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KERNEL-COMMAND-LINE(7) kernel-command-line KERNEL-COMMAND-LINE(7)

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. In addition, various systemd tools look at the EFI variable "SystemdOptions" (if available). Both sources are combined, but the kernel command line has higher priority. Please note that the EFI variable is only used by systemd tools, and is ignored by the kernel and other user space tools, so it is not a replacement for the kernel command line.

For command line parameters understood by the kernel, please see kernel-parameters.html[1] and bootparam(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.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 value "state". 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.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.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's 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_wait=

Controls whether to wait for a TPM2 device at boot, implemented by systemd-tpm2-generator(8).

Added in version 256.

HISTORY

systemd 252

Kernel command-line arguments systemd.unified_cgroup_hierarchy and systemd.legacy_systemd_cgroup_controller were deprecated. Please switch to the unified cgroup hierarchy.

Added in version 252.

SEE ALSO

systemd(1), systemd-system.conf(5), bootparam(7), systemd.system-credentials(7), smbios-type-11(7), systemd-debug-generator(8), systemd-fsck@.service(8), systemd-quotacheck.service(8), systemd-journald.service(8), systemd-vconsole-setup.service(8), systemd-udevd.service(8), plymouth(8), systemd-cryptsetup-generator(8), systemd-veritysetup-generator(8), systemd-fstab-generator(8), systemd-getty-generator(8), systemd-gpt-auto-generator(8), systemd-volatile-root.service(8), systemd-modules-load.service(8), systemd-backlight@.service(8), systemd-rfkill.service(8), systemd-hibernate-resume-generator(8), systemd-firstboot.service(8), bootctl(1)

NOTES

1.
kernel-parameters.html
https://docs.kernel.org/admin-guide/kernel-parameters.html
systemd 257