# kernel-command-line

## NAME



           kernel-command-line - Kernel command line parameters
    


## SYNOPSIS



           /proc/cmdline
    


## DESCRIPTION



           The kernel, the programs running in the initrd and in the host
           system may be configured at boot via kernel command line
           arguments.
    
           For command line parameters understood by the kernel, please see
           **kernel-parameters.html******[1] andbootparam(7).
    
           For command line parameters understood by the initrd, see the
           documentation of the specific initrd implementation of your
           installation.
    


## CORE OS COMMAND LINE ARGUMENTS



           _systemd.unit=_ , _rd.systemd.unit=_ , _systemd.dump_core_ ,
           _systemd.crash_chvt_ , _systemd.crash_shell_ , _systemd.crash_action=_ ,
           _systemd.confirm_spawn_ , _systemd.service_watchdogs_ ,
           _systemd.show_status_ , _systemd.status_unit_format=_ ,
           _systemd.log_target=_ , _systemd.log_level=_ , _systemd.log_location=_ ,
           _systemd.log_color_ , _systemd.log_ratelimit_kmsg_ ,
           _systemd.default_standard_output=_ , _systemd.default_standard_error=_ ,
           _systemd.setenv=_ , _systemd.machine_id=_ , _systemd.set_credential=_ ,
           _systemd.set_credential_binary=_ , _systemd.import_credentials=_ ,
           _systemd.reload_limit_interval_sec=_ , _systemd.reload_limit_burst=_
               Parameters understood by the system and service manager to
               control system behavior. For details, see systemd(1).
    
               Added in version 186.
    
           _systemd.mask=_ , _systemd.wants=_ , _systemd.debug_shell_ ,
           _systemd.default_debug_tty=_
               Additional parameters understood by
               systemd-debug-generator(8), to mask or start specific units at
               boot, or invoke a debug shell on tty9.
    
               Added in version 215.
    
           _systemd.break=_ , _rd.systemd.break=_
               Parameters understood by systemd-debug-generator(8), to pause
               the boot process at a certain point and spawn a debug shell.
    
               Added in version 258.
    
           _systemd.run=_ , _systemd.run_success_action=_ ,
           _systemd.run_failure_action=_
               Additional parameters understood by systemd-run-generator(8),
               to run a command line specified on the kernel command line as
               system service after booting up.
    
               Added in version 240.
    
           _systemd.early_core_pattern=_
               During early boot, the generation of core dump files is
               disabled until a core dump handler (if any) takes over. This
               parameter allows specifying an absolute path where core dump
               files should be stored until a handler is installed. The path
               should be absolute and may contain specifiers, see core(5) for
               details.
    
               Added in version 240.
    
           _systemd.restore_state=_
               This parameter is understood by several system tools to
               control whether or not they should restore system state from
               the previous boot. For details, see
               systemd-backlight@.service(8) and systemd-rfkill.service(8).
    
               Added in version 209.
    
           _systemd.ssh_auto=_ , _systemd.ssh_listen=_
               These parameters are interpreted by systemd-ssh-generator(8)
               and may be used to control SSH sockets the system shall be
               reachable on.
    
               Added in version 256.
    
           _systemd.volatile=_
               This parameter controls whether the system shall boot up in
               volatile mode. Takes a boolean argument, or the special values
               "state" or "overlay". If false (the default), normal boot mode
               is selected, the root directory and /var/ are mounted as
               specified on the kernel command line or /etc/fstab, or
               otherwise configured. If true, full state-less boot mode is
               selected. In this case, the root directory is mounted as
               volatile memory file system ("tmpfs"), and only /usr/ is
               mounted from the file system configured as root device, in
               read-only mode. This enables fully state-less boots were the
               vendor-supplied OS is used as shipped, with only default
               configuration and no stored state in effect, as /etc/ and
               /var/ (as well as all other resources shipped in the root file
               system) are reset at boot and lost on shutdown. If this
               setting is set to "state" the root file system is mounted
               read-only, however /var/ is mounted as a volatile memory file
               system ("tmpfs"), so that the system boots up with the normal
               configuration applied, but all state reset at boot and lost at
               shutdown. If this setting is set to "overlay" the root file
               system is set up as "overlayfs" mount combining the read-only
               root directory with a writable "tmpfs", so that no
               modifications are made to disk, but the file system may be
               modified nonetheless with all changes being lost at reboot.
               For details, see systemd-volatile-root.service(8) and
               systemd-fstab-generator(8).
    
               Added in version 233.
    
           _quiet_
               Parameter understood by both the kernel and the system and
               service manager to control console log verbosity. For details,
               see systemd(1).
    
               Added in version 186.
    
           _debug_
               Parameter understood by both the kernel and the system and
               service manager to control console log verbosity. For details,
               see systemd(1).
    
               Added in version 205.
    
           _-b_ , _rd.emergency_ , _emergency_ , _rd.rescue_ , _rescue_ , _single_ , _s_ , _S_ , _1_ ,
           _2_ , _3_ , _4_ , _5_
               Parameters understood by the system and service manager, as
               compatibility and convenience options. For details, see
               systemd(1).
    
               Added in version 186.
    
           _locale.LANG=_ , _locale.LANGUAGE=_ , _locale.LC_CTYPE=_ ,
           _locale.LC_NUMERIC=_ , _locale.LC_TIME=_ , _locale.LC_COLLATE=_ ,
           _locale.LC_MONETARY=_ , _locale.LC_MESSAGES=_ , _locale.LC_PAPER=_ ,
           _locale.LC_NAME=_ , _locale.LC_ADDRESS=_ , _locale.LC_TELEPHONE=_ ,
           _locale.LC_MEASUREMENT=_ , _locale.LC_IDENTIFICATION=_
               Parameters understood by the system and service manager to
               control locale and language settings. For details, see
               systemd(1).
    
               Added in version 186.
    
           _fsck.mode=_ , _fsck.repair=_
               Parameters understood by the file system checker services. For
               details, see systemd-fsck@.service(8).
    
               Added in version 186.
    
           _quotacheck.mode=_
               Parameter understood by the file quota checker service. For
               details, see systemd-quotacheck@.service(8).
    
               Added in version 186.
    
           _systemd.journald.forward_to_syslog=_ ,
           _systemd.journald.forward_to_kmsg=_ ,
           _systemd.journald.forward_to_console=_ ,
           _systemd.journald.forward_to_wall=_
               Parameters understood by the journal service. For details, see
               systemd-journald.service(8).
    
               Added in version 186.
    
           _vconsole.keymap=_ , _vconsole.keymap_toggle=_ , _vconsole.font=_ ,
           _vconsole.font_map=_ , _vconsole.font_unimap=_
               Parameters understood by the virtual console setup logic. For
               details, see vconsole.conf(5).
    
               Added in version 186.
    
           _udev.log_level=_ , _rd.udev.log_level=_ , _udev.trace=_ , _rd.udev.trace=_ ,
           _udev.children_max=_ , _rd.udev.children_max=_ , _udev.exec_delay=_ ,
           _rd.udev.exec_delay=_ , _udev.event_timeout=_ , _rd.udev.event_timeout=_ ,
           _udev.timeout_signal=_ , _rd.udev.timeout_signal=_ ,
           _udev.blockdev_read_only_ , _rd.udev.blockdev_read_only_ , _net.ifnames=_ ,
           _net.naming_scheme=_
               Parameters understood by the device event managing daemon. For
               details, see systemd-udevd.service(8).
    
               Added in version 186.
    
           _plymouth.enable=_
               May be used to disable the Plymouth boot splash. For details,
               see **plymouth**(8).
    
               Added in version 186.
    
           _luks=_ , _rd.luks=_ , _luks.crypttab=_ , _rd.luks.crypttab=_ , _luks.name=_ ,
           _rd.luks.name=_ , _luks.uuid=_ , _rd.luks.uuid=_ , _luks.options=_ ,
           _rd.luks.options=_ , _luks.key=_ , _rd.luks.key=_
               Configures the LUKS full-disk encryption logic at boot. For
               details, see systemd-cryptsetup-generator(8).
    
               Added in version 186.
    
           _fstab=_ , _rd.fstab=_
               Configures the /etc/fstab logic at boot. For details, see
               systemd-fstab-generator(8).
    
               Added in version 186.
    
           _root=_ , _rootfstype=_ , _rootflags=_ , _ro_ , _rw_
               Configures the root file system and its file system type and
               mount options, as well as whether it shall be mounted
               read-only or read-write initially. For details, see
               systemd-fstab-generator(8).
    
               If _root=_ is not set (or set to "gpt-auto") the automatic root
               partition discovery implemented by
               systemd-gpt-auto-generator(8) will be in effect. In this case,
               _rootfstype=_ , _rootflags=_ , _ro_ , _rw_ will be interpreted by
               **systemd-gpt-auto-generator**.
    
               Added in version 215.
    
           _mount.usr=_ , _mount.usrfstype=_ , _mount.usrflags=_
               Configures the /usr file system (if required) and its file
               system type and mount options. For details, see
               systemd-fstab-generator(8).
    
               Added in version 235.
    
           _veritytab=_ , _rd.veritytab=_ , _roothash=_ , _systemd.verity=_ ,
           _rd.systemd.verity=_ , _systemd.verity_root_data=_ ,
           _systemd.verity_root_hash=_ , _systemd.verity_root_options=_ , _usrhash=_ ,
           _systemd.verity_usr_data=_ , _systemd.verity_usr_hash=_ ,
           _systemd.verity_usr_options=_
               Configures the integrity protection root hash for the root and
               /usr file systems, and other related parameters. For details,
               see systemd-veritysetup-generator(8).
    
               Added in version 233.
    
           _systemd.getty_auto=_
               Configures whether the serial-getty@.service will run. For
               details, see systemd-getty-generator(8).
    
               Added in version 250.
    
           _systemd.gpt_auto=_ , _rd.systemd.gpt_auto=_
               Configures whether GPT-based partition auto-discovery shall be
               attempted. For details, see systemd-gpt-auto-generator(8).
    
               Added in version 215.
    
           _systemd.image_policy=_
               When GPT-based partition auto-discovery is used, configures
               the image dissection policy string to apply, as per
               systemd.image-policy(7). For details see
               systemd-gpt-auto-generator(8).
    
               Added in version 254.
    
           _systemd.image_filter=_
               When GPT-based partition auto-discovery is used, configures
               the image dissection filter string to apply, as per
               systemd.image-filter(7). For details see
               systemd-gpt-auto-generator(8).
    
               Added in version 258.
    
           _systemd.default_timeout_start_sec=_
               Overrides the default start job timeout
               _DefaultTimeoutStartSec=_ at boot. For details, see
               systemd-system.conf(5).
    
               Added in version 230.
    
           _systemd.default_device_timeout_sec=_
               Overrides the default device timeout _DefaultDeviceTimeoutSec=_
               at boot. For details, see systemd-system.conf(5).
    
               Added in version 254.
    
           _systemd.watchdog_device=_
               Overrides the watchdog device path _WatchdogDevice=_. For
               details, see systemd-system.conf(5).
    
               Added in version 236.
    
           _systemd.watchdog_sec=_
               Overrides the watchdog timeout settings otherwise configured
               with _RuntimeWatchdog=_ , _RebootWatchdog=_ and _KExecWatchdogSec=_.
               Takes a time value (if no unit is specified, seconds is the
               implicitly assumed time unit) or the special strings "off" or
               "default". For details, see systemd-system.conf(5).
    
               Added in version 250.
    
           _systemd.watchdog_pre_sec=_
               Overrides the watchdog pre-timeout settings otherwise
               configured with _RuntimeWatchdogPreSec=_. Takes a time value (if
               no unit is specified, seconds is the implicitly assumed time
               unit) or the special strings "off" or "default". For details,
               see systemd-system.conf(5).
    
               Added in version 251.
    
           _systemd.watchdog_pretimeout_governor=_
               Overrides the watchdog pre-timeout settings otherwise
               configured with _RuntimeWatchdogPreGovernor=_. Takes a string
               value. For details, see systemd-system.conf(5).
    
               Added in version 251.
    
           _systemd.cpu_affinity=_
               Overrides the CPU affinity mask for the service manager and
               the default for all child processes it forks. This takes
               precedence over _CPUAffinity=_ , see systemd-system.conf(5) for
               details.
    
               Added in version 245.
    
           _modules_load=_ , _rd.modules_load=_
               Load a specific kernel module early at boot. For details, see
               systemd-modules-load.service(8).
    
               Added in version 187.
    
           _nameserver=_ , _domain=_
               Configures DNS server information and search domains, see
               systemd-resolved.service(8) for details.
    
               Added in version 253.
    
           _resume=_ , _resumeflags=_
               Enable resume from hibernation using the specified device and
               timeout options. All fstab(5)-style device identifiers are
               supported. For details, see
               systemd-hibernate-resume-generator(8).
    
               Added in version 217.
    
           _resume_offset=_
               Configure the page offset of the swap space from the resume
               device. For details, see
               systemd-hibernate-resume-generator(8).
    
               Added in version 254.
    
           _systemd.firstboot=_
               Takes a boolean argument, defaults to on. If off,
               **systemd-firstboot.service**(8) and
               systemd-homed-firstboot.service(1) will not query the user for
               basic system settings, even if the system boots up for the
               first time and the relevant settings are not initialized yet.
               Not to be confused with _systemd.condition_first_boot=_ (see
               below), which overrides the result of the _ConditionFirstBoot=_
               unit file condition, and thus controls more than just
               systemd-firstboot.service behaviour.
    
               Added in version 233.
    
           _systemd.condition_needs_update=_
               Takes a boolean argument. If specified, overrides the result
               of _ConditionNeedsUpdate=_ unit condition checks. See
               systemd.unit(5) for details.
    
               Added in version 246.
    
           _systemd.condition_first_boot=_
               Takes a boolean argument. If specified, overrides the result
               of _ConditionFirstBoot=_ unit condition checks. See
               systemd.unit(5) for details. Not to be confused with
               _systemd.firstboot=_ which only controls behaviour of the
               systemd-firstboot.service system service but has no effect on
               the condition check (see above).
    
               Added in version 246.
    
           _systemd.clock_usec=_
               Takes a decimal, numeric timestamp in μs since January 1st
               1970, 00:00am, to set the system clock to. The system time is
               set to the specified timestamp early during boot. It is not
               propagated to the hardware clock (RTC).
    
               Added in version 246.
    
           _systemd.random_seed=_
               Takes a base64 encoded random seed value to credit with full
               entropy to the kernel's random pool during early service
               manager initialization. This option is useful in testing
               environments where delays due to random pool initialization in
               entropy starved virtual machines shall be avoided.
    
               Note that if this option is used the seed is accessible to
               unprivileged programs from /proc/cmdline. This option is hence
               a security risk when used outside of test systems, since the
               (possibly) only seed used for initialization of the kernel's
               entropy pool might be easily acquired by unprivileged
               programs.
    
               It is recommended to pass 512 bytes of randomized data (as
               that matches the Linux kernel pool size), which may be
               generated with a command like the following:
    
                   dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0
    
               Again: do not use this option outside of testing environments,
               it is a security risk elsewhere, as secret key material
               derived from the entropy pool can possibly be reconstructed by
               unprivileged programs.
    
               Added in version 246.
    
           _systemd.allow_userspace_verity=_
               Takes a boolean argument. Controls whether disk images that
               are Verity protected may be authenticated in userspace
               signature checks via /etc/verity.d/ (and related directories)
               public key drop-ins, or whether in-kernel signature checking
               only. Defaults to on.
    
               Added in version 256.
    
           _systemd.hostname=_
               Accepts a hostname to set during early boot. If specified
               takes precedence over what is set in /etc/hostname. Note that
               this does not bar later runtime changes to the hostname, it
               simply controls the initial hostname set during early boot.
    
               Added in version 246.
    
           _systemd.tty.term.tty=_ , _systemd.tty.rows.tty=_ ,
           _systemd.tty.columns.tty=_
               These arguments allow configuring default values for _$TERM_ ,
               _TTYRows=_ , and _TTYColumns=_ for tty _tty_. Additionally,
               _systemd.tty.term.console_ will configure the _$TERM_ value used
               by **systemd** if not set explicitly using _TERM_ on the kernel
               command line. The tty name should be specified without the
               /dev/ prefix (e.g.  "systemd.tty.rows.ttyS0=80").
    
               Added in version 254.
    
           _systemd.battery_check=_
               Accepts a boolean argument. If false the boot-time battery
               charge check implemented by systemd-battery-check.service(8)
               is disabled.
    
               Added in version 254.
    
           _ifname=_ , _net.ifname_policy=_
               Controls interface naming policies, implemented by
               systemd-network-generator.service(8).
    
               Added in version 245.
    
           _systemd.tpm2_allow_clear=_
               Controls whether to allow clearing of the TPM chip,
               implemented by **systemd-tpm2-clear**(8).
    
               Added in version 258.
    
           _systemd.tpm2_wait=_
               Controls whether to wait for a TPM2 device at boot,
               implemented by systemd-tpm2-generator(8).
    
               Added in version 256.
    
           _systemd.factory_reset=_
               Controls whether to to boot into factory reset mode,
               implemented by systemd-factory-reset-generator(8),
               systemd-repart(8), and other tools.
    
               Added in version 258.
    


## NOTES



            1. kernel-parameters.html
               https://docs.kernel.org/admin-guide/kernel-parameters.html
    


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