# udevadm

## NAME



           udevadm - udev management tool
    


## SYNOPSIS



    
           **udevadm**[**--debug**] [**--version**] [**--help**]
    
           **udevadm info**[_options_...] [_devpath_ |_syspath_ |_id_ |_unit_...]
    
           **udevadm trigger**[_options_...] [_devpath_ |_syspath_ |_id_ |_unit_...]
    
           **udevadm settle**[_options_...]
    
           **udevadm control** _options_...
    
           **udevadm monitor**[_options_...]
    
           **udevadm test**[_options_...] _devpath_ |_syspath_ |_id_ |_unit_
    
           **udevadm test-builtin**[_options_...] _command devpath_ |_syspath_ |_id_ |_unit_
    
           **udevadm verify**[_options_...] [_files_...]
    
           **udevadm cat**[_options_...] [_files_...]
    
           **udevadm wait**[_options_...] _devpath_ |_syspath_...
    
           **udevadm lock**[_options_...] _command_...
    


## DESCRIPTION



           **udevadm** expects a command and command specific options. It
           controls the runtime behavior of **systemd-udevd** , requests kernel
           events, manages the event queue, and provides simple debugging
           mechanisms.
    


## OPTIONS



           **-d** , **--debug**
               Print debug messages to standard error. This option is implied
               in **udevadm test** and **udevadm test-builtin** commands.
    
           **-V** , **--version**
               Print a short version string and exit.
    
           **-h** , **--help**
               Print a short help text and exit.
    
       **udevadm info [_options_**...] [_**devpath**_ |_**syspath**_ |_**id**_ |_**unit**_...]
           Query the udev database for device information.
    
           Positional arguments should be used to specify one or more
           devices. Each one may be a device name (in which case it must
           start with /dev/), a sys path (in which case it must start with
           /sys/), a device ID (such as "n1", "c5:1", or "b259:1", see
           sd_device_get_device_id(3)). or a systemd device unit name (in
           which case it must end with ".device", see systemd.device(5)).
    
           **-q** , **--query=**_TYPE_
               Query the database for the specified type of device data.
               Valid _TYPE_ s are: **name** , **symlink** , **path** , **property** , **all**.
    
           **--property=**_NAME_
               When showing device properties using the **--query=property**
               option, limit display to properties specified in the argument.
               The argument should be a comma-separated list of property
               names. If not specified, all known properties are shown.
    
               Added in version 250.
    
           **--value**
               When showing device properties using the **--query=property**
               option, print only their values, and skip the property name
               and "=".
    
               Cannot be used together with **-x/--export** or
               **-P/--export-prefix**.
    
               Added in version 250.
    
           **-p** , **--path=**_DEVPATH_
               The /sys/ path of the device to query, e.g.
               [/sys/]/class/block/sda. This option is an alternative to the
               positional argument with a /sys/ prefix.  **udevadm info**
               **--path=/class/block/sda** is equivalent to **udevadm info**
               **/sys/class/block/sda**.
    
           **-n** , **--name=**_FILE_
               The name of the device node or a symlink to query, e.g.
               [/dev/]/sda. This option is an alternative to the positional
               argument with a /dev/ prefix.  **udevadm info --name=sda** is
               equivalent to **udevadm info /dev/sda**.
    
           **-r** , **--root**
               Print absolute paths in **name** or **symlink** query.
    
           **-a** , **--attribute-walk**
               Print all sysfs properties of the specified device that can be
               used in udev rules to match the specified device. It prints
               all devices along the chain, up to the root of sysfs that can
               be used in udev rules.
    
               This switch supports JSON output mode (see **--json=** below).
               Note that because this switch generates multiple JSON objects,
               JSON-SEQ mode is automatically enabled (RFC7464). (Note: tools
               such as **jq******[1] natively support JSON-SEQ via the**--seq** switch.)
    
           **-t** , **--tree**
               Display a sysfs tree. This recursively iterates through the
               sysfs hierarchy and displays it in a tree structure. If a path
               is specified only the subtree below and its parent directories
               are shown. This will show both device and subsystem items.
    
               Added in version 251.
    
           **-x** , **--export**
               Print output as key/value pairs. Values are enclosed in single
               quotes. This takes effects only when **--query=property** or
               **--device-id-of-file=**_FILE_ is specified.
    
           **-P** , **--export-prefix=**_NAME_
               Add a prefix to the key name of exported values. This implies
               **--export**.
    
           **-d** , **--device-id-of-file=**_FILE_
               Print major/minor numbers of the underlying device, where the
               file lives on. If this is specified, all positional arguments
               are ignored.
    
           **-e** , **--export-db**
               Export the content of the udev database.
    
           **-c** , **--cleanup-db**
               Cleanup the udev database.
    
           **-w[SECONDS]** , **--wait-for-initialization[=SECONDS]**
               Wait for device to be initialized. If argument _SECONDS_ is not
               specified, the default is to wait forever.
    
               Added in version 243.
    
           **--subsystem-match[=SUBSYSTEM]** , **--subsystem-nomatch[=SUBSYSTEM]**
               When used with **--export-db** , only show devices of or not of the
               given subsystem respectively.
    
               Added in version 255.
    
           **--attr-match[=FILE[=VALUE]]** , **--attr-nomatch[=FILE[=VALUE]]**
               When used with **--export-db** , only show devices matching or not
               matching the given attribute respectively.
    
               Added in version 255.
    
           **--property-match[=KEY=VALUE]**
               When used with **--export-db** , only show devices matching the
               given property and value.
    
               Added in version 255.
    
           **--tag-match[=TAG]**
               When used with **--export-db** , only show devices with the given
               tag.
    
               Added in version 255.
    
           **--sysname-match[=NAME]**
               When used with **--export-db** , only show devices with the given
               "/sys" path.
    
               Added in version 255.
    
           **--name-match[=NAME]**
               When used with **--export-db** , only show devices with the given
               name in "/dev".
    
               Added in version 255.
    
           **--parent-match[=NAME]**
               When used with **--export-db** , only show devices with the given
               parent device.
    
               Added in version 255.
    
           **--initialized-match** , **--initialized-nomatch**
               When used with **--export-db** , only show devices that are
               initialized or not initialized respectively.
    
               Added in version 255.
    
           **--json=**_MODE_
               Shows output formatted as JSON. Expects one of "short" (for
               the shortest possible output without any redundant whitespace
               or line breaks), "pretty" (for a pretty version of the same,
               with indentation and line breaks) or "off" (to turn off JSON
               output, the default).
    
           **--no-pager**
               Do not pipe output into a pager.
    
           The generated output shows the current device database entry in a
           terse format. Each line shown is prefixed with one of the
           following characters:
    
           **Table 1. udevadm info output prefixes**
           ┌────────┬──────────────────────────┐
           │ **Prefix** │ **Meaning** │
           ├────────┼──────────────────────────┤
           │ "P:"   │ Device path in /sys/     │
           ├────────┼──────────────────────────┤
           │ "M:"   │ Device name in /sys/     │
           │        │ (i.e. the last component │
           │        │ of "P:")                 │
           ├────────┼──────────────────────────┤
           │ "R:"   │ Device number in /sys/   │
           │        │ (i.e. the numeric suffix │
           │        │ of the last component of │
           │        │ "P:")                    │
           ├────────┼──────────────────────────┤
           │ "J:"   │ Device ID                │
           ├────────┼──────────────────────────┤
           │ "U:"   │ Kernel subsystem         │
           ├────────┼──────────────────────────┤
           │ "B:"   │ Driver subsystem         │
           ├────────┼──────────────────────────┤
           │ "T:"   │ Kernel device type       │
           │        │ within subsystem         │
           ├────────┼──────────────────────────┤
           │ "D:"   │ Kernel device node       │
           │        │ major/minor              │
           ├────────┼──────────────────────────┤
           │ "I:"   │ Network interface index  │
           ├────────┼──────────────────────────┤
           │ "N:"   │ Kernel device node name  │
           ├────────┼──────────────────────────┤
           │ "L:"   │ Device node symlink      │
           │        │ priority                 │
           ├────────┼──────────────────────────┤
           │ "S:"   │ Device node symlink      │
           ├────────┼──────────────────────────┤
           │ "Q:"   │ Block device sequence    │
           │        │ number (DISKSEQ)         │
           ├────────┼──────────────────────────┤
           │ "V:"   │ Attached driver          │
           ├────────┼──────────────────────────┤
           │ "E:"   │ Device property          │
           └────────┴──────────────────────────┘
    
       **udevadm trigger [_options_**...] [_**devpath**_ |_**syspath**_ |_**id**_ |_**unit**_...]
           Request device events from the kernel. Primarily used to replay
           events at system coldplug time.
    
           Takes device specifications as positional arguments. See the
           description of **udevadm info** above.
    
           **-v** , **--verbose**
               Print the list of devices which will be triggered.
    
           **-n** , **--dry-run**
               Do not actually trigger the event.
    
           **-q** , **--quiet**
               Suppress error logging in triggering events.
    
               Added in version 248.
    
           **-t** , **--type=**_TYPE_
               Trigger a specific type of devices. Valid types are "all",
               "devices", and "subsystems". The default value is "devices".
    
           **-c** , **--action=**_ACTION_
               Type of event to be triggered. Possible actions are "add",
               "remove", "change", "move", "online", "offline", "bind", and
               "unbind". Also, the special value "help" can be used to list
               the possible actions. The default value is "change".
    
           **--prioritized-subsystem=**_SUBSYSTEM[,SUBSYSTEM_...]
               Takes a comma separated list of subsystems. When triggering
               events for devices, the devices from the specified subsystems
               and their parents are triggered first. For example, if
               **--prioritized-subsystem=block,net** , then firstly all block
               devices and their parents are triggered, in the next all
               network devices and their parents are triggered, and lastly
               the other devices are triggered. This option can be specified
               multiple times, and in that case the lists of the subsystems
               will be merged. That is, **--prioritized-subsystem=block**
               **--prioritized-subsystem=net** is equivalent to
               **--prioritized-subsystem=block,net**.
    
               Added in version 251.
    
           **-s** , **--subsystem-match=**_SUBSYSTEM_
               Trigger events for devices which belong to a matching
               subsystem. This option supports shell style pattern matching.
               When this option is specified more than once, then each
               matching result is ORed, that is, all the devices in each
               subsystem are triggered.
    
           **-S** , **--subsystem-nomatch=**_SUBSYSTEM_
               Do not trigger events for devices which belong to a matching
               subsystem. This option supports shell style pattern matching.
               When this option is specified more than once, then each
               matching result is ANDed, that is, devices which do not match
               all specified subsystems are triggered.
    
           **-a** , **--attr-match=**_ATTRIBUTE_**=**_VALUE_
               Trigger events for devices with a matching sysfs attribute. If
               a value is specified along with the attribute name, the
               content of the attribute is matched against the given value
               using shell style pattern matching. If no value is specified,
               the existence of the sysfs attribute is checked. When this
               option is specified multiple times, then each matching result
               is ANDed, that is, only devices which have all specified
               attributes are triggered.
    
           **-A** , **--attr-nomatch=**_ATTRIBUTE_**=**_VALUE_
               Do not trigger events for devices with a matching sysfs
               attribute. If a value is specified along with the attribute
               name, the content of the attribute is matched against the
               given value using shell style pattern matching. If no value is
               specified, the existence of the sysfs attribute is checked.
               When this option is specified multiple times, then each
               matching result is ANDed, that is, only devices which have
               none of the specified attributes are triggered.
    
           **-p** , **--property-match=**_PROPERTY_**=**_VALUE_
               Trigger events for devices with a matching property value.
               This option supports shell style pattern matching. When this
               option is specified more than once, then each matching result
               is ORed, that is, devices which have one of the specified
               properties are triggered.
    
           **-g** , **--tag-match=**_TAG_
               Trigger events for devices with a matching tag. When this
               option is specified multiple times, then each matching result
               is ANDed, that is, devices which have all specified tags are
               triggered.
    
           **-y** , **--sysname-match=**_NAME_
               Trigger events for devices for which the last component (i.e.
               the filename) of the /sys/ path matches the specified _PATH_.
               This option supports shell style pattern matching. When this
               option is specified more than once, then each matching result
               is ORed, that is, all devices which have any of the specified
               _NAME_ are triggered.
    
           **--name-match=**_NAME_
               Trigger events for devices with a matching device path. When
               this option is specified more than once, then each matching
               result is ORed, that is, all specified devices are triggered.
    
               Added in version 218.
    
           **-b** , **--parent-match=**_SYSPATH_
               Trigger events for all children of a given device. When this
               option is specified more than once, then each matching result
               is ORed, that is, all children of each specified device are
               triggered.
    
           **--initialized-match** , **--initialized-nomatch**
               When **--initialized-match** is specified, trigger events for
               devices that are already initialized by **systemd-udevd** , and
               skip devices that are not initialized yet.
    
               When **--initialized-nomatch** is specified, trigger events for
               devices that are not initialized by **systemd-udevd** yet, and
               skip devices that are already initialized.
    
               Typically, it is essential that applications which intend to
               use such a match, make sure a suitable udev rule is installed
               that sets at least one property on devices that shall be
               matched. See also Initialized Devices section below for more
               details.
    
                   **Warning**
                   **--initialized-nomatch** can potentially save a significant
                   amount of time compared to re-triggering all devices in
                   the system and e.g. can be used to optimize boot time.
                   However, this is not safe to be used in a boot sequence in
                   general. Especially, when udev rules for a device depend
                   on its parent devices (e.g.  "ATTRS" or "IMPORT{parent}"
                   keys, see udev(7) for more details), the final state of
                   the device becomes easily unstable with this option.
               Added in version 251.
    
           **--include-parents**
               Trigger parent devices of found devices even if the parents
               will not match the filter condition. This is useful if we are
               interested to limit the coldplug activities to some devices or
               subsystems.
    
               Added in version 258.
    
           **-w** , **--settle**
               Apart from triggering events, also waits for those events to
               finish. Note that this is different from calling **udevadm**
               **settle**.  **udevadm settle** waits for all events to finish. This
               option only waits for events triggered by the same command to
               finish.
    
               Added in version 238.
    
           **--uuid**
               Trigger the synthetic device events, and associate a
               randomized UUID with each. These UUIDs are printed to standard
               output, one line for each event. These UUIDs are included in
               the uevent environment block (in the "SYNTH_UUID=" property)
               and may be used to track delivery of the generated events.
    
               Added in version 249.
    
           **--wait-daemon[=**_SECONDS_**]**
               Before triggering uevents, wait for systemd-udevd daemon to be
               initialized. Optionally takes timeout value. Default timeout
               is 5 seconds. This is equivalent to invoking **udevadm control**
               **--ping** before **udevadm trigger**.
    
               Added in version 241.
    
           In addition, optional positional arguments can be used to specify
           device names or sys paths. They must start with /dev/ or /sys/
           respectively.
    
       **udevadm settle [_options_**...]
           Watches the udev event queue, and exits if all current events are
           handled.
    
           **-t** , **--timeout=**_SECONDS_
               Maximum number of seconds to wait for the event queue to
               become empty. The default value is 120 seconds. A value of 0
               will check if the queue is empty and always return
               immediately. A non-zero value will return an exit code of 0 if
               queue became empty before timeout was reached, non-zero
               otherwise.
    
           **-E** , **--exit-if-exists=**_FILE_
               Stop waiting if file exists.
    
           See systemd-udev-settle.service(8) for more information.
    
       **udevadm control _options_**...
           Modify the internal state of the running udev daemon.
    
           **-e** , **--exit**
               Signal and wait for systemd-udevd to exit. No option except
               for **--timeout** can be specified after this option. Note that
               systemd-udevd.service contains **Restart=always** and so as a
               result, this option restarts systemd-udevd. If you want to
               stop systemd-udevd.service, please use the following:
    
                   systemctl stop systemd-udevd-control.socket systemd-udevd-kernel.socket systemd-udevd-varlink.socket systemd-udevd.service
    
           **-l** , **--log-level=**_value_
               Set the internal log level of systemd-udevd. Valid values are
               the numerical syslog priorities or their textual
               representations: **emerg** , **alert** , **crit** , **err** , **warning** , **notice** ,
               **info** , and **debug**.
    
           **-s** , **--stop-exec-queue**
               Signal systemd-udevd to stop executing new events. Incoming
               events will be queued.
    
           **-S** , **--start-exec-queue**
               Signal systemd-udevd to enable the execution of events.
    
           **-R** , **--reload**
               Signal systemd-udevd to reload the rules files and other
               databases like the kernel module index. Reloading rules and
               databases does not apply any changes to already existing
               devices; the new configuration will only be applied to new
               events.
    
           **-p** , **--property=**_KEY_**=**_value_
               Set a global property for all events.
    
           **-m** , **--children-max=**_value_
               Set the maximum number of events, systemd-udevd will handle at
               the same time. When 0 is specified, then the maximum is
               determined based on the system resources.
    
           **--ping**
               Send a ping message to systemd-udevd and wait for the reply.
               This may be useful to check that systemd-udevd daemon is
               running.
    
               Added in version 241.
    
           **--trace=**_BOOL_
               Enable/disable trace logging in **systemd-udevd**.
    
               Added in version 258.
    
           **--revert**
               Revert settings previously set with **udevadm control** command.
               When specified, settings set with **-l/--log-level=** , **--trace** ,
               **-m/--children-max=** , and **-p/--property=** will be cleared.
    
               Added in version 258.
    
           **-t** , **--timeout=**_seconds_
               The maximum number of seconds to wait for a reply from
               systemd-udevd.
    
           **--load-credentials**
               When specified, the following credentials are used when passed
               in:
    
               _udev.conf.*_
                   These credentials should contain valid udev.conf(5)
                   configuration data. From each matching credential a
                   separate file is created. Example: a passed credential
                   udev.conf.50-foobar will be copied into a configuration
                   file /run/udev/udev.conf.d/50-foobar.conf.
    
                   Added in version 256.
    
               _udev.rules.*_
                   These credentials should contain valid udev(7) rules. From
                   each matching credential a separate file is created.
                   Example: a passed credential udev.rules.50-foobar will be
                   copied into a configuration file
                   /run/udev/rules.d/50-foobar.rules.
    
                   Added in version 256.
    
               Note, this _does not_ imply **--reload** option. So, if
               **systemd-udevd** is already running, please consider to also
               specify **-reload** to make the copied udev rules files used by
               **systemd-udevd**.
    
               Added in version 256.
    
       **udevadm monitor [_options_**...]
           Listens to the kernel uevents and events sent out by a udev rule
           and prints the devpath of the event to the console. It can be used
           to analyze the event timing, by comparing the timestamps of the
           kernel uevent and the udev event.
    
           **-k** , **--kernel**
               Print the kernel uevents.
    
           **-u** , **--udev**
               Print the udev event after the rule processing.
    
           **-p** , **--property**
               Also print the properties of the event.
    
           **-s** , **--subsystem-match=**_string[/string]_
               Filter kernel uevents and udev events by subsystem[/devtype].
               Only events with a matching subsystem value will pass. When
               this option is specified more than once, then each matching
               result is ORed, that is, all devices in the specified
               subsystems are monitored.
    
           **-t** , **--tag-match=**_string_
               Filter udev events by tag. Only udev events with a given tag
               attached will pass. When this option is specified more than
               once, then each matching result is ORed, that is, devices
               which have one of the specified tags are monitored.
    
       **udevadm test [_options_**...] _**devpath**_ |_**syspath**_ |_**id**_ |**unit**
           Simulate a udev event run for the given device, and print debug
           output. The option **--json=** may be useful for parsing the final
           result. See also Example section.
    
           **-a** , **--action=**_ACTION_
               Type of event to be simulated. Possible actions are "add",
               "remove", "change", "move", "online", "offline", "bind", and
               "unbind". Also, the special value "help" can be used to list
               the possible actions. The default value is "add".
    
           **-N** , **--resolve-names=early|late|never**
               Specify when **udevadm** should resolve names of users and groups
               specified in udev rules. When set to **early**(the default),
               names will be resolved when the rules are parsed. When set to
               **late** , names will be resolved during the event being processed.
               When set to **never** , names will never be resolved and relevant
               udev rules will be ignored.
    
               Added in version 209.
    
           **-D** _DIR_ , **--extra-rules-dir=**_DIR_
               Also load udev rules files from the specified directory. This
               option can be specified multiple times. It may be useful for
               debugging udev rules by copying some udev rules files to a
               temporary directory, editing them, and specifying the
               directory with this option. Files found in the specified
               directories have a higher priority than rules files in the
               default udev/rules.d directories used by **systemd-udevd**. See
               udev(7) for more details about the search paths.
    
               Added in version 258.
    
           **-v** , **--verbose**
               Shows verbose logs in processing udev rules.
    
               Added in version 258.
    
           **--json=**_MODE_
               Shows output formatted as JSON. Expects one of "short" (for
               the shortest possible output without any redundant whitespace
               or line breaks), "pretty" (for a pretty version of the same,
               with indentation and line breaks) or "off" (to turn off JSON
               output, the default).
    
       **udevadm test-builtin [_options_**...] _**command devpath**_ |_**file**_ |**unit**
           Run a built-in command _COMMAND_ for device _DEVPATH_ , and print debug
           output.
    
           **-a** , **--action=**_ACTION_
               Type of event to be simulated. Possible actions are "add",
               "remove", "change", "move", "online", "offline", "bind", and
               "unbind". Also, the special value "help" can be used to list
               the possible actions. The default value is "add".
    
               Added in version 250.
    
       **udevadm verify [_options_**...] [_**files**_...]
           Verify syntactic, semantic, and stylistic correctness of udev
           rules files.
    
           Positional arguments can be used to specify one or more files to
           check. Each argument must be an absolute path to a udev rules file
           or a directory that contains rules files, or a file name of udev
           rules file (e.g.  99-systemd.rules). If a file name is specified,
           the file will be searched in the udev/rules.d directories that are
           processed by **systemd-udevd** , and searched in the current working
           directory if not found. If no files are specified, the udev rules
           are read from the files located in the same udev/rules.d
           directories that are processed by **systemd-udevd**. See udev(7) for
           more details about the search paths.
    
           The exit status is **0** if all specified udev rules files are
           syntactically, semantically, and stylistically correct, and a
           non-zero error code otherwise.
    
           **-N** , **--resolve-names=early|late|never**
               Specify when **udevadm** should resolve names of users and groups
               specified in udev rules. When set to **early**(the default),
               names will be resolved when the rules are parsed. When set to
               **late** , names will not be verified, as **systemd-udevd** resolves
               names during each event being processed. When set to **never** ,
               names will never be resolved and relevant rules will be
               ignored.
    
               Added in version 254.
    
           **--root=**_PATH_
               When looking for udev rules files located in the udev/rules.d
               directories, operate on files underneath the specified root
               path _PATH_. When a file name is specified, and it is not found
               in the udev/rules.d directories, the file will be searched in
               the specified root path _PATH_ , rather than the current working
               directory.
    
               Added in version 254.
    
           **--no-summary**
               Do not show summary.
    
               Added in version 254.
    
           **--no-style**
               Ignore style issues. When specified, even if style issues are
               found in udev rules files, the exit status is **0** if no
               syntactic or semantic errors are found.
    
               Added in version 254.
    
       **udevadm cat [_options_**...] [_**file**_...]
           Show udev rules files or udev.conf.
    
           Positional arguments can be used to specify one or more files to
           show. Each argument must be an absolute path to a udev rules file
           or a directory that contains rules files, or a file name of udev
           rules file (e.g.  99-systemd.rules). If a file name is specified,
           the file will be searched in the udev/rules.d directories that are
           processed by **systemd-udevd** , and searched in the current working
           directory if not found. If no files are specified, the udev rules
           are read from the files located in the same udev/rules.d
           directories that are processed by **systemd-udevd**. See udev(7) for
           more details about the search paths.
    
           **--root=**_PATH_
               When looking for udev rules files located in the udev/rules.d
               directories, operate on files underneath the specified root
               path _PATH_. When a file name is specified, and it is not found
               in the udev/rules.d directories, the file will be searched in
               the specified root path _PATH_ , rather than the current working
               directory.
    
               Added in version 258.
    
           **--tldr**
               Only print the "interesting" parts of the configuration files,
               skipping comments and empty lines and section headers followed
               only by comments and empty lines.
    
               Added in version 258.
    
           **--config**
               Shows udev.conf(5) files, rather than udev rules files. When
               specified, no udev rules file cannot be specified.
    
               Added in version 258.
    
       **udevadm wait [_options_**...] _**devpath|syspath**_...
           Wait for devices or device symlinks being created and initialized
           by **systemd-udevd**. Each device path must start with "/dev/" or
           "/sys/", e.g.  "/dev/sda",
           "/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1",
           "/sys/devices/pci0000:00/0000:00:1f.6/net/eth0", or
           "/sys/class/net/eth0". This can take multiple devices. This may be
           useful for waiting for devices being processed by **systemd-udevd**
           after e.g. partitioning or formatting the devices.
    
           **-t** , **--timeout=**_SECONDS_
               Maximum number of seconds to wait for the specified devices or
               device symlinks being created, initialized, or removed. The
               default value is "infinity".
    
               Added in version 251.
    
           **--initialized=**_BOOL_
               Check if **systemd-udevd** initialized devices. Defaults to true.
               When false, the command only checks if the specified devices
               exist. Set false to this setting if there is no udev rules for
               the specified devices, as the devices will never be considered
               as initialized in that case. See Initialized Devices section
               below for more details.
    
               Added in version 251.
    
           **--removed**
               When specified, the command wait for devices being removed
               instead of created or initialized. If this is specified,
               **--initialized=** will be ignored.
    
               Added in version 251.
    
           **--settle**
               When specified, also watches the udev event queue, and wait
               for all queued events being processed by **systemd-udevd**.
    
               Added in version 251.
    
       **udevadm lock [_options_**...] _**command**_...
           **udevadm lock** takes an (advisory) exclusive lock on a block device
           (or all specified devices), as per **Locking Block Device Access******[2]
           and invokes a program with the locks taken. When the invoked
           program exits the locks are automatically released and its return
           value is propagated as exit code of**udevadm lock**.
    
           This tool is in particular useful to ensure that
           systemd-udevd.service(8) does not probe a block device while
           changes are made to it, for example partitions created or file
           systems formatted. Note that many tools that interface with block
           devices natively support taking relevant locks, see for example
           sfdisk(8)'s **--lock** switch.
    
           The command expects at least one block device specified via
           **--device=** or **--backing=** , and a command line to execute as
           arguments.
    
           **--device=**_DEVICE_ , **-d** _DEVICE_
               Takes a path to a device node of the device to lock. This
               switch may be used multiple times (and in combination with
               **--backing=**) in order to lock multiple devices. If a partition
               block device node is specified the containing "whole" block
               device is automatically determined and used for the lock, as
               per the specification. If multiple devices are specified, they
               are deduplicated, sorted by the major/minor of their device
               nodes and then locked in order.
    
               This switch must be used at least once, to specify at least
               one device to lock. (Alternatively, use **--backing=** , see
               below.)
    
               Added in version 251.
    
           **--backing=**_PATH_ , **-b** _PATH_
               If a path to a device node is specified, identical to
               **--device=**. However, this switch alternatively accepts a path
               to a regular file or directory, in which case the block device
               of the file system the file/directory resides on is
               automatically determined and used as if it was specified with
               **--device=**.
    
               Added in version 251.
    
           **--timeout=**_SECS_ , **-t** _SECS_
               Specifies how long to wait at most until all locks can be
               taken. Takes a value in seconds, or in the usual supported
               time units, see systemd.time(7). If specified as zero the lock
               is attempted and if not successful the invocation will
               immediately fail. If passed as "infinity" (the default) the
               invocation will wait indefinitely until the lock can be
               acquired. If the lock cannot be taken in the specified time
               the specified command will not be executed and the invocation
               will fail.
    
               Added in version 251.
    
           **--print** , **-p**
               Instead of locking the specified devices and executing a
               command, just print the device paths that would be locked, and
               execute no command. This command is useful to determine the
               "whole" block device in case a partition block device is
               specified. The devices will be sorted by their device node
               major number as primary ordering key and the minor number as
               secondary ordering key (i.e. they are shown in the order
               they'd be locked). Note that the number of lines printed here
               can be less than the number of **--device=** and **--backing=**
               switches specified in case these resolve to the same "whole"
               devices.
    
               Added in version 251.
    


## INITIALIZED DEVICES



           Initialized devices are those for which at least one udev rule
           already completed execution – for any action but "remove" — that
           set a property or other device setting (and thus has an entry in
           the udev device database). Devices are no longer considered
           initialized if a "remove" action is seen for them (which removes
           their entry in the udev device database). Note that devices that
           have no udev rules are never considered initialized, but might
           still be announced via the sd-device API (or similar).
    


## EXAMPLE



           **Example 1. Format a File System**
    
           Take a lock on the backing block device while creating a file
           system, to ensure that **systemd-udevd** does not probe or announce
           the new superblock before it is comprehensively written:
    
               # udevadm lock --device=/dev/sda1 mkfs.ext4 /dev/sda1
    
           **Example 2. Format a RAID File System**
    
           Similar, but take locks on multiple devices at once:
    
               # udevadm lock --device=/dev/sda1 --device=/dev/sdb1 mkfs.btrfs /dev/sda1 /dev/sdb1
    
           **Example 3. Copy in a File System**
    
           Take a lock on the backing block device while copying in a
           prepared file system image, to ensure that **systemd-udevd** does not
           probe or announce the new superblock before it is fully written:
    
               # udevadm lock -d /dev/sda1 dd if=fs.raw of=/dev/sda1
    
           **Example 4. Predict Network Interface Renaming**
    
           To predict a network interface name, **udevadm test** can be used:
    
               $ udevadm test /sys/class/net/wlan0 --json=pretty 2>/dev/null | jq .networkInterface.name
               "wlp59s0"
    
           **Example 5. Predict Symbolic links of a Device Node**
    
           To predict symbolic links to a device node, **udevadm test** can be
           used:
    
               $ udevadm test /dev/nvme0n1p1 --json=pretty 2>/dev/null | jq .node.symlinks
               [
                 "/dev/disk/by-diskseq/1-part1",
                 "/dev/disk/by-id/nvme-WDC_PC_SN720_SDAQNTW-512G-1001_192290802247-part1",
                 "/dev/disk/by-id/nvme-WDC_PC_SN720_SDAQNTW-512G-1001_192290802247_1-part1",
                 "/dev/disk/by-id/nvme-eui.1922908022470001001b448b44ccb9d6-part1",
                 "/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part/by-partnum/1",
                 "/dev/disk/by-path/pci-0000:3c:00.0-nvme-1-part1"
               ]
               $ udevadm test /dev/input/event3 --json=pretty 2>/dev/null | jq .node.symlinks
               [
                 "/dev/input/by-path/platform-i8042-serio-0-event-kbd"
               ]
    


## NOTES



            1. jq
               https://jqlang.github.io/jq/manual/
    
            2. Locking Block Device Access
               https://systemd.io/BLOCK_DEVICE_LOCKING
    


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