), no restrictions on namespace creation and
               switching are made. If true, access to any kind of namespacing
               is prohibited. Otherwise, a space-separated list of namespace
               type identifiers must be specified, consisting of any
               combination of: **cgroup** , **ipc** , **net** , **mnt** , **pid** , **user** , **uts** , and
               **time**. Any namespace type listed is made accessible to the
               unit's processes, access to namespace types not listed is
               prohibited (allow-listing). By prepending the list with a
               single tilde character ("~") the effect may be inverted: only
               the listed namespace types will be made inaccessible, all
               unlisted ones are permitted (deny-listing). If the empty
               string is assigned, the default namespace restrictions are
               applied, which is equivalent to false. This option may appear
               more than once, in which case the namespace types are merged
               by **OR** , or by **AND** if the lines are prefixed with "~" (see
               examples below). Internally, this setting limits access to the
               unshare(2), clone(2) and setns(2) system calls, taking the
               specified flags parameters into account. Note that — if this
               option is used — in addition to restricting creation and
               switching of the specified types of namespaces (or all of
               them, if true) access to the **setns()** system call with a zero
               flags parameter is prohibited. This setting is only supported
               on x86, x86-64, mips, mips-le, mips64, mips64-le, mips64-n32,
               mips64-le-n32, ppc64, ppc64-le, s390 and s390x, and enforces
               no restrictions on other architectures.
    
               Example: if a unit has the following,
    
                   RestrictNamespaces=cgroup ipc
                   RestrictNamespaces=cgroup net
    
               then **cgroup** , **ipc** , and **net** are set. If the second line is
               prefixed with "~", e.g.,
    
                   RestrictNamespaces=cgroup ipc
                   RestrictNamespaces=~cgroup net
    
               then, only **ipc** is set.
    
               Added in version 233.
    
           _DelegateNamespaces=_
               Delegates ownership of the given namespace types to the user
               namespace of the processes of this unit. For details about
               Linux namespaces, see namespaces(7). Either takes a boolean
               argument, or a space-separated list of namespace type
               identifiers. If false (the default), the unit's processes'
               user namespace will not have ownership over any namespaces
               created during setup of the unit's sandboxed environment. If
               true, ownership of all namespace types (except for user
               namespaces, where the concept doesn't apply) created during
               setup of the unit's sandboxed environment is delegated to the
               unit's processes' user namespace. Otherwise, a space-separated
               list of namespace type identifiers must be specified,
               consisting of any combination of: **cgroup** , **ipc** , **net** , **mnt** , **pid** ,
               and **uts**. All namespaces of the listed types will be owned by
               the unit's processes' user namespace if they are created
               during setup of the unit's sandboxed environment
               (allow-listing). By prepending the list with a single tilde
               character ("~") the effect may be inverted: all namespaces of
               types not listed and created during setup of the unit's
               sandboxed environment will be owned by the unit's processes'
               user namespace (deny-listing). If the empty string is
               assigned, the default namespace ownership is applied, which is
               equivalent to false. This option may appear more than once, in
               which case the namespace types are merged by **OR** , or by **AND** if
               the lines are prefixed with "~" (see examples below).
               Internally, this setting controls the order in which
               namespaces are unshared by systemd. Namespace types that
               should be owned by the unit's processes' user namespace will
               be unshared after unsharing the user namespace. Internally,
               this setting controls the order in which namespaces are
               unshared. Delegated namespaces will be unshared after the user
               namespace is unshared. Other namespaces will be unshared
               before the user namespace is unshared.
    
               Delegating any namespace with _DelegateNamespaces=_ implies
               _PrivateUsers=self_ unless _PrivateUsers=_ is explicitly enabled
               already by the unit. Delegating a namespace does not imply
               that the namespace is unshared, that is done with the
               namespace specific unit setting such as _PrivateNetwork=_ or
               _PrivateMounts=_.
    
               Note that some namespace sandboxing options might entail mount
               namespace for private API VFS instances, such as _PrivatePIDs=_ ,
               _ProtectControlGroups=private/strict_ , or _PrivateNetwork=_. If
               any of the mentioned options are enabled, mount namespace is
               implicitly delegated.
    
               Added in version 258.
    
           _PrivateBPF=_
               Takes a boolean argument. If set, mount a private instance of
               the BPF filesystem on /sys/fs/bpf/, effectively hiding the
               host bpffs which contains information about loaded programs
               and maps. Otherwise, if _ProtectKernelTunables=_ is set, the
               instance from the host is inherited but mounted read-only.
               Defaults to false.
    
               This can be used together with the bpffs delegate feature to
               choose what BPF functions are available to the unit's
               processes. When mounting the BPF filesystem with the fsopen()
               API, four mount options can be specified to set a list of BPF
               commands, maps, programs and attachment types that are allowed
               to be used. Processes needs to get a file descriptor for the
               bpffs mountpoint and use that to get a token which will enable
               for that user namespace the BPF functionalities chosen upon
               bpffs mount. A more detailed explanation of the feature can be
               found in this **LWN post******[13].
    
               Added in version 258._BPFDelegateCommands=_
               Accepts a list of BPF commands to allow or "any" to allow
               everything. Defaults to none. The accepted values are:
               **BPFMapCreate BPFMapLookupElem BPFMapUpdateElem**
               **BPFMapDeleteElem BPFMapGetNextKey BPFProgLoad BPFObjPin**
               **BPFObjGet BPFProgAttach BPFProgDetach BPFProgTestRun**
               **BPFProgGetNextId BPFMapGetNextId BPFProgGetFdById**
               **BPFMapGetFdById BPFObjGetInfoByFd BPFProgQuery**
               **BPFRawTracepointOpen BPFBtfLoad BPFBtfGetFdById BPFTaskFdQuery**
               **BPFMapLookupAndDeleteElem BPFMapFreeze BPFBtfGetNextId**
               **BPFMapLookupBatch BPFMapLookupAndDeleteBatch BPFMapUpdateBatch**
               **BPFMapDeleteBatch BPFLinkCreate BPFLinkUpdate BPFLinkGetFdById**
               **BPFLinkGetNextId BPFEnableStats BPFIterCreate BPFLinkDetach**
               **BPFProgBindMap BPFTokenCreate** This will set the **delegate_cmds**
               bpffs mount option.
    
               Requires _PrivateBPF=yes_ to be effective, see _PrivateBPF=_ more
               details.
    
               Added in version 258.
    
           _BPFDelegateMaps=_
               Accepts a list of BPF maps to allow or "any" to allow
               everything. Defaults to none. The accepted values are:
               **BPFMapTypeUnspec BPFMapTypeHash BPFMapTypeArray**
               **BPFMapTypeProgArray BPFMapTypePerfEventArray**
               **BPFMapTypePercpuHash BPFMapTypePercpuArray**
               **BPFMapTypeStackTrace BPFMapTypeCgroupArray BPFMapTypeLruHash**
               **BPFMapTypeLruPercpuHash BPFMapTypeLpmTrie**
               **BPFMapTypeArrayOfMaps BPFMapTypeHashOfMaps BPFMapTypeDevmap**
               **BPFMapTypeSockmap BPFMapTypeCpumap BPFMapTypeXskmap**
               **BPFMapTypeSockhash BPFMapTypeCgroupStorageDeprecated**
               **BPFMapTypeReuseportSockarray**
               **BPFMapTypePercpuCgroupStorageDeprecated BPFMapTypeQueue**
               **BPFMapTypeStack BPFMapTypeSkStorage BPFMapTypeDevmapHash**
               **BPFMapTypeStructOps BPFMapTypeRingbuf BPFMapTypeInodeStorage**
               **BPFMapTypeTaskStorage BPFMapTypeBloomFilter**
               **BPFMapTypeUserRingbuf BPFMapTypeCgrpStorage BPFMapTypeArena**
               This will set the **delegate_maps** bpffs mount option.
    
               Requires _PrivateBPF=yes_ to be effective, see _PrivateBPF=_ more
               details.
    
               Added in version 258.
    
           _BPFDelegatePrograms=_
               Accepts a list of BPF programs to allow or "any" to allow
               everything. Defaults to none. The accepted values are:
               **BPFProgTypeUnspec BPFProgTypeSocketFilter BPFProgTypeKprobe**
               **BPFProgTypeSchedCls BPFProgTypeSchedAct BPFProgTypeTracepoint**
               **BPFProgTypeXdp BPFProgTypePerfEvent BPFProgTypeCgroupSkb**
               **BPFProgTypeCgroupSock BPFProgTypeLwtIn BPFProgTypeLwtOut**
               **BPFProgTypeLwtXmit BPFProgTypeSockOps BPFProgTypeSkSkb**
               **BPFProgTypeCgroupDevice BPFProgTypeSkMsg**
               **BPFProgTypeRawTracepoint BPFProgTypeCgroupSockAddr**
               **BPFProgTypeLwtSeg6local BPFProgTypeLircMode2**
               **BPFProgTypeSkReuseport BPFProgTypeFlowDissector**
               **BPFProgTypeCgroupSysctl BPFProgTypeRawTracepointWritable**
               **BPFProgTypeCgroupSockopt BPFProgTypeTracing**
               **BPFProgTypeStructOps BPFProgTypeExt BPFProgTypeLsm**
               **BPFProgTypeSkLookup BPFProgTypeNetfilter** This will set the
               **delegate_progs** bpffs mount option.
    
               Requires _PrivateBPF=yes_ to be effective, see _PrivateBPF=_ more
               details.
    
               Added in version 258.
    
           _BPFDelegateAttachments=_
               Accepts a list of BPF attach points to allow or "any" to allow
               everything. Defaults to none. The accepted values are:
               **BPFCgroupInetIngress BPFCgroupInetEgress**
               **BPFCgroupInetSockCreate BPFCgroupSockOps BPFSkSkbStreamParser**
               **BPFSkSkbStreamVerdict BPFCgroupDevice BPFSkMsgVerdict**
               **BPFCgroupInet4Bind BPFCgroupInet6Bind BPFCgroupInet4Connect**
               **BPFCgroupInet6Connect BPFCgroupInet4PostBind**
               **BPFCgroupInet6PostBind BPFCgroupUdp4Sendmsg**
               **BPFCgroupUdp6Sendmsg BPFLircMode2 BPFFlowDissector**
               **BPFCgroupSysctl BPFCgroupUdp4Recvmsg BPFCgroupUdp6Recvmsg**
               **BPFCgroupGetsockopt BPFCgroupSetsockopt BPFTraceRawTp**
               **BPFTraceFentry BPFTraceFexit BPFModifyReturn BPFLsmMac**
               **BPFTraceIter BPFCgroupInet4Getpeername**
               **BPFCgroupInet6Getpeername BPFCgroupInet4Getsockname**
               **BPFCgroupInet6Getsockname BPFXdpDevmap**
               **BPFCgroupInetSockRelease BPFXdpCpumap BPFSkLookup BPFXdp**
               **BPFSkSkbVerdict BPFSkReuseportSelect**
               **BPFSkReuseportSelectOrMigrate BPFPerfEvent BPFTraceKprobeMulti**
               **BPFLsmCgroup BPFStructOps BPFNetfilter BPFTcxIngress**
               **BPFTcxEgress BPFTraceUprobeMulti BPFCgroupUnixConnect**
               **BPFCgroupUnixSendmsg BPFCgroupUnixRecvmsg**
               **BPFCgroupUnixGetpeername BPFCgroupUnixGetsockname**
               **BPFNetkitPrimary BPFNetkitPeer BPFTraceKprobeSession**
               **BPFTraceUprobeSession** This will set the **delegate_attachs** bpffs
               mount option.
    
               Requires _PrivateBPF=yes_ to be effective, see _PrivateBPF=_ more
               details.
    
               Added in version 258.
    
           _LockPersonality=_
               Takes a boolean argument. If set, locks down the
               personality(2) system call so that the kernel execution domain
               may not be changed from the default or the personality
               selected with _Personality=_ directive. This may be useful to
               improve security, because odd personality emulations may be
               poorly tested and source of vulnerabilities.
    
               Added in version 235.
    
           _MemoryDenyWriteExecute=_
               Takes a boolean argument. If set, attempts to create memory
               mappings that are writable and executable at the same time, or
               to change existing memory mappings to become executable, or
               mapping shared memory segments as executable, are prohibited.
               Specifically, a system call filter is added (or preferably, an
               equivalent kernel check is enabled with prctl(2)) that rejects
               mmap(2) system calls with both **PROT_EXEC** and **PROT_WRITE** set,
               mprotect(2) or pkey_mprotect(2) system calls with **PROT_EXEC**
               set and shmat(2) system calls with **SHM_EXEC** set. Note that
               this option is incompatible with programs and libraries that
               generate program code dynamically at runtime, including JIT
               execution engines, executable stacks, and code "trampoline"
               feature of various C compilers. This option improves service
               security, as it makes harder for software exploits to change
               running code dynamically. However, the protection can be
               circumvented, if the service can write to a filesystem, which
               is not mounted with **noexec**(such as /dev/shm), or it can use
               **memfd_create()**. This can be prevented by making such file
               systems inaccessible to the service (e.g.
               _InaccessiblePaths=/dev/shm_) and installing further system call
               filters (_SystemCallFilter=~memfd_create_). Note that this
               feature is fully available on x86-64, and partially on x86.
               Specifically, the **shmat()** protection is not available on x86.
               Note that on systems supporting multiple ABIs (such as
               x86/x86-64) it is recommended to turn off alternative ABIs for
               services, so that they cannot be used to circumvent the
               restrictions of this option. Specifically, it is recommended
               to combine this option with _SystemCallArchitectures=native_ or
               similar.
    
               Added in version 231.
    
           _RestrictRealtime=_
               Takes a boolean argument. If set, any attempts to enable
               realtime scheduling in a process of the unit are refused. This
               restricts access to realtime task scheduling policies such as
               **SCHED_FIFO** , **SCHED_RR** or **SCHED_DEADLINE**. See sched(7) for
               details about these scheduling policies. Realtime scheduling
               policies may be used to monopolize CPU time for longer periods
               of time, and may hence be used to lock up or otherwise trigger
               Denial-of-Service situations on the system. It is hence
               recommended to restrict access to realtime scheduling to the
               few programs that actually require them. Defaults to off.
    
               Added in version 231.
    
           _RestrictSUIDSGID=_
               Takes a boolean argument. If set, any attempts to set the
               set-user-ID (SUID) or set-group-ID (SGID) bits on files or
               directories will be denied (for details on these bits see
               inode(7)). As the SUID/SGID bits are mechanisms to elevate
               privileges, and allow users to acquire the identity of other
               users, it is recommended to restrict creation of SUID/SGID
               files to the few programs that actually require them. Note
               that this restricts marking of any type of file system object
               with these bits, including both regular files and directories
               (where the SGID is a different meaning than for files, see
               documentation). This option is implied if _DynamicUser=_ is
               enabled.
    
               In other cases, this setting defaults to the value set with
               _DefaultRestrictSUIDSGID=_ in systemd-system.conf(5), which
               defaults to off.
    
               Added in version 242.
    
           _RemoveIPC=_
               Takes a boolean parameter. If set, all System V and POSIX IPC
               objects owned by the user and group the processes of this unit
               are run as are removed when the unit is stopped. This setting
               only has an effect if at least one of _User=_ , _Group=_ and
               _DynamicUser=_ are used. It has no effect on IPC objects owned
               by the root user. Specifically, this removes System V
               semaphores, as well as System V and POSIX shared memory
               segments and message queues. If multiple units use the same
               user or group the IPC objects are removed when the last of
               these units is stopped. This setting is implied if
               _DynamicUser=_ is set.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 232.
    
           _PrivateMounts=_
               Takes a boolean parameter. If set, the processes of this unit
               will be run in their own private file system (mount) namespace
               with all mount propagation from the processes towards the
               host's main file system namespace turned off. This means any
               file system mount points established or removed by the unit's
               processes will be private to them and not be visible to the
               host. However, file system mount points established or removed
               on the host will be propagated to the unit's processes. See
               mount_namespaces(7) for details on file system namespaces.
               Defaults to off.
    
               When turned on, this executes three operations for each
               invoked process: a new **CLONE_NEWNS** namespace is created, after
               which all existing mounts are remounted to **MS_SLAVE** to disable
               propagation from the unit's processes to the host (but leaving
               propagation in the opposite direction in effect). Finally, the
               mounts are remounted again to the propagation mode configured
               with _MountFlags=_ , see below.
    
               File system namespaces are set up individually for each
               process forked off by the service manager. Mounts established
               in the namespace of the process created by _ExecStartPre=_ will
               hence be cleaned up automatically as soon as that process
               exits and will not be available to subsequent processes forked
               off for _ExecStart=_ (and similar applies to the various other
               commands configured for units). Similarly, _JoinsNamespaceOf=_
               does not permit sharing kernel mount namespaces between units,
               it only enables sharing of the /tmp/ and /var/tmp/
               directories.
    
               Other file system namespace unit settings — _PrivateTmp=_ ,
               _PrivateDevices=_ , _ProtectSystem=_ , _ProtectHome=_ , _ReadOnlyPaths=_ ,
               _InaccessiblePaths=_ , _ReadWritePaths=_ , _BindPaths=_ ,
               _BindReadOnlyPaths=_ , ... — also enable file system namespacing
               in a fashion equivalent to this option. Hence it is primarily
               useful to explicitly request this behaviour if none of the
               other settings are used.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    
               Added in version 239.
    
           _MountFlags=_
               Takes a mount propagation setting: **shared** , **slave** or **private** ,
               which controls whether file system mount points in the file
               system namespaces set up for this unit's processes will
               receive or propagate mounts and unmounts from other file
               system namespaces. See mount(2) for details on mount
               propagation, and the three propagation flags in particular.
    
               This setting only controls the _final_ propagation setting in
               effect on all mount points of the file system namespace
               created for each process of this unit. Other file system
               namespacing unit settings (see the discussion in
               _PrivateMounts=_ above) will implicitly disable mount and
               unmount propagation from the unit's processes towards the host
               by changing the propagation setting of all mount points in the
               unit's file system namespace to **slave** first. Setting this
               option to **shared** does not reestablish propagation in that
               case.
    
               If not set – but file system namespaces are enabled through
               another file system namespace unit setting – **shared** mount
               propagation is used, but — as mentioned — as **slave** is applied
               first, propagation from the unit's processes to the host is
               still turned off.
    
               It is not recommended to use **private** mount propagation for
               units, as this means temporary mounts (such as removable
               media) of the host will stay mounted and thus indefinitely
               busy in forked off processes, as unmount propagation events
               will not be received by the file system namespace of the unit.
    
               Usually, it is best to leave this setting unmodified, and use
               higher level file system namespacing options instead, in
               particular _PrivateMounts=_ , see above.
    
               This option is only available for system services, or for
               services running in per-user instances of the service manager
               in which case _PrivateUsers=_ is implicitly enabled (requires
               unprivileged user namespaces support to be enabled in the
               kernel via the "kernel.unprivileged_userns_clone=" sysctl).
    


## SYSTEM CALL FILTERING



           _SystemCallFilter=_
               Takes a space-separated list of system call names or system
               call groups. If this setting is used, system calls executed by
               the unit processes except for the listed ones will result in
               the system call being denied (allow-listing). If the first
               character of the list is "~", the effect is inverted: only the
               listed system calls will be denied (deny-listing). This option
               may be specified more than once, in which case the filter
               masks are merged. If the empty string is assigned, the filter
               is reset, all prior assignments will have no effect.
    
               Commands prefixed with "+" are not subject to filtering. The
               **execve()** , **exit()** , **exit_group()** , **getrlimit()** , **rt_sigreturn()** ,
               **sigreturn()** system calls and the system calls for querying
               time and sleeping are implicitly allow-listed and do not need
               to be listed explicitly.
    
               The default action when a system call is denied is to
               terminate the processes with a **SIGSYS** signal. This can changed
               using _SystemCallErrorNumber=_ , see below. In addition,
               deny-listed system calls and system call groups may optionally
               be suffixed with a colon (":") and an argument in the same
               format as _SystemCallErrorNumber=_ , to take this action when the
               matching system call is made. This takes precedence over the
               action specified in _SystemCallErrorNumber=_.
    
               This feature makes use of the Secure Computing Mode 2
               interfaces of the kernel ('seccomp filtering') and is useful
               for enforcing a minimal sandboxing environment.
    
               Note that on systems supporting multiple ABIs (such as
               x86/x86-64) it is recommended to turn off alternative ABIs for
               services, so that they cannot be used to circumvent the
               restrictions of this option. Specifically, it is recommended
               to combine this option with _SystemCallArchitectures=native_ or
               similar.
    
               Note that strict system call filters may impact execution and
               error handling code paths of the service invocation.
               Specifically, access to the **execve()** system call is required
               for the execution of the service binary — if it is blocked
               service invocation will necessarily fail. Also, if execution
               of the service binary fails for some reason (for example:
               missing service executable), the error handling logic might
               require access to an additional set of system calls in order
               to process and log this failure correctly. It might be
               necessary to temporarily disable system call filters in order
               to allow debugging of such failures.
    
               If you specify both types of this option (i.e. allow-listing
               and deny-listing), the first encountered will take precedence
               and will dictate the default action (termination or approval
               of a system call). Then the next occurrences of this option
               will add or delete the listed system calls from the set of the
               filtered system calls, depending of its type and the default
               action. (For example, if you have started with an allow list
               rule for **read()** and **write()** , and right after it add a deny
               list rule for **write()** , then **write()** will be removed from the
               set.)
    
               As the number of possible system calls is large, predefined
               groups of system calls are provided. A group starts with "@"
               character, followed by name of the set.
    
               **Table 5. Currently predefined system call sets**
               ┌─────────────────┬──────────────────────────┐
               │ **Set** │ **Description** │
               ├─────────────────┼──────────────────────────┤
               │ @aio            │ Asynchronous I/O (‐      │
               │                 │ io_setup(2),             │
               │                 │ io_submit(2), and        │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @basic-io       │ System calls for basic   │
               │                 │ I/O: reading, writing,   │
               │                 │ seeking, file descriptor │
               │                 │ duplication and closing  │
               │                 │ (read(2), write(2), and  │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @chown          │ Changing file ownership  │
               │                 │ (chown(2), fchownat(2),  │
               │                 │ and related calls)       │
               ├─────────────────┼──────────────────────────┤
               │ @clock          │ System calls for         │
               │                 │ changing the system      │
               │                 │ clock (adjtimex(2),      │
               │                 │ settimeofday(2), and     │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @cpu-emulation  │ System calls for CPU     │
               │                 │ emulation functionality  │
               │                 │ (vm86(2) and related     │
               │                 │ calls)                   │
               ├─────────────────┼──────────────────────────┤
               │ @debug          │ Debugging, performance   │
               │                 │ monitoring and tracing   │
               │                 │ functionality (‐         │
               │                 │ ptrace(2),               │
               │                 │ perf_event_open(2) and   │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @file-system    │ File system operations:  │
               │                 │ opening, creating files  │
               │                 │ and directories for read │
               │                 │ and write, renaming and  │
               │                 │ removing them, reading   │
               │                 │ file properties, or      │
               │                 │ creating hard and        │
               │                 │ symbolic links           │
               ├─────────────────┼──────────────────────────┤
               │ @io-event       │ Event loop system calls  │
               │                 │ (poll(2), select(2),     │
               │                 │ epoll(7), eventfd(2) and │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @ipc            │ Pipes, SysV IPC, POSIX   │
               │                 │ Message Queues and other │
               │                 │ IPC (mq_overview(7),     │
               │                 │ svipc(7))                │
               ├─────────────────┼──────────────────────────┤
               │ @keyring        │ Kernel keyring access (‐ │
               │                 │ keyctl(2) and related    │
               │                 │ calls)                   │
               ├─────────────────┼──────────────────────────┤
               │ @memlock        │ Locking of memory in RAM │
               │                 │ (mlock(2), mlockall(2)   │
               │                 │ and related calls)       │
               ├─────────────────┼──────────────────────────┤
               │ @module         │ Loading and unloading of │
               │                 │ kernel modules (‐        │
               │                 │ init_module(2),          │
               │                 │ delete_module(2) and     │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @mount          │ Mounting and unmounting  │
               │                 │ of file systems (‐       │
               │                 │ mount(2), chroot(2), and │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @network-io     │ Socket I/O (including    │
               │                 │ local AF_UNIX):          │
               │                 │ socket(7), unix(7)       │
               ├─────────────────┼──────────────────────────┤
               │ @obsolete       │ Unusual, obsolete or     │
               │                 │ unimplemented (‐         │
               │                 │ create_module(2),        │
               │                 │ gtty(2), ...)            │
               ├─────────────────┼──────────────────────────┤
               │ @pkey           │ System calls that deal   │
               │                 │ with memory protection   │
               │                 │ keys (pkeys(7))          │
               ├─────────────────┼──────────────────────────┤
               │ @privileged     │ All system calls which   │
               │                 │ need super-user          │
               │                 │ capabilities (‐          │
               │                 │ capabilities(7))         │
               ├─────────────────┼──────────────────────────┤
               │ @process        │ Process control,         │
               │                 │ execution, namespacing   │
               │                 │ operations (clone(2),    │
               │                 │ kill(2), namespaces(7),  │
               │                 │ ...)                     │
               ├─────────────────┼──────────────────────────┤
               │ @raw-io         │ Raw I/O port access (‐   │
               │                 │ ioperm(2), iopl(2),      │
               │                 │ **pciconfig_read()** , ...)   │
               ├─────────────────┼──────────────────────────┤
               │ @reboot         │ System calls for         │
               │                 │ rebooting and reboot     │
               │                 │ preparation (reboot(2),  │
               │                 │ **kexec()** , ...)            │
               ├─────────────────┼──────────────────────────┤
               │ @resources      │ System calls for         │
               │                 │ changing resource        │
               │                 │ limits, memory and       │
               │                 │ scheduling parameters (‐ │
               │                 │ setrlimit(2),            │
               │                 │ setpriority(2), ...)     │
               ├─────────────────┼──────────────────────────┤
               │ @sandbox        │ System calls for         │
               │                 │ sandboxing programs (‐   │
               │                 │ seccomp(2), Landlock     │
               │                 │ system calls, ...)       │
               ├─────────────────┼──────────────────────────┤
               │ @setuid         │ System calls for         │
               │                 │ changing user ID and     │
               │                 │ group ID credentials, (‐ │
               │                 │ setuid(2), setgid(2),    │
               │                 │ setresuid(2), ...)       │
               ├─────────────────┼──────────────────────────┤
               │ @signal         │ System calls for         │
               │                 │ manipulating and         │
               │                 │ handling process signals │
               │                 │ (signal(2),              │
               │                 │ sigprocmask(2), ...)     │
               ├─────────────────┼──────────────────────────┤
               │ @swap           │ System calls for         │
               │                 │ enabling/disabling swap  │
               │                 │ devices (swapon(2),      │
               │                 │ swapoff(2))              │
               ├─────────────────┼──────────────────────────┤
               │ @sync           │ Synchronizing files and  │
               │                 │ memory to disk (‐        │
               │                 │ fsync(2), msync(2), and  │
               │                 │ related calls)           │
               ├─────────────────┼──────────────────────────┤
               │ @system-service │ A reasonable set of      │
               │                 │ system calls used by     │
               │                 │ common system services,  │
               │                 │ excluding any special    │
               │                 │ purpose calls. This is   │
               │                 │ the recommended starting │
               │                 │ point for allow-listing  │
               │                 │ system calls for system  │
               │                 │ services, as it contains │
               │                 │ what is typically needed │
               │                 │ by system services, but  │
               │                 │ excludes overly specific │
               │                 │ interfaces. For example, │
               │                 │ the following APIs are   │
               │                 │ excluded: "@clock",      │
               │                 │ "@mount", "@swap",       │
               │                 │ "@reboot".               │
               ├─────────────────┼──────────────────────────┤
               │ @timer          │ System calls for         │
               │                 │ scheduling operations by │
               │                 │ time (alarm(2),          │
               │                 │ timer_create(2), ...)    │
               ├─────────────────┼──────────────────────────┤
               │ @known          │ All system calls defined │
               │                 │ by the kernel. This list │
               │                 │ is defined statically in │
               │                 │ systemd based on a       │
               │                 │ kernel version that was  │
               │                 │ available when this      │
               │                 │ systemd version was      │
               │                 │ released. It will become │
               │                 │ progressively more       │
               │                 │ out-of-date as the       │
               │                 │ kernel is updated.       │
               └─────────────────┴──────────────────────────┘
    
               Note, that as new system calls are added to the kernel,
               additional system calls might be added to the groups above.
               Contents of the sets may also change between systemd versions.
               In addition, the list of system calls depends on the kernel
               version and architecture for which systemd was compiled. Use
               **systemd-analyze syscall-filter** to list the actual list of
               system calls in each filter.
    
               Generally, allow-listing system calls (rather than
               deny-listing) is the safer mode of operation. It is
               recommended to enforce system call allow lists for all
               long-running system services. Specifically, the following
               lines are a relatively safe basic choice for the majority of
               system services:
    
                   [Service]
                   SystemCallFilter=@system-service
                   SystemCallErrorNumber=EPERM
    
               Note that various kernel system calls are defined redundantly:
               there are multiple system calls for executing the same
               operation. For example, the **pidfd_send_signal()** system call
               may be used to execute operations similar to what can be done
               with the older **kill()** system call, hence blocking the latter
               without the former only provides weak protection. Since new
               system calls are added regularly to the kernel as development
               progresses, keeping system call deny lists comprehensive
               requires constant work. It is thus recommended to use
               allow-listing instead, which offers the benefit that new
               system calls are by default implicitly blocked until the allow
               list is updated.
    
               Also note that a number of system calls are required to be
               accessible for the dynamic linker to work. The dynamic linker
               is required for running most regular programs (specifically:
               all dynamic ELF binaries, which is how most distributions
               build packaged programs). This means that blocking these
               system calls (which include **open()** , **openat()** or **mmap()**) will
               make most programs typically shipped with generic
               distributions unusable.
    
               It is recommended to combine the file system namespacing
               related options with _SystemCallFilter=~@mount_ , in order to
               prohibit the unit's processes to undo the mappings.
               Specifically these are the options _PrivateTmp=_ ,
               _PrivateDevices=_ , _ProtectSystem=_ , _ProtectHome=_ ,
               _ProtectKernelTunables=_ , _ProtectControlGroups=_ ,
               _ProtectKernelLogs=_ , _ProtectClock=_ , _ReadOnlyPaths=_ ,
               _InaccessiblePaths=_ and _ReadWritePaths=_.
    
               Added in version 187.
    
           _SystemCallErrorNumber=_
               Takes an "errno" error number (between 1 and 4095) or errno
               name such as **EPERM** , **EACCES** or **EUCLEAN** , to return when the
               system call filter configured with _SystemCallFilter=_ is
               triggered, instead of terminating the process immediately. See
               errno(3) for a full list of error codes. When this setting is
               not used, or when the empty string or the special setting
               "kill" is assigned, the process will be terminated immediately
               when the filter is triggered.
    
               Added in version 209.
    
           _SystemCallArchitectures=_
               Takes a space-separated list of architecture identifiers to
               include in the system call filter. The known architecture
               identifiers are the same as for _ConditionArchitecture=_
               described in systemd.unit(5), as well as **x32** , **mips64-n32** ,
               **mips64-le-n32** , and the special identifier **native**. The special
               identifier **native** implicitly maps to the native architecture
               of the system (or more precisely: to the architecture the
               system manager is compiled for). By default, this option is
               set to the empty list, i.e. no filtering is applied.
    
               If this setting is used, processes of this unit will only be
               permitted to call native system calls, and system calls of the
               specified architectures. For the purposes of this option, the
               x32 architecture is treated as including x86-64 system calls.
               However, this setting still fulfills its purpose, as explained
               below, on x32.
    
               System call filtering is not equally effective on all
               architectures. For example, on x86 filtering of network
               socket-related calls is not possible, due to ABI limitations —
               a limitation that x86-64 does not have, however. On systems
               supporting multiple ABIs at the same time — such as x86/x86-64
               — it is hence recommended to limit the set of permitted system
               call architectures so that secondary ABIs may not be used to
               circumvent the restrictions applied to the native ABI of the
               system. In particular, setting _SystemCallArchitectures=native_
               is a good choice for disabling non-native ABIs.
    
               System call architectures may also be restricted system-wide
               via the _SystemCallArchitectures=_ option in the global
               configuration. See systemd-system.conf(5) for details.
    
               Added in version 209.
    
           _SystemCallLog=_
               Takes a space-separated list of system call names. If this
               setting is used, all system calls executed by the unit
               processes for the listed ones will be logged. If the first
               character of the list is "~", the effect is inverted: all
               system calls except the listed system calls will be logged.
               This feature makes use of the Secure Computing Mode 2
               interfaces of the kernel ('seccomp filtering') and is useful
               for auditing or setting up a minimal sandboxing environment.
               This option may be specified more than once, in which case the
               filter masks are merged. If the empty string is assigned, the
               filter is reset, all prior assignments will have no effect.
               This does not affect commands prefixed with "+".
    
               Added in version 247.
    


## ENVIRONMENT



           _Environment=_
               Sets environment variables for executed processes. Each line
               is unquoted using the rules described in "Quoting" section in
               systemd.syntax(7) and becomes a list of variable assignments.
               If you need to assign a value containing spaces or the equals
               sign to a variable, put quotes around the whole assignment.
               Variable expansion is not performed inside the strings and the
               "$" character has no special meaning. Specifier expansion is
               performed, see the "Specifiers" section in systemd.unit(5).
    
               This option may be specified more than once, in which case all
               listed variables will be set. If the same variable is listed
               twice, the later setting will override the earlier setting. If
               the empty string is assigned to this option, the list of
               environment variables is reset, all prior assignments have no
               effect.
    
               The names of the variables can contain ASCII letters, digits,
               and the underscore character. Variable names cannot be empty
               or start with a digit. In variable values, most characters are
               allowed, but non-printable characters are currently rejected.
    
               Example:
    
                   Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"
    
               gives three variables "VAR1", "VAR2", "VAR3" with the values
               "word1 word2", "word3", "$word 5 6".
    
               See environ(7) for details about environment variables.
    
               Note that environment variables are not suitable for passing
               secrets (such as passwords, key material, ...) to service
               processes. Environment variables set for a unit are exposed to
               unprivileged clients via D-Bus IPC, and generally not
               understood as being data that requires protection. Moreover,
               environment variables are propagated down the process tree,
               including across security boundaries (such as setuid/setgid
               executables), and hence might leak to processes that should
               not have access to the secret data. Use _LoadCredential=_ ,
               _LoadCredentialEncrypted=_ or _SetCredentialEncrypted=_ (see
               below) to pass data to unit processes securely.
    
           _EnvironmentFile=_
               Similar to _Environment=_ , but reads the environment variables
               from a text file. The text file should contain
               newline-separated variable assignments. Empty lines, lines
               without an "=" separator, or lines starting with ";" or "#"
               will be ignored, which may be used for commenting. The file
               must be encoded with UTF-8. Valid characters are **unicode**
               **scalar values******[14] other than**unicode noncharacters******[15],**U+0000**
               **NUL** , and **U+FEFF unicode byte order mark******[16]. Control codes
               other than**NUL** are allowed.
    
               In the file, an unquoted value after the "=" is parsed with
               the same backslash-escape rules as **POSIX shell unquoted**
               **text******[17], but unlike in a shell, interior whitespace is
               preserved and quotes after the first non-whitespace character
               are preserved. Leading and trailing whitespace (space, tab,
               carriage return) is discarded, but interior whitespace within
               the line is preserved verbatim. A line ending with a backslash
               will be continued to the following one, with the newline
               itself discarded. A backslash "\" followed by any character
               other than newline will preserve the following character, so
               that "\\" will become the value "\".
    
               In the file, a "'"-quoted value after the "=" can span
               multiple lines and contain any character verbatim other than
               single quote, like**POSIX shell single-quoted text******[18]. No
               backslash-escape sequences are recognized. Leading and
               trailing whitespace outside of the single quotes is discarded.
    
               In the file, a """-quoted value after the "=" can span
               multiple lines, and the same escape sequences are recognized
               as in**POSIX shell double-quoted text******[19]. Backslash ("\")
               followed by any of ""\`$" will preserve that character. A
               backslash followed by newline is a line continuation, and the
               newline itself is discarded. A backslash followed by any other
               character is ignored; both the backslash and the following
               character are preserved verbatim. Leading and trailing
               whitespace outside of the double quotes is discarded.
    
               The argument passed should be an absolute filename or wildcard
               expression, optionally prefixed with "-", which indicates that
               if the file does not exist, it will not be read and no error
               or warning message is logged. This option may be specified
               more than once in which case all specified files are read. If
               the empty string is assigned to this option, the list of file
               to read is reset, all prior assignments have no effect.
    
               The files listed with this directive will be read shortly
               before the process is executed (more specifically, after all
               processes from a previous unit state terminated. This means
               you can generate these files in one unit state, and read it
               with this option in the next. The files are read from the file
               system of the service manager, before any file system changes
               like bind mounts take place).
    
               Settings from these files override settings made with _Environment=_. If the same variable is set twice from these
               files, the files will be read in the order they are specified
               and the later setting will override the earlier setting.
    
           _PassEnvironment=_
               Pass environment variables set for the system service manager
               to executed processes. Takes a space-separated list of
               variable names. This option may be specified more than once,
               in which case all listed variables will be passed. If the
               empty string is assigned to this option, the list of
               environment variables to pass is reset, all prior assignments
               have no effect. Variables specified that are not set for the
               system manager will not be passed and will be silently
               ignored. Note that this option is only relevant for the system
               service manager, as system services by default do not
               automatically inherit any environment variables set for the
               service manager itself. However, in case of the user service
               manager all environment variables are passed to the executed
               processes anyway, hence this option is without effect for the
               user service manager.
    
               Variables set for invoked processes due to this setting are
               subject to being overridden by those configured with
               _Environment=_ or _EnvironmentFile=_.
    
               Example:
    
                   PassEnvironment=VAR1 VAR2 VAR3
    
               passes three variables "VAR1", "VAR2", "VAR3" with the values
               set for those variables in PID1.
    
               See environ(7) for details about environment variables.
    
               Added in version 228.
    
           _UnsetEnvironment=_
               Explicitly unset environment variable assignments that would
               normally be passed from the service manager to invoked
               processes of this unit. Takes a space-separated list of
               variable names or variable assignments. This option may be
               specified more than once, in which case all listed
               variables/assignments will be unset. If the empty string is
               assigned to this option, the list of environment
               variables/assignments to unset is reset. If a variable
               assignment is specified (that is: a variable name, followed by
               "=", followed by its value), then any environment variable
               matching this precise assignment is removed. If a variable
               name is specified (that is a variable name without any
               following "=" or value), then any assignment matching the
               variable name, regardless of its value is removed. Note that
               the effect of _UnsetEnvironment=_ is applied as final step when
               the environment list passed to executed processes is compiled.
               That means it may undo assignments from any configuration
               source, including assignments made through _Environment=_ or
               _EnvironmentFile=_ , inherited from the system manager's global
               set of environment variables, inherited via _PassEnvironment=_ ,
               set by the service manager itself (such as _$NOTIFY_SOCKET_ and
               such), or set by a PAM module (in case _PAMName=_ is used).
    
               See "Environment Variables in Spawned Processes" below for a
               description of how those settings combine to form the
               inherited environment. See environ(7) for general information
               about environment variables.
    
               Added in version 235.
    


## LOGGING AND STANDARD INPUT/OUTPUT



           _StandardInput=_
               Controls where file descriptor 0 (STDIN) of the executed
               processes is connected to. Takes one of **null** , **tty** , **tty-force** ,
               **tty-fail** , **data** , **file:**_path_ , **socket** or **fd:**_name_.
    
               If **null** is selected, standard input will be connected to
               /dev/null, i.e. all read attempts by the process will result
               in immediate EOF.
    
               If **tty** is selected, standard input is connected to a TTY (as
               configured by _TTYPath=_ , see below) and the executed process
               becomes the controlling process of the terminal. If the
               terminal is already being controlled by another process, the
               executed process waits until the current controlling process
               releases the terminal.
    
               **tty-force** is similar to **tty** , but the executed process is
               forcefully and immediately made the controlling process of the
               terminal, potentially removing previous controlling processes
               from the terminal.
    
               **tty-fail** is similar to **tty** , but if the terminal already has a
               controlling process start-up of the executed process fails.
    
               The **data** option may be used to configure arbitrary textual or
               binary data to pass via standard input to the executed
               process. The data to pass is configured via
               _StandardInputText=_ /_StandardInputData=_ (see below). Note that
               the actual file descriptor type passed (memory file, regular
               file, UNIX pipe, ...) might depend on the kernel and available
               privileges. In any case, the file descriptor is read-only, and
               when read returns the specified data followed by EOF.
    
               The **file:**_path_ option may be used to connect a specific file
               system object to standard input. An absolute path following
               the ":" character is expected, which may refer to a regular
               file, a FIFO or special file. If an **AF_UNIX** socket in the file
               system is specified, a stream socket is connected to it. The
               latter is useful for connecting standard input of processes to
               arbitrary system services.
    
               The **socket** option is valid in socket-activated services only,
               and requires the relevant socket unit file (see
               systemd.socket(5) for details) to have _Accept=yes_ set, or to
               specify a single socket only. If this option is set, standard
               input will be connected to the socket the service was
               activated from, which is primarily useful for compatibility
               with daemons designed for use with the traditional **inetd**(8)
               socket activation daemon (_$LISTEN_FDS_ (and related)
               environment variables are not passed when **socket** value is
               configured).
    
               The **fd:**_name_ option connects standard input to a specific,
               named file descriptor provided by a socket unit. The name may
               be specified as part of this option, following a ":" character
               (e.g.  "fd:foobar"). If no name is specified, the name "stdin"
               is implied (i.e.  "fd" is equivalent to "fd:stdin"). At least
               one socket unit defining the specified name must be provided
               via the _Sockets=_ option, and the file descriptor name may
               differ from the name of its containing socket unit. If
               multiple matches are found, the first one will be used. See
               _FileDescriptorName=_ in systemd.socket(5) for more details
               about named file descriptors and their ordering.
    
               This setting defaults to **null** , unless
               _StandardInputText=_ /_StandardInputData=_ are set, in which case
               it defaults to **data**.
    
           _StandardOutput=_
               Controls where file descriptor 1 (stdout) of the executed
               processes is connected to. Takes one of **inherit** , **null** , **tty** ,
               **journal** , **kmsg** , **journal+console** , **kmsg+console** , **file:**_path_ ,
               **append:**_path_ , **truncate:**_path_ , **socket** or **fd:**_name_.
    
               **inherit** duplicates the file descriptor of standard input for
               standard output.
    
               **null** connects standard output to /dev/null, i.e. everything
               written to it will be lost.
    
               **tty** connects standard output to a tty (as configured via
               _TTYPath=_ , see below). If the TTY is used for output only, the
               executed process will not become the controlling process of
               the terminal, and will not fail or wait for other processes to
               release the terminal. Note: if a unit tries to print multiple
               lines to a TTY during bootup or shutdown, then there's a
               chance that those lines will be broken up by status messages.
               **SetShowStatus()** can be used to prevent this problem. See
               org.freedesktop.systemd1(5) for details.
    
               **journal** connects standard output with the journal, which is
               accessible via journalctl(1). Note that everything that is
               written to kmsg (see below) is implicitly stored in the
               journal as well, the specific option listed below is hence a
               superset of this one. (Also note that any external, additional
               syslog daemons receive their log data from the journal, too,
               hence this is the option to use when logging shall be
               processed with such a daemon.)
    
               **kmsg** connects standard output with the kernel log buffer which
               is accessible via dmesg(1), in addition to the journal. The
               journal daemon might be configured to send all logs to kmsg
               anyway, in which case this option is no different from
               **journal**.
    
               **journal+console** and **kmsg+console** work in a similar way as the
               two options above but copy the output to the system console as
               well.
    
               The **file:**_path_ option may be used to connect a specific file
               system object to standard output. The semantics are similar to
               the same option of _StandardInput=_ , see above. If _path_ refers
               to a regular file on the filesystem, it is opened (created if
               it does not exist yet using privileges of the user executing
               the systemd process) for writing at the beginning of the file,
               but without truncating it. If standard input and output are
               directed to the same file path, it is opened only once — for
               reading as well as writing — and duplicated. This is
               particularly useful when the specified path refers to an
               **AF_UNIX** socket in the file system, as in that case only a
               single stream connection is created for both input and output.
    
               **append:**_path_ is similar to **file:**_path_ above, but it opens the
               file in append mode.
    
               **truncate:**_path_ is similar to **file:**_path_ above, but it truncates
               the file when opening it. For units with multiple command
               lines, e.g.  _Type=oneshot_ services with multiple _ExecStart=_ ,
               or services with _ExecCondition=_ , _ExecStartPre=_ or
               _ExecStartPost=_ , the output file is reopened and therefore
               re-truncated for each command line. If the output file is
               truncated while another process still has the file open, e.g.
               by an _ExecReload=_ running concurrently with an _ExecStart=_ , and
               the other process continues writing to the file without
               adjusting its offset, then the space between the file pointers
               of the two processes may be filled with **NUL** bytes, producing a
               sparse file. Thus, **truncate:**_path_ is typically only useful for
               units where only one process runs at a time, such as services
               with a single _ExecStart=_ and no _ExecStartPost=_ , _ExecReload=_ ,
               _ExecStop=_ or similar.
    
               **socket** connects standard output to a socket acquired via
               socket activation. The semantics are similar to the same
               option of _StandardInput=_ , see above.
    
               The **fd:**_name_ option connects standard output to a specific,
               named file descriptor provided by a socket unit. A name may be
               specified as part of this option, following a ":" character
               (e.g.  "fd:_foobar_ "). If no name is specified, the name
               "stdout" is implied (i.e.  "fd" is equivalent to "fd:stdout").
               At least one socket unit defining the specified name must be
               provided via the _Sockets=_ option, and the file descriptor name
               may differ from the name of its containing socket unit. If
               multiple matches are found, the first one will be used. See
               _FileDescriptorName=_ in systemd.socket(5) for more details
               about named descriptors and their ordering.
    
               If the standard output (or error output, see below) of a unit
               is connected to the journal or the kernel log buffer, the unit
               will implicitly gain a dependency of type _After=_ on
               systemd-journald.socket (also see the "Implicit Dependencies"
               section above). Also note that, in this case, stdout (or
               stderr, see below) will be an **AF_UNIX** stream socket, and not a
               pipe or FIFO that can be reopened. This means when executing
               shell scripts the construct **echo "hello" > /dev/stderr **for
               writing text to stderr will not work. To mitigate this use the
               construct **echo "hello" >&2 **instead, which is mostly equivalent
               and avoids this pitfall.
    
               If _StandardInput=_ is set to one of **tty** , **tty-force** , **tty-fail** ,
               **socket** , or **fd:**_name_ , this setting defaults to **inherit**.
    
               In other cases, this setting defaults to the value set with
               _DefaultStandardOutput=_ in systemd-system.conf(5), which
               defaults to **journal**. Note that setting this parameter might
               result in additional dependencies to be added to the unit (see
               above).
    
           _StandardError=_
               Controls where file descriptor 2 (stderr) of the executed
               processes is connected to. The available options are identical
               to those of _StandardOutput=_ , with some exceptions: if set to
               **inherit** the file descriptor used for standard output is
               duplicated for standard error, while **fd:**_name_ will use a
               default file descriptor name of "stderr".
    
               This setting defaults to the value set with
               _DefaultStandardError=_ in systemd-system.conf(5), which
               defaults to **inherit**. Note that setting this parameter might
               result in additional dependencies to be added to the unit (see
               above).
    
           _StandardInputText=_ , _StandardInputData=_
               Configures arbitrary textual or binary data to pass via file
               descriptor 0 (STDIN) to the executed processes. These settings
               have no effect unless _StandardInput=_ is set to **data**(which is
               the default if _StandardInput=_ is not set otherwise, but
               _StandardInputText=_ /_StandardInputData=_ is). Use this option to
               embed process input data directly in the unit file.
    
               _StandardInputText=_ accepts arbitrary textual data. C-style
               escapes for special characters as well as the usual
               "%"-specifiers are resolved. Each time this setting is used
               the specified text is appended to the per-unit data buffer,
               followed by a newline character (thus every use appends a new
               line to the end of the buffer). Note that leading and trailing
               whitespace of lines configured with this option is removed. If
               an empty line is specified the buffer is cleared (hence, in
               order to insert an empty line, add an additional "\n" to the
               end or beginning of a line).
    
               _StandardInputData=_ accepts arbitrary binary data, encoded in
               **Base64******[20]. No escape sequences or specifiers are resolved.
               Any whitespace in the encoded version is ignored during
               decoding.
    
               Note that _StandardInputText=_ and _StandardInputData=_ operate on
               the same data buffer, and may be mixed in order to configure
               both binary and textual data for the same input stream. The
               textual or binary data is joined strictly in the order the
               settings appear in the unit file. Assigning an empty string to
               either will reset the data buffer.
    
               Please keep in mind that in order to maintain readability long
               unit file settings may be split into multiple lines, by
               suffixing each line (except for the last) with a "\" character
               (see systemd.unit(5) for details). This is particularly useful
               for large data configured with these two options. Example:
    
                   ...
                   StandardInput=data
                   StandardInputData=V2XigLJyZSBubyBzdHJhbmdlcnMgdG8gbG92ZQpZb3Uga25vdyB0aGUgcnVsZXMgYW5kIHNvIGRv \
                                     IEkKQSBmdWxsIGNvbW1pdG1lbnQncyB3aGF0IEnigLJtIHRoaW5raW5nIG9mCllvdSB3b3VsZG4n \
                                     dCBnZXQgdGhpcyBmcm9tIGFueSBvdGhlciBndXkKSSBqdXN0IHdhbm5hIHRlbGwgeW91IGhvdyBJ \
                                     J20gZmVlbGluZwpHb3R0YSBtYWtlIHlvdSB1bmRlcnN0YW5kCgpOZXZlciBnb25uYSBnaXZlIHlv \
                                     dSB1cApOZXZlciBnb25uYSBsZXQgeW91IGRvd24KTmV2ZXIgZ29ubmEgcnVuIGFyb3VuZCBhbmQg \
                                     ZGVzZXJ0IHlvdQpOZXZlciBnb25uYSBtYWtlIHlvdSBjcnkKTmV2ZXIgZ29ubmEgc2F5IGdvb2Ri \
                                     eWUKTmV2ZXIgZ29ubmEgdGVsbCBhIGxpZSBhbmQgaHVydCB5b3UK
                   ...
    
               Added in version 236.
    
           _LogLevelMax=_
               Sets the maximum log level for log messages generated by this
               unit. Takes a **syslog** log level, one of **emerg**(lowest log
               level, only highest priority messages), **alert** , **crit** , **err** ,
               **warning** , **notice** , **info** , **debug**(highest log level, also lowest
               priority messages). See syslog(3) for details. By default, the
               maximum log level is not overridden.
    
               This option can be used to configure the logging system to
               drop log messages of a specific service above the specified
               level. For example, set _LogLevelMax=_**info** in order to turn off
               debug logging of a particularly chatty unit. Alternatively,
               this option can be used to enable extra logging about a
               specific unit by the system or user manager processes without
               changing the global log level for the system or user manager
               processes by setting _LogLevelMax=_**debug**.
    
               Note that the configured level is applied to any log messages
               written by any of the processes belonging to this unit, as
               well as any log messages written by the system or user manager
               processes in reference to this unit, sent via any supported
               logging protocol. The override is applied early in the logging
               pipeline, before any kind of further processing is done.
               Moreover, messages which pass through this filter successfully
               might still be dropped by filters applied at a later stage in
               the logging subsystem. For example, _MaxLevelStore=_ configured
               in journald.conf(5) might prohibit messages of higher log
               levels to be stored on disk, even though the per-unit
               _LogLevelMax=_ permitted it to be processed.
    
               Added in version 236.
    
           _LogExtraFields=_
               Configures additional log metadata fields to include in all
               log records generated by processes associated with this unit,
               including systemd. This setting takes one or more journal
               field assignments in the format "FIELD=VALUE" separated by
               whitespace. See systemd.journal-fields(7) for details on the
               journal field concept. Even though the underlying journal
               implementation permits binary field values, this setting
               accepts only valid UTF-8 values. To include space characters
               in a journal field value, enclose the assignment in double
               quotes (").  The usual specifiers are expanded in all
               assignments (see below). Note that this setting is not only
               useful for attaching additional metadata to log records of a
               unit, but given that all fields and values are indexed may
               also be used to implement cross-unit log record matching.
               Assign an empty string to reset the list.
    
               Note that this functionality is currently only available in
               system services, not in per-user services.
    
               Added in version 236.
    
           _LogRateLimitIntervalSec=_ , _LogRateLimitBurst=_
               Configures the rate limiting that is applied to log messages
               generated by this unit. If, in the time interval defined by
               _LogRateLimitIntervalSec=_ , more messages than specified in
               _LogRateLimitBurst=_ are logged by a service, all further
               messages within the interval are dropped until the interval is
               over. A message about the number of dropped messages is
               generated. The time specification for _LogRateLimitIntervalSec=_
               may be specified in the following units: "s", "min", "h",
               "ms", "us". See systemd.time(7) for details. The default
               settings are set by _RateLimitIntervalSec=_ and _RateLimitBurst=_
               configured in journald.conf(5). Note that this only applies to
               log messages that are processed by the logging subsystem, i.e.
               by systemd-journald.service(8). This means that if you connect
               a service's stderr directly to a file via
               _StandardOutput=file:..._  or a similar setting, the rate
               limiting will not be applied to messages written that way (but
               it will be enforced for messages generated via syslog(3) and
               similar functions).
    
               Added in version 240.
    
           _LogFilterPatterns=_
               Define an extended regular expression to filter log messages
               based on the _MESSAGE=_ field of the structured message. If the
               first character of the pattern is "~", log entries matching
               the pattern should be discarded. This option takes a single
               pattern as an argument but can be used multiple times to
               create a list of allowed and denied patterns. If the empty
               string is assigned, the filter is reset, and all prior
               assignments will have no effect.
    
               Because the "~" character is used to define denied patterns,
               it must be replaced with "\x7e" to allow a message starting
               with "~". For example, "~foobar" would add a pattern matching
               "foobar" to the deny list, while "\x7efoobar" would add a
               pattern matching "~foobar" to the allow list.
    
               Log messages are tested against denied patterns (if any), then
               against allowed patterns (if any). If a log message matches
               any of the denied patterns, it is discarded immediately
               without considering allowed patterns. Remaining log messages
               are tested against allowed patterns. Messages matching against
               none of the allowed pattern are discarded. If no allowed
               patterns are defined, then all messages are processed directly
               after going through denied filters.
    
               Filtering is based on the unit for which _LogFilterPatterns=_ is
               defined, meaning log messages coming from systemd(1) about the
               unit are not taken into account. Filtered log messages will
               not be forwarded to traditional syslog daemons, the kernel log
               buffer (kmsg), the systemd console, or sent as wall messages
               to all logged-in users.
    
               Note that this functionality is currently only available in
               system services, not in per-user services.
    
               Added in version 253.
    
           _LogNamespace=_
               Run the unit's processes in the specified journal namespace.
               Expects a short user-defined string identifying the namespace.
               If not used the processes of the service are run in the
               default journal namespace, i.e. their log stream is collected
               and processed by systemd-journald.service. If this option is
               used any log data generated by processes of this unit
               (regardless of whether via the **syslog()** , journal native
               logging or stdout/stderr logging) is collected and processed
               by an instance of the systemd-journald@.service template unit,
               which manages the specified namespace. The log data is stored
               in a data store independent from the default log namespace's
               data store. See systemd-journald.service(8) for details about
               journal namespaces.
    
               Internally, journal namespaces are implemented through Linux
               mount namespacing and over-mounting the directory that
               contains the relevant **AF_UNIX** sockets used for logging in the
               unit's mount namespace. Since mount namespaces are used this
               setting disconnects propagation of mounts from the unit's
               processes to the host, similarly to how _ReadOnlyPaths=_ and
               similar settings describe above work. Journal namespaces may
               hence not be used for services that need to establish mount
               points on the host.
    
               When this option is used the unit will automatically gain
               ordering and requirement dependencies on the two socket units
               associated with the systemd-journald@.service instance so that
               they are automatically established prior to the unit starting
               up. Note that when this option is used log output of this
               service does not appear in the regular journalctl(1) output,
               unless the **--namespace=** option is used.
    
               This option is only available for system services and is not
               supported for services running in per-user instances of the
               service manager.
    
               Added in version 245.
    
           _SyslogIdentifier=_
               Sets the process name ("**syslog** tag") to prefix log lines sent
               to the logging system or the kernel log buffer with. If not
               set, defaults to the process name of the executed process.
               This option is only useful when _StandardOutput=_ or
               _StandardError=_ are set to **journal** or **kmsg**(or to the same
               settings in combination with **+console**) and only applies to log
               messages written to stdout or stderr.
    
           _SyslogFacility=_
               Sets the **syslog** facility identifier to use when logging. One
               of **kern** , **user** , **mail** , **daemon** , **auth** , **syslog** , **lpr** , **news** , **uucp** ,
               **cron** , **authpriv** , **ftp** , **local0** , **local1** , **local2** , **local3** , **local4** ,
               **local5** , **local6** or **local7**. See syslog(3) for details. This
               option is only useful when _StandardOutput=_ or _StandardError=_
               are set to **journal** or **kmsg**(or to the same settings in
               combination with **+console**), and only applies to log messages
               written to stdout or stderr. Defaults to **daemon**.
    
           _SyslogLevel=_
               The default **syslog** log level to use when logging to the
               logging system or the kernel log buffer. One of **emerg** , **alert** ,
               **crit** , **err** , **warning** , **notice** , **info** , **debug**. See syslog(3) for
               details. This option is only useful when _StandardOutput=_ or
               _StandardError=_ are set to **journal** or **kmsg**(or to the same
               settings in combination with **+console**), and only applies to
               log messages written to stdout or stderr. Note that individual
               lines output by executed processes may be prefixed with a
               different log level which can be used to override the default
               log level specified here. The interpretation of these prefixes
               may be disabled with _SyslogLevelPrefix=_ , see below. For
               details, see sd-daemon(3). Defaults to **info**.
    
           _SyslogLevelPrefix=_
               Takes a boolean argument. If true and _StandardOutput=_ or
               _StandardError=_ are set to **journal** or **kmsg**(or to the same
               settings in combination with **+console**), log lines written by
               the executed process that are prefixed with a log level will
               be processed with this log level set but the prefix removed.
               If set to false, the interpretation of these prefixes is
               disabled and the logged lines are passed on as-is. This only
               applies to log messages written to stdout or stderr. For
               details about this prefixing see sd-daemon(3). Defaults to
               true.
    
           _TTYPath=_
               Sets the terminal device node to use if standard input,
               output, or error are connected to a TTY (see above). Defaults
               to /dev/console.
    
           _TTYReset=_
               Reset the terminal device specified with _TTYPath=_ before and
               after execution. This does not erase the screen (see
               _TTYVTDisallocate=_ below for that). Defaults to "no".
    
           _TTYVHangup=_
               Disconnect all clients which have opened the terminal device
               specified with _TTYPath=_ before and after execution. Defaults
               to "no".
    
           _TTYColumns=_ , _TTYRows=_
               Configure the size of the TTY specified with _TTYPath=_. If
               unset or set to the empty string, it is attempted to retrieve
               the dimensions of the terminal screen via ANSI sequences, and
               if that fails the kernel defaults (typically 80x24) are used.
    
               Added in version 250.
    
           _TTYVTDisallocate=_
               If the terminal device specified with _TTYPath=_ is a virtual
               console terminal, try to deallocate the TTY before and after
               execution. This ensures that the screen and scrollback buffer
               is cleared. If the terminal device is of any other type of TTY
               an attempt is made to clear the screen via ANSI sequences.
               Defaults to "no".
    


## CREDENTIALS



           _LoadCredential=ID_[:_PATH_], _LoadCredentialEncrypted=ID_[:_PATH_]
               Pass a credential to the unit. Credentials are limited-size
               binary or textual objects that may be passed to unit
               processes. They are primarily intended for passing
               cryptographic keys (both public and private) or certificates,
               user account information or identity information from host to
               services, but can be freely used to pass any kind of
               limited-size information to a service. The data is accessible
               from the unit's processes via the file system, at a read-only
               location that (if possible and permitted) is backed by
               non-swappable memory. The data is only accessible to the user
               associated with the unit, via the _User=_ /_DynamicUser=_ settings
               (as well as the superuser). When available, the location of
               credentials is exported as the _$CREDENTIALS_DIRECTORY_
               environment variable to the unit's processes.
    
               The _LoadCredential=_ setting takes a textual ID to use as name
               for a credential plus a file system path, separated by a
               colon. The ID must be a short ASCII string suitable as
               filename in the filesystem, and may be chosen freely by the
               user. If the specified path is absolute it is opened as
               regular file and the credential data is read from it. If the
               absolute path refers to an **AF_UNIX** stream socket in the file
               system a connection is made to it (once at process invocation)
               and the credential data read from the connection, providing an
               easy IPC integration point for dynamically transferring
               credentials from other services.
    
               If the specified path is not absolute and itself qualifies as
               valid credential identifier it is attempted to find a
               credential that the service manager itself received under the
               specified name — which may be used to propagate credentials
               from an invoking environment (e.g. a container manager that
               invoked the service manager) into a service. If no matching
               passed credential is found, the system service manager will
               search the directories /etc/credstore/, /run/credstore/ and
               /usr/lib/credstore/ for files under the credential's name —
               which hence are recommended locations for credential data on
               disk. If _LoadCredentialEncrypted=_ is used
               /run/credstore.encrypted/, /etc/credstore.encrypted/, and
               /usr/lib/credstore.encrypted/ are searched as well. The
               per-user service manager will search
               $XDG_CONFIG_HOME/credstore/, $XDG_RUNTIME_DIR/credstore/,
               $HOME/.local/lib/credstore/ (and the counterparts ending with
               .../credstore.encrypted/) instead. The systemd-path(1) tool
               may be used to query the precise credential store search path.
    
               If the file system path is omitted it is chosen identical to
               the credential name, i.e. this is a terse way to declare
               credentials to inherit from the service manager or credstore
               directories into a service. This option may be used multiple
               times, each time defining an additional credential to pass to
               the unit.
    
               Note that if the path is not specified or a valid credential
               identifier is given, i.e. in the above two cases, a missing
               credential is not considered fatal.
    
               If an absolute path referring to a directory is specified,
               every file in that directory (recursively) will be loaded as a
               separate credential. The ID for each credential will be the
               provided ID suffixed with "_$FILENAME" (e.g., "Key_file1").
               When loading from a directory, symlinks will be ignored.
    
               The contents of the file/socket may be arbitrary binary or
               textual data, including newline characters and **NUL** bytes.
    
               The _LoadCredentialEncrypted=_ setting is identical to
               _LoadCredential=_ , except that the credential data is decrypted
               and authenticated before being passed on to the executed
               processes. Specifically, the referenced path should refer to a
               file or socket with an encrypted credential, as implemented by
               systemd-creds(1). This credential is loaded, decrypted,
               authenticated and then passed to the application in plaintext
               form, in the same way a regular credential specified via
               _LoadCredential=_ would be. A credential configured this way may
               be symmetrically encrypted/authenticated with a secret key
               derived from the system's TPM2 security chip, or with a secret
               key stored in /var/lib/systemd/credential.secret, or with
               both. Using encrypted and authenticated credentials improves
               security as credentials are not stored in plaintext and only
               authenticated and decrypted into plaintext the moment a
               service requiring them is started. Moreover, credentials may
               be bound to the local hardware and installations, so that they
               cannot easily be analyzed offline, or be generated externally.
               See systemd.resource-control(5) for the details about
               _DevicePolicy=_ or _DeviceAllow=_.
    
               Note that encrypted credentials targeted for services of the
               per-user service manager must be encrypted with **systemd-creds**
               **encrypt --user** , and those for the system service manager
               without the **--user** switch. Encrypted credentials are always
               targeted to a specific user or the system as a whole, and it
               is ensured that per-user service managers cannot decrypt
               secrets intended for the system or for other users.
    
               The credential files/IPC sockets must be accessible to the
               service manager, but do not have to be directly accessible to
               the unit's processes: the credential data is read and copied
               into separate, read-only copies for the unit that are
               accessible to appropriately privileged processes. This is
               particularly useful in combination with _DynamicUser=_ as this
               way privileged data can be made available to processes running
               under a dynamic UID (i.e. not a previously known one) without
               having to open up access to all users.
    
               In order to reference the path a credential may be read from
               within a _ExecStart=_ command line use
               "${CREDENTIALS_DIRECTORY}/mycred", e.g.  "ExecStart=cat
               ${CREDENTIALS_DIRECTORY}/mycred". In order to reference the
               path a credential may be read from within a _Environment=_ line
               use "%d/mycred", e.g.  "Environment=MYCREDPATH=%d/mycred". For
               system services the path may also be referenced as
               "/run/credentials/_UNITNAME_ " in cases where no interpolation is
               possible, e.g. configuration files of software that does not
               yet support credentials natively.  _$CREDENTIALS_DIRECTORY_ is
               considered the primary interface to look for credentials,
               though, since it also works for user services.
    
               Currently, an accumulated credential size limit of 1 MB per
               unit is enforced.
    
               The service manager itself may receive system credentials that
               can be propagated to services from a hosting container manager
               or VM hypervisor. See the **Container Interface******[21]
               documentation for details about the former. For the latter,
               pass**DMI/SMBIOS******[22] OEM string table entries (field type 11)
               with a prefix of "io.systemd.credential:" or
               "io.systemd.credential.binary:". In both cases a key/value
               pair separated by "=" is expected. In the latter case, the
               right-hand side is Base64 decoded when parsed (thus permitting
               binary data to be passed in). Example**qemu******[23] switch:
               "-smbios type=11,value=io.systemd.credential:xx=yy", or
               "-smbios
               type=11,value=io.systemd.credential.binary:rick=TmV2ZXIgR29ubmEgR2l2ZSBZb3UgVXA=".
               Alternatively, use the**qemu** "fw_cfg" node
               "opt/io.systemd.credentials/". Example **qemu** switch: "-fw_cfg
               name=opt/io.systemd.credentials/mycred,string=supersecret".
               They may also be passed from the UEFI firmware environment via
               systemd-stub(7), from the initrd (see systemd(1)), or be
               specified on the kernel command line using the
               "systemd.set_credential=" and "systemd.set_credential_binary="
               switches (see systemd(1) – this is not recommended since
               unprivileged userspace can read the kernel command line).
    
               If referencing an **AF_UNIX** stream socket to connect to, the
               connection will originate from an abstract namespace socket,
               that includes information about the unit and the credential ID
               in its socket name. Use getpeername(2) to query this
               information. The returned socket name is formatted as **NUL**
               _RANDOM_ "/unit/" _UNIT_ "/" _ID_ , i.e. a **NUL** byte (as required for
               abstract namespace socket names), followed by a random string
               (consisting of alphadecimal characters), followed by the
               literal string "/unit/", followed by the requesting unit name,
               followed by the literal character "/", followed by the textual
               credential ID requested. Example:
               "\0adf9d86b6eda275e/unit/foobar.service/credx" in case the
               credential "credx" is requested for a unit "foobar.service".
               This functionality is useful for using a single listening
               socket to serve credentials to multiple consumers.
    
               For further information see **System and Service Credentials******[24]
               documentation.
    
               Added in version 247._ImportCredential=GLOB_
               Pass one or more credentials to the unit. Takes a credential
               name for which we will attempt to find a credential that the
               service manager itself received under the specified name —
               which may be used to propagate credentials from an invoking
               environment (e.g. a container manager that invoked the service
               manager) into a service. If the credential name is a glob, all
               credentials matching the glob are passed to the unit. Matching
               credentials are searched for in the system credentials, the
               encrypted system credentials, and under /etc/credstore/,
               /run/credstore/, /usr/lib/credstore/,
               /run/credstore.encrypted/, /etc/credstore.encrypted/, and
               /usr/lib/credstore.encrypted/ in that order. When multiple
               credentials of the same name are found, the first one found is
               used.
    
               The globbing expression implements a restrictive subset of
               glob(7): only a single trailing "*" wildcard may be specified.
               Both "?"  and "[]" wildcards are not permitted, nor are "*"
               wildcards anywhere except at the end of the glob expression.
    
               Optionally, the credential name or glob may be followed by a
               colon followed by a rename pattern. If specified, all
               credentials matching the credential name or glob are renamed
               according to the given pattern. For example, if
               "ImportCredential=my.original.cred:my.renamed.cred" is
               specified, the service manager will read the
               "my.original.cred" credential and make it available as the
               "my.renamed.cred" credential to the service. Similarly, if
               "ImportCredential=my.original.*:my.renamed."  is specified,
               the service manager will read all credentials starting with
               "my.original."  and make them available as "my.renamed.xxx" to
               the service.
    
               If _ImportCredential=_ is specified multiple times and multiple
               credentials end up with the same name after renaming, the
               first one is kept and later ones are dropped.
    
               When multiple credentials of the same name are found,
               credentials found by _LoadCredential=_ and
               _LoadCredentialEncrypted=_ take priority over credentials found
               by _ImportCredential=_.
    
               Added in version 254.
    
           _SetCredential=ID_ :_VALUE_ , _SetCredentialEncrypted=ID_ :_VALUE_
               The _SetCredential=_ setting is similar to _LoadCredential=_ but
               accepts a literal value to use as data for the credential,
               instead of a file system path to read the data from. Do not
               use this option for data that is supposed to be secret, as it
               is accessible to unprivileged processes via IPC. It's only
               safe to use this for user IDs, public key material and similar
               non-sensitive data. For everything else use _LoadCredential=_.
               In order to embed binary data into the credential data use
               C-style escaping (i.e.  "\n" to embed a newline, or "\x00" to
               embed a **NUL** byte).
    
               The _SetCredentialEncrypted=_ setting is identical to
               _SetCredential=_ but expects an encrypted credential in literal
               form as value. This allows embedding confidential credentials
               securely directly in unit files. Use systemd-creds(1)' **-p**
               switch to generate suitable _SetCredentialEncrypted=_ lines
               directly from plaintext credentials. For further details see
               _LoadCredentialEncrypted=_ above.
    
               When multiple credentials of the same name are found,
               credentials found by _LoadCredential=_ , _LoadCredentialEncrypted=_
               and _ImportCredential=_ take priority over credentials found by
               _SetCredential=_. As such, _SetCredential=_ will act as default if
               no credentials are found by any of the former. In this case,
               not being able to retrieve the credential from the path
               specified in _LoadCredential=_ or _LoadCredentialEncrypted=_ is
               not considered fatal.
    
               Added in version 247.
    


## SYSTEM V COMPATIBILITY



           _UtmpIdentifier=_
               Takes a four character identifier string for an utmp(5) and
               wtmp entry for this service. This should only be set for
               services such as **getty** implementations (such as agetty(8))
               where utmp/wtmp entries must be created and cleared before and
               after execution, or for services that shall be executed as if
               they were run by a **getty** process (see below). If the
               configured string is longer than four characters, it is
               truncated and the terminal four characters are used. This
               setting interprets %I style string replacements. This setting
               is unset by default, i.e. no utmp/wtmp entries are created or
               cleaned up for this service.
    
           _UtmpMode=_
               Takes one of "init", "login" or "user". If _UtmpIdentifier=_ is
               set, controls which type of utmp(5)/wtmp entries for this
               service are generated. This setting has no effect unless
               _UtmpIdentifier=_ is set too. If "init" is set, only an
               **INIT_PROCESS** entry is generated and the invoked process must
               implement a **getty** -compatible utmp/wtmp logic. If "login" is
               set, first an **INIT_PROCESS** entry, followed by a **LOGIN_PROCESS**
               entry is generated. In this case, the invoked process must
               implement a login(1)-compatible utmp/wtmp logic. If "user" is
               set, first an **INIT_PROCESS** entry, then a **LOGIN_PROCESS** entry
               and finally a **USER_PROCESS** entry is generated. In this case,
               the invoked process may be any process that is suitable to be
               run as session leader. Defaults to "init".
    
               Added in version 225.
    


## ENVIRONMENT VARIABLES IN SPAWNED PROCESSES



           Processes started by the service manager are executed with an
           environment variable block assembled from multiple sources.
           Processes started by the system service manager generally do not
           inherit environment variables set for the service manager itself
           (but this may be altered via _PassEnvironment=_), but processes
           started by the user service manager instances generally do inherit
           all environment variables set for the service manager itself.
    
           For each invoked process the list of environment variables set is
           compiled from the following sources:
    
           •   Variables globally configured for the service manager, using
               the _DefaultEnvironment=_ setting in systemd-system.conf(5), the
               kernel command line option _systemd.setenv=_ understood by
               systemd(1), or via systemctl(1) **set-environment** verb.
    
           •   Variables defined by the service manager itself (see the list
               below).
    
           •   Variables set in the service manager's own environment
               variable block (subject to _PassEnvironment=_ for the system
               service manager).
    
           •   Variables set via _Environment=_ in the unit file.
    
           •   Variables read from files specified via _EnvironmentFile=_ in
               the unit file.
    
           •   Variables set by any PAM modules in case _PAMName=_ is in
               effect, cf. pam_env(8).
    
           If the same environment variable is set by multiple of these
           sources, the later source — according to the order of the list
           above — wins. Note that as the final step all variables listed in
           _UnsetEnvironment=_ are removed from the compiled environment
           variable list, immediately before it is passed to the executed
           process.
    
           The general philosophy is to expose a small curated list of
           environment variables to processes. Services started by the system
           manager (PID 1) will be started, without additional
           service-specific configuration, with just a few environment
           variables. The user manager inherits environment variables as any
           other system service, but in addition may receive additional
           environment variables from PAM, and, typically, additional
           imported variables when the user starts a graphical session. It is
           recommended to keep the environment blocks in both the system and
           user managers lean. Importing all variables inherited by the
           graphical session or by one of the user shells is strongly
           discouraged.
    
           Hint: **systemd-run -P env** and **systemd-run --user -P env** print the
           effective system and user service environment blocks.
    
       **Environment Variables Set or Propagated by the Service Manager**
           The following environment variables are propagated by the service
           manager or generated internally for each invoked process:
    
           _$PATH_
               Colon-separated list of directories to use when launching
               executables.  **systemd** uses a fixed value of
               "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin" in the
               system manager. In case of the user manager, a different path
               may be configured by the distribution. It is recommended to
               not rely on the order of entries, and have only one program
               with a given name in _$PATH_.
    
               Added in version 208.
    
           _$LANG_
               Locale. Can be set in locale.conf(5) or on the kernel command
               line (see systemd(1) and kernel-command-line(7)).
    
               Added in version 208.
    
           _$USER_ , _$LOGNAME_ , _$HOME_ , _$SHELL_
               User name (twice), home directory, and the login shell.  _$USER_
               is set unconditionally, while _$HOME_ , _$LOGNAME_ , and _$SHELL_ are
               only set for the units that have _User=_ set and
               _SetLoginEnvironment=_ unset or set to true. For user services,
               these variables are typically inherited from the user manager
               itself. See passwd(5).
    
               Added in version 208.
    
           _$INVOCATION_ID_
               Contains a randomized, unique 128-bit ID identifying each
               runtime cycle of the unit, formatted as 32 character
               hexadecimal string. A new ID is assigned each time the unit
               changes from an inactive state into an activating or active
               state, and may be used to identify this specific runtime
               cycle, in particular in data stored offline, such as the
               journal. The same ID is passed to all processes run as part of
               the unit.
    
               Added in version 232.
    
           _$XDG_RUNTIME_DIR_
               The directory to use for runtime objects (such as IPC objects)
               and volatile state. Set for all services run by the user
               **systemd** instance, as well as any system services that use
               _PAMName=_ with a PAM stack that includes **pam_systemd**. See below
               and pam_systemd(8) for more information.
    
               Added in version 208.
    
           _$RUNTIME_DIRECTORY_ , _$STATE_DIRECTORY_ , _$CACHE_DIRECTORY_ ,
           _$LOGS_DIRECTORY_ , _$CONFIGURATION_DIRECTORY_
               Absolute paths to the directories defined with
               _RuntimeDirectory=_ , _StateDirectory=_ , _CacheDirectory=_ ,
               _LogsDirectory=_ , and _ConfigurationDirectory=_ when those
               settings are used.
    
               Added in version 244.
    
           _$CREDENTIALS_DIRECTORY_
               An absolute path to the per-unit directory with credentials
               configured via
               _ImportCredential=_ /_LoadCredential=_ /_SetCredential=_. The
               directory is marked read-only and is placed in unswappable
               memory (if supported and permitted), and is only accessible to
               the UID associated with the unit via _User=_ or _DynamicUser=_
               (and the superuser).
    
               Added in version 247.
    
           _$TMPDIR_
               The environment variable is set to "/tmp" when
               _PrivateTmp=disconnected_ specified with _DefaultDependencies=no_
               and without _RootDirectory=/RootImage=_ and
               _RequiresMountsFor=/WantsMountsFor=_ for /var/. See explanation
               for _PrivateTmp=_ above.
    
               Added in version 258.
    
           _$MAINPID_
               The UNIX process ID (PID) of the unit's main process if it is
               known. This is only set for control processes as invoked by
               _ExecReload=_ and similar.
    
               Added in version 209.
    
           _$MAINPIDFDID_
               The 64bit inode ID of the file descriptor returned by
               **pidfd_open**(3) for the main process (if supported). This is
               only set for control processes as invoked by _ExecReload=_ and
               similar.
    
               Added in version 258.
    
           _$MANAGERPID_
               The PID of the per-user **systemd** service manager instance, set
               for processes spawned by it.
    
               Added in version 208.
    
           _$MANAGERPIDFDID_
               The **pidfd_open()** inode ID (see above) of the per-user **systemd**
               service manager instance, set for processes spawned by it.
    
               Added in version 258.
    
           _$LISTEN_FDS_ , _$LISTEN_PID_ , _$LISTEN_FDNAMES_
               Information about file descriptors passed to a service for
               socket activation. See sd_listen_fds(3).
    
               Added in version 208.
    
           _$NOTIFY_SOCKET_
               The socket **sd_notify()** talks to. See sd_notify(3).
    
               Added in version 229.
    
           _$WATCHDOG_PID_ , _$WATCHDOG_USEC_
               Information about watchdog keep-alive notifications. See
               sd_watchdog_enabled(3).
    
               Added in version 229.
    
           _$SYSTEMD_EXEC_PID_
               The PID of the unit process (e.g. process invoked by
               _ExecStart=_). The child process can use this information to
               determine whether the process is directly invoked by the
               service manager or indirectly as a child of another process by
               comparing this value with the current PID (similarly to the
               scheme used in sd_listen_fds(3) with _$LISTEN_PID_ and
               _$LISTEN_FDS_).
    
               Added in version 248.
    
           _$TERM_
               Terminal type, set only for units connected to a terminal
               (_StandardInput=tty_ , _StandardOutput=tty_ , or _StandardError=tty_).
               See termcap(5).
    
               Added in version 209.
    
           _$LOG_NAMESPACE_
               Contains the name of the selected logging namespace when the
               _LogNamespace=_ service setting is used.
    
               Added in version 246.
    
           _$JOURNAL_STREAM_
               If the standard output or standard error output of the
               executed processes are connected to the journal (for example,
               by setting _StandardError=journal_) _$JOURNAL_STREAM_ contains the
               device and inode numbers of the connection file descriptor,
               formatted in decimal, separated by a colon (":"). This permits
               invoked processes to safely detect whether their standard
               output or standard error output are connected to the journal.
               The device and inode numbers of the file descriptors should be
               compared with the values set in the environment variable to
               determine whether the process output is still connected to the
               journal. Note that it is generally not sufficient to only
               check whether _$JOURNAL_STREAM_ is set at all as services might
               invoke external processes replacing their standard output or
               standard error output, without unsetting the environment
               variable.
    
               If both standard output and standard error of the executed
               processes are connected to the journal via a stream socket,
               this environment variable will contain information about the
               standard error stream, as that's usually the preferred
               destination for log data. (Note that typically the same stream
               is used for both standard output and standard error, hence
               very likely the environment variable contains device and inode
               information matching both stream file descriptors.)
    
               This environment variable is primarily useful to allow
               services to optionally upgrade their used log protocol to the
               native journal protocol (using sd_journal_print(3) and other
               functions) if their standard output or standard error output
               is connected to the journal anyway, thus enabling delivery of
               structured metadata along with logged messages.
    
               Added in version 231.
    
           _$SERVICE_RESULT_
               Only used for the service unit type. This environment variable
               is passed to all _ExecStop=_ and _ExecStopPost=_ processes, and
               encodes the service "result". Currently, the following values
               are defined:
    
               **Table 6. Defined** _$SERVICE_RESULT_ values
               ┌───────────────────┬──────────────────────────┐
               │ **Value** │ **Meaning** │
               ├───────────────────┼──────────────────────────┤
               │ "success"         │ The service ran          │
               │                   │ successfully and exited  │
               │                   │ cleanly.                 │
               ├───────────────────┼──────────────────────────┤
               │ "protocol"        │ A protocol violation     │
               │                   │ occurred: the service    │
               │                   │ did not take the steps   │
               │                   │ required by its unit     │
               │                   │ configuration            │
               │                   │ (specifically what is    │
               │                   │ configured in its _Type=_  │
               │                   │ setting).                │
               ├───────────────────┼──────────────────────────┤
               │ "timeout"         │ One of the steps timed   │
               │                   │ out.                     │
               ├───────────────────┼──────────────────────────┤
               │ "exit-code"       │ Service process exited   │
               │                   │ with a non-zero exit     │
               │                   │ code; see _$EXIT_CODE_     │
               │                   │ below for the actual     │
               │                   │ exit code returned.      │
               ├───────────────────┼──────────────────────────┤
               │ "signal"          │ A service process was    │
               │                   │ terminated abnormally by │
               │                   │ a signal, without        │
               │                   │ dumping core. See        │
               │                   │ _$EXIT_CODE_ below for the │
               │                   │ actual signal causing    │
               │                   │ the termination.         │
               ├───────────────────┼──────────────────────────┤
               │ "core-dump"       │ A service process        │
               │                   │ terminated abnormally    │
               │                   │ with a signal and dumped │
               │                   │ core. See _$EXIT_CODE_     │
               │                   │ below for the signal     │
               │                   │ causing the termination. │
               ├───────────────────┼──────────────────────────┤
               │ "watchdog"        │ Watchdog keep-alive ping │
               │                   │ was enabled for the      │
               │                   │ service, but the         │
               │                   │ deadline was missed.     │
               ├───────────────────┼──────────────────────────┤
               │ "exec-condition"  │ Service did not run      │
               │                   │ because _ExecCondition=_   │
               │                   │ failed.                  │
               ├───────────────────┼──────────────────────────┤
               │ "oom-kill"        │ A service process was    │
               │                   │ terminated by the        │
               │                   │ Out-Of-Memory (OOM)      │
               │                   │ killer.                  │
               ├───────────────────┼──────────────────────────┤
               │ "start-limit-hit" │ A start limit was        │
               │                   │ defined for the unit and │
               │                   │ it was hit, causing the  │
               │                   │ unit to fail to start.   │
               │                   │ See systemd.unit(5)'s    │
               │                   │ _StartLimitIntervalSec=_   │
               │                   │ and _StartLimitBurst=_ for │
               │                   │ details.                 │
               ├───────────────────┼──────────────────────────┤
               │ "resources"       │ A catch-all condition in │
               │                   │ case a system operation  │
               │                   │ failed.                  │
               └───────────────────┴──────────────────────────┘
    
               This environment variable is useful to monitor failure or
               successful termination of a service. Even though this variable
               is available in both _ExecStop=_ and _ExecStopPost=_ , it is
               usually a better choice to place monitoring tools in the
               latter, as the former is only invoked for services that
               managed to start up correctly, and the latter covers both
               services that failed during their start-up and those which
               failed during their runtime.
    
               Added in version 232.
    
           _$EXIT_CODE_ , _$EXIT_STATUS_
               Only defined for the service unit type. These environment
               variables are passed to all _ExecStop=_ , _ExecStopPost=_ processes
               and contain exit status/code information of the main process
               of the service. For the precise definition of the exit code
               and status, see wait(2).  _$EXIT_CODE_ is one of "exited",
               "killed", "dumped".  _$EXIT_STATUS_ contains the numeric exit
               code formatted as string if _$EXIT_CODE_ is "exited", and the
               signal name in all other cases. Note that these environment
               variables are only set if the service manager succeeded to
               start and identify the main process of the service.
    
               **Table 7. Summary of possible service result variable values**
               ┌───────────────────┬──────────────────┬──────────────────┐
               │ _$SERVICE_RESULT_   │ _$EXIT_CODE_       │ _$EXIT_STATUS_     │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "success"         │ "killed"         │ "HUP", "INT",    │
               │                   │                  │ "TERM", "PIPE"   │
               │                   ├──────────────────┼──────────────────┤
               │                   │ "exited"         │ "0"              │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "protocol"        │ not set          │ not set          │
               │                   ├──────────────────┼──────────────────┤
               │                   │ "exited"         │ "0"              │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "timeout"         │ "killed"         │ "TERM", "KILL"   │
               │                   ├──────────────────┼──────────────────┤
               │                   │ "exited"         │ "0", "1", "2",   │
               │                   │                  │ "3", ..., "255"  │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "exit-code"       │ "exited"         │ "1", "2", "3",   │
               │                   │                  │ ..., "255"       │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "signal"          │ "killed"         │ "HUP", "INT",    │
               │                   │                  │ "KILL", ...      │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "core-dump"       │ "dumped"         │ "ABRT", "SEGV",  │
               │                   │                  │ "QUIT", ...      │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "watchdog"        │ "dumped"         │ "ABRT"           │
               │                   ├──────────────────┼──────────────────┤
               │                   │ "killed"         │ "TERM", "KILL"   │
               │                   ├──────────────────┼──────────────────┤
               │                   │ "exited"         │ "0", "1", "2",   │
               │                   │                  │ "3", ..., "255"  │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "exec-condition"  │ "exited"         │ "1", "2", "3",   │
               │                   │                  │ "4", ..., "254"  │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "oom-kill"        │ "killed"         │ "TERM", "KILL"   │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "start-limit-hit" │ not set          │ not set          │
               ├───────────────────┼──────────────────┼──────────────────┤
               │ "resources"       │ any of the above │ any of the above │
               ├───────────────────┴──────────────────┴──────────────────┤
               │ Note: the process may be also terminated by a signal    │
               │ not sent by systemd. In particular the process may send │
               │ an arbitrary signal to itself in a handler for any of   │
               │ the non-maskable signals. Nevertheless, in the          │
               │ "timeout" and "watchdog" rows above only the signals    │
               │ that systemd sends have been included. Moreover, using  │
               │ _SuccessExitStatus=_ additional exit statuses may be      │
               │ declared to indicate clean termination, which is not    │
               │ reflected by this table.                                │
               └─────────────────────────────────────────────────────────┘
    
               Added in version 232.
    
           _$MONITOR_SERVICE_RESULT_ , _$MONITOR_EXIT_CODE_ , _$MONITOR_EXIT_STATUS_ ,
           _$MONITOR_INVOCATION_ID_ , _$MONITOR_UNIT_
               Only defined for the service unit type. Those environment
               variables are passed to all _ExecStart=_ and _ExecStartPre=_
               processes which run in services triggered by _OnFailure=_ or
               _OnSuccess=_ dependencies.
    
               Variables _$MONITOR_SERVICE_RESULT_ , _$MONITOR_EXIT_CODE_ and
               _$MONITOR_EXIT_STATUS_ take the same values as for _ExecStop=_ and
               _ExecStopPost=_ processes. Variables _$MONITOR_INVOCATION_ID_ and
               _$MONITOR_UNIT_ are set to the invocation id and unit name of
               the service which triggered the dependency.
    
               Note that when multiple services specify the same unit as
               their _OnFailure=_ or _OnSuccess=_ handler, those variables will
               _not_ be passed. Consider using a template handler unit for that
               case instead: "OnFailure=_handler_ @%n.service" for non-templated
               units, or "OnFailure=_handler_ @%p-%i.service" for templated
               units.
    
               Added in version 251.
    
           _$PIDFILE_
               The path to the configured PID file, in case the process is
               forked off on behalf of a service that uses the _PIDFile=_
               setting, see systemd.service(5) for details. Service code may
               use this environment variable to automatically generate a PID
               file at the location configured in the unit file. This field
               is set to an absolute path in the file system.
    
               Added in version 242.
    
           _$REMOTE_ADDR_ , _$REMOTE_PORT_
               If this is a unit started via per-connection socket activation
               (i.e. via a socket unit with _Accept=yes_), these environment
               variables contain information about the remote peer of the
               socket connection.
    
               For IPv4 and IPv6 connections, _$REMOTE_ADDR_ contains the IP
               address, and _$REMOTE_PORT_ contains the port number of the
               remote peer.
    
               For **AF_UNIX** socket connections, _$REMOTE_ADDR_ contains either
               the remote socket's file system path starting with a slash
               ("/"), its address in the abstract namespace starting with an
               at symbol ("@"), or is unset in case of an unnamed socket.
               _$REMOTE_PORT_ is not set for **AF_UNIX** sockets.
    
               Added in version 220.
    
           _$SO_COOKIE_
               If this is a unit started via per-connection socket activation
               (i.e. via a socket unit with _Accept=yes_), this environment
               variable contains the Linux socket cookie, formatted as
               decimal integer. The socket cookie can otherwise be acquired
               via **getsockopt**(7).
    
               Added in version 258.
    
           _$TRIGGER_UNIT_ , _$TRIGGER_PATH_ , _$TRIGGER_TIMER_REALTIME_USEC_ ,
           _$TRIGGER_TIMER_MONOTONIC_USEC_
               If the unit was activated dynamically (e.g.: a corresponding
               path unit or timer unit), the unit that triggered it and other
               type-dependent information will be passed via these variables.
               Note that this information is provided in a best-effort way.
               For example, multiple triggers happening one after another
               will be coalesced and only one will be reported, with no
               guarantee as to which one it will be. Because of this, in most
               cases this variable will be primarily informational, i.e.
               useful for debugging purposes, is lossy, and should not be
               relied upon to propagate a comprehensive reason for
               activation.
    
               Added in version 252.
    
           _$MEMORY_PRESSURE_WATCH_ , _$MEMORY_PRESSURE_WRITE_
               If memory pressure monitoring is enabled for this service
               unit, the path to watch and the data to write into it. See
               **Memory Pressure Handling******[25] for details about these variables
               and the service protocol data they convey.
    
               Added in version 254._$FDSTORE_
               The maximum number of file descriptors that may be stored in
               the manager for the service. This variable is set when the
               file descriptor store is enabled for the service, i.e.
               _FileDescriptorStoreMax=_ is set to a non-zero value (see
               systemd.service(5) for details). Applications may check this
               environment variable before sending file descriptors to the
               service manager via sd_pid_notify_with_fds(3).
    
               Added in version 254.
    
           _$DEBUG_INVOCATION_
               If _RestartMode=debug_ is set, and a previous attempt at
               starting the unit failed, this variable will be passed to the
               service to indicate that additional logging should be enabled
               at startup. See systemd.service(5) for more details.
    
               Added in version 257.
    
           For system services, when _PAMName=_ is enabled and **pam_systemd** is
           part of the selected PAM stack, additional environment variables
           defined by systemd may be set for services. Specifically, these
           are _$XDG_SEAT_ , _$XDG_VTNR_ , see pam_systemd(8) for details.
    


## PROCESS EXIT CODES



           When invoking a unit process the service manager possibly fails to
           apply the execution parameters configured with the settings above.
           In that case the already created service process will exit with a
           non-zero exit code before the configured command line is executed.
           (Or in other words, the child process possibly exits with these
           error codes, after having been created by the fork(2) system call,
           but before the matching execve(2) system call is called.)
           Specifically, exit codes defined by the C library, by the LSB
           specification and by the systemd service manager itself are used.
    
           The following basic service exit codes are defined by the C
           library.
    
           **Table 8. Basic C library exit codes**
           ┌───────────┬───────────────┬────────────────────┐
           │ **Exit Code** │ **Symbolic Name** │ **Description** │
           ├───────────┼───────────────┼────────────────────┤
           │ 0         │ **EXIT_SUCCESS** │ Generic success    │
           │           │               │ code.              │
           ├───────────┼───────────────┼────────────────────┤
           │ 1         │ **EXIT_FAILURE** │ Generic failure or │
           │           │               │ unspecified error. │
           └───────────┴───────────────┴────────────────────┘
    
           The following service exit codes are defined by the **LSB**
           **specification******[26].**Table 9. LSB service exit codes**
           ┌───────────┬──────────────────────┬────────────────────┐
           │ **Exit Code** │ **Symbolic Name** │ **Description** │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 2         │ **EXIT_INVALIDARGUMENT** │ Invalid or excess  │
           │           │                      │ arguments.         │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 3         │ **EXIT_NOTIMPLEMENTED** │ Unimplemented      │
           │           │                      │ feature.           │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 4         │ **EXIT_NOPERMISSION** │ The user has       │
           │           │                      │ insufficient       │
           │           │                      │ privileges.        │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 5         │ **EXIT_NOTINSTALLED** │ The program is not │
           │           │                      │ installed.         │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 6         │ **EXIT_NOTCONFIGURED** │ The program is not │
           │           │                      │ configured.        │
           ├───────────┼──────────────────────┼────────────────────┤
           │ 7         │ **EXIT_NOTRUNNING** │ The program is not │
           │           │                      │ running.           │
           └───────────┴──────────────────────┴────────────────────┘
    
           The LSB specification suggests that error codes 200 and above are
           reserved for implementations. Some of them are used by the service
           manager to indicate problems during process invocation:
    
           **Table 10. systemd-specific exit codes**
           ┌───────────┬──────────────────────────────┬─────────────────────────────────────────────┐
           │ **Exit Code** │ **Symbolic Name** │ **Description** │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 200       │ **EXIT_CHDIR** │ Changing to the                             │
           │           │                              │ requested working                           │
           │           │                              │ directory failed.                           │
           │           │                              │ See                                         │
           │           │                              │ _WorkingDirectory=_                           │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 201       │ **EXIT_NICE** │ Failed to set up                            │
           │           │                              │ process scheduling                          │
           │           │                              │ priority (nice                              │
           │           │                              │ level). See _Nice=_                           │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 202       │ **EXIT_FDS** │ Failed to close                             │
           │           │                              │ unwanted file                               │
           │           │                              │ descriptors, or to                          │
           │           │                              │ adjust passed file                          │
           │           │                              │ descriptors.                                │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 203       │ **EXIT_EXEC** │ The actual process                          │
           │           │                              │ execution failed                            │
           │           │                              │ (specifically, the                          │
           │           │                              │ execve(2) system                            │
           │           │                              │ call). Most likely                          │
           │           │                              │ this is caused by                           │
           │           │                              │ a missing or                                │
           │           │                              │ non-accessible                              │
           │           │                              │ executable file.                            │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 204       │ **EXIT_MEMORY** │ Failed to perform                           │
           │           │                              │ an action due to                            │
           │           │                              │ memory shortage.                            │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 205       │ **EXIT_LIMITS** │ Failed to adjust                            │
           │           │                              │ resource limits.                            │
           │           │                              │ See _LimitCPU=_ and                           │
           │           │                              │ related settings                            │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 206       │ **EXIT_OOM_ADJUST** │ Failed to adjust                            │
           │           │                              │ the OOM setting.                            │
           │           │                              │ See                                         │
           │           │                              │ _OOMScoreAdjust=_                             │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 207       │ **EXIT_SIGNAL_MASK** │ Failed to set                               │
           │           │                              │ process signal                              │
           │           │                              │ mask.                                       │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 208       │ **EXIT_STDIN** │ Failed to set up                            │
           │           │                              │ standard input.                             │
           │           │                              │ See _StandardInput=_                          │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 209       │ **EXIT_STDOUT** │ Failed to set up                            │
           │           │                              │ standard output.                            │
           │           │                              │ See                                         │
           │           │                              │ _StandardOutput=_                             │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 210       │ **EXIT_CHROOT** │ Failed to change                            │
           │           │                              │ root directory (‐                           │
           │           │                              │ chroot(2)). See                             │
           │           │                              │ _RootDirectory=_ /_RootImage=_                   │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 211       │ **EXIT_IOPRIO** │ Failed to set up IO                         │
           │           │                              │ scheduling priority. See                    │
           │           │                              │ _IOSchedulingClass=_ /_IOSchedulingPriority=_    │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 212       │ **EXIT_TIMERSLACK** │ Failed to set up timer slack. See           │
           │           │                              │ _TimerSlackNSec=_ above.                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 213       │ **EXIT_SECUREBITS** │ Failed to set process secure bits. See      │
           │           │                              │ _SecureBits=_ above.                          │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 214       │ **EXIT_SETSCHEDULER** │ Failed to set up CPU scheduling. See        │
           │           │                              │ _CPUSchedulingPolicy=_ /_CPUSchedulingPriority=_ │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 215       │ **EXIT_CPUAFFINITY** │ Failed to set up CPU affinity. See          │
           │           │                              │ _CPUAffinity=_ above.                         │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 216       │ **EXIT_GROUP** │ Failed to determine or change group         │
           │           │                              │ credentials. See                            │
           │           │                              │ _Group=_ /_SupplementaryGroups=_ above.          │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 217       │ **EXIT_USER** │ Failed to determine or change user          │
           │           │                              │ credentials, or to set up user namespacing. │
           │           │                              │ See _User=_ /_PrivateUsers=_ above.              │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 218       │ **EXIT_CAPABILITIES** │ Failed to drop capabilities, or apply       │
           │           │                              │ ambient capabilities. See                   │
           │           │                              │ _CapabilityBoundingSet=_ /_AmbientCapabilities=_ │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 219       │ **EXIT_CGROUP** │ Setting up the service control group        │
           │           │                              │ failed.                                     │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 220       │ **EXIT_SETSID** │ Failed to create new process session.       │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 221       │ **EXIT_CONFIRM** │ Execution has been cancelled by the user.   │
           │           │                              │ See the _systemd.confirm_spawn=_ kernel       │
           │           │                              │ command line setting on                     │
           │           │                              │ kernel-command-line(7) for details.         │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 222       │ **EXIT_STDERR** │ Failed to set up standard error output. See │
           │           │                              │ _StandardError=_ above.                       │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 224       │ **EXIT_PAM** │ Failed to set up PAM session. See _PAMName=_  │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 225       │ **EXIT_NETWORK** │ Failed to set up network namespacing. See   │
           │           │                              │ _PrivateNetwork=_ above.                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 226       │ **EXIT_NAMESPACE** │ Failed to set up mount, UTS, or IPC         │
           │           │                              │ namespacing. See _ReadOnlyPaths=_ ,            │
           │           │                              │ _ProtectHostname=_ , _PrivateIPC=_ , and related  │
           │           │                              │ settings above.                             │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 227       │ **EXIT_NO_NEW_PRIVILEGES** │ Failed to disable new privileges. See       │
           │           │                              │ _NoNewPrivileges=yes_ above.                  │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 228       │ **EXIT_SECCOMP** │ Failed to apply system call filters. See    │
           │           │                              │ _SystemCallFilter=_ and related settings      │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 229       │ **EXIT_SELINUX_CONTEXT** │ Determining or changing SELinux context     │
           │           │                              │ failed. See _SELinuxContext=_ above.          │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 230       │ **EXIT_PERSONALITY** │ Failed to set up an execution domain        │
           │           │                              │ (personality). See _Personality=_ above.      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 231       │ **EXIT_APPARMOR_PROFILE** │ Failed to prepare changing AppArmor         │
           │           │                              │ profile. See _AppArmorProfile=_ above.        │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 232       │ **EXIT_ADDRESS_FAMILIES** │ Failed to restrict address families. See    │
           │           │                              │ _RestrictAddressFamilies=_ above.             │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 233       │ **EXIT_RUNTIME_DIRECTORY** │ Setting up runtime directory failed. See    │
           │           │                              │ _RuntimeDirectory=_ and related settings      │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 235       │ **EXIT_CHOWN** │ Failed to adjust socket ownership. Used for │
           │           │                              │ socket units only.                          │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 236       │ **EXIT_SMACK_PROCESS_LABEL** │ Failed to set SMACK label. See              │
           │           │                              │ _SmackProcessLabel=_ above.                   │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 237       │ **EXIT_KEYRING** │ Failed to set up kernel keyring.            │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 238       │ **EXIT_STATE_DIRECTORY** │ Failed to set up unit's state directory.    │
           │           │                              │ See _StateDirectory=_ above.                  │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 239       │ **EXIT_CACHE_DIRECTORY** │ Failed to set up unit's cache directory.    │
           │           │                              │ See _CacheDirectory=_ above.                  │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 240       │ **EXIT_LOGS_DIRECTORY** │ Failed to set up unit's logging directory.  │
           │           │                              │ See _LogsDirectory=_ above.                   │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 241       │ **EXIT_CONFIGURATION_DIRECTORY** │ Failed to set up unit's configuration       │
           │           │                              │ directory. See _ConfigurationDirectory=_      │
           │           │                              │ above.                                      │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 242       │ **EXIT_NUMA_POLICY** │ Failed to set up unit's NUMA memory policy. │
           │           │                              │ See _NUMAPolicy=_ and _NUMAMask=_ above.        │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 243       │ **EXIT_CREDENTIALS** │ Failed to set up unit's credentials. See    │
           │           │                              │ _ImportCredential=_ , _LoadCredential=_ and      │
           │           │                              │ _SetCredential=_ above.                       │
           ├───────────┼──────────────────────────────┼─────────────────────────────────────────────┤
           │ 245       │ **EXIT_BPF** │ Failed to apply BPF restrictions. See       │
           │           │                              │ _RestrictFileSystems=_ above.                 │
           └───────────┴──────────────────────────────┴─────────────────────────────────────────────┘
    
           Finally, the BSD operating systems define a set of exit codes,
           typically defined on Linux systems too:
    
           **Table 11. BSD exit codes**
           ┌───────────┬────────────────┬────────────────────┐
           │ **Exit Code** │ **Symbolic Name** │ **Description** │
           ├───────────┼────────────────┼────────────────────┤
           │ 64        │ **EX_USAGE** │ Command line usage │
           │           │                │ error              │
           ├───────────┼────────────────┼────────────────────┤
           │ 65        │ **EX_DATAERR** │ Data format error  │
           ├───────────┼────────────────┼────────────────────┤
           │ 66        │ **EX_NOINPUT** │ Cannot open input  │
           ├───────────┼────────────────┼────────────────────┤
           │ 67        │ **EX_NOUSER** │ Addressee unknown  │
           ├───────────┼────────────────┼────────────────────┤
           │ 68        │ **EX_NOHOST** │ Host name unknown  │
           ├───────────┼────────────────┼────────────────────┤
           │ 69        │ **EX_UNAVAILABLE** │ Service            │
           │           │                │ unavailable        │
           ├───────────┼────────────────┼────────────────────┤
           │ 70        │ **EX_SOFTWARE** │ internal software  │
           │           │                │ error              │
           ├───────────┼────────────────┼────────────────────┤
           │ 71        │ **EX_OSERR** │ System error       │
           │           │                │ (e.g., cannot      │
           │           │                │ fork)              │
           ├───────────┼────────────────┼────────────────────┤
           │ 72        │ **EX_OSFILE** │ Critical OS file   │
           │           │                │ missing            │
           ├───────────┼────────────────┼────────────────────┤
           │ 73        │ **EX_CANTCREAT** │ Cannot create      │
           │           │                │ (user) output file │
           ├───────────┼────────────────┼────────────────────┤
           │ 74        │ **EX_IOERR** │ Input/output error │
           ├───────────┼────────────────┼────────────────────┤
           │ 75        │ **EX_TEMPFAIL** │ Temporary failure; │
           │           │                │ user is invited to │
           │           │                │ retry              │
           ├───────────┼────────────────┼────────────────────┤
           │ 76        │ **EX_PROTOCOL** │ Remote error in    │
           │           │                │ protocol           │
           ├───────────┼────────────────┼────────────────────┤
           │ 77        │ **EX_NOPERM** │ Permission denied  │
           ├───────────┼────────────────┼────────────────────┤
           │ 78        │ **EX_CONFIG** │ Configuration      │
           │           │                │ error              │
           └───────────┴────────────────┴────────────────────┘
    


## EXAMPLES



           **Example 3.**_$MONITOR_*_ usage
    
           A service myfailer.service which can trigger an _OnFailure=_
           dependency.
    
               [Unit]
               Description=Service which can trigger an OnFailure= dependency
               OnFailure=myhandler.service
    
               [Service]
               ExecStart=/bin/myprogram
    
           A service mysuccess.service which can trigger an _OnSuccess=_
           dependency.
    
               [Unit]
               Description=Service which can trigger an OnSuccess= dependency
               OnSuccess=myhandler.service
    
               [Service]
               ExecStart=/bin/mysecondprogram
    
           A service myhandler.service which can be triggered by any of the
           above services.
    
               [Unit]
               Description=Acts on service failing or succeeding
    
               [Service]
               ExecStart=/bin/bash -c "echo $MONITOR_SERVICE_RESULT $MONITOR_EXIT_CODE $MONITOR_EXIT_STATUS $MONITOR_INVOCATION_ID $MONITOR_UNIT"
    
           If myfailer.service were to run and exit in failure, then
           myhandler.service would be triggered and the monitor variables
           would be set as follows:
    
               MONITOR_SERVICE_RESULT=exit-code
               MONITOR_EXIT_CODE=exited
               MONITOR_EXIT_STATUS=1
               MONITOR_INVOCATION_ID=cc8fdc149b2b4ca698d4f259f4054236
               MONITOR_UNIT=myfailer.service
    
           If mysuccess.service were to run and exit in success, then
           myhandler.service would be triggered and the monitor variables
           would be set as follows:
    
               MONITOR_SERVICE_RESULT=success
               MONITOR_EXIT_CODE=exited
               MONITOR_EXIT_STATUS=0
               MONITOR_INVOCATION_ID=6ab9af147b8c4a3ebe36e7a5f8611697
               MONITOR_UNIT=mysuccess.service
    


## NOTES



            1. Discoverable Partitions Specification
               https://uapi-group.org/specifications/specs/discoverable_partitions_specification
    
            2. The /proc Filesystem
               https://docs.kernel.org/filesystems/proc.html#mount-options
    
            3. User/Group Name Syntax
               https://systemd.io/USER_NAMES
    
            4. Password Agent
               https://systemd.io/PASSWORD_AGENTS
    
            5. No New Privileges Flag
               https://docs.kernel.org/userspace-api/no_new_privs.html
    
            6. JSON User Record
               https://systemd.io/USER_RECORD
    
            7. The /proc Filesystem
               https://docs.kernel.org/filesystems/proc.html
    
            8. id-mapped mounts
               https://lwn.net/Articles/896255/
    
            9. quotactl
               https://man7.org/linux/man-pages/man2/quotactl.2.html
    
           10. quotaon.
               https://linux.die.net/man/8/quotaon
    
           11. repquota
               https://man7.org/linux/man-pages/man8/repquota.8.html
    
           12. Kernel Samepage Merging
               https://docs.kernel.org/admin-guide/mm/ksm.html
    
           13. LWN post
               https://lwn.net/Articles/947173/
    
           14. unicode scalar values
               https://www.unicode.org/glossary/#unicode_scalar_value
    
           15. unicode noncharacters
               https://www.unicode.org/glossary/#noncharacter
    
           16. unicode byte order mark
               https://www.unicode.org/glossary/#byte_order_mark
    
           17. POSIX shell unquoted text
               https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_01
    
           18. POSIX shell single-quoted text
               https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_02
    
           19. POSIX shell double-quoted text
               https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_02_03
    
           20. Base64
               https://tools.ietf.org/html/rfc2045#section-6.8
    
           21. Container Interface
               https://systemd.io/CONTAINER_INTERFACE
    
           22. DMI/SMBIOS
               https://www.dmtf.org/standards/smbios
    
           23. qemu
               https://www.qemu.org/docs/master/system/index.html
    
           24. System and Service Credentials
               https://systemd.io/CREDENTIALS
    
           25. Memory Pressure Handling
               https://systemd.io/MEMORY_PRESSURE
    
           26. LSB specification
               https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html
    


* * *