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NAME | SYNOPSIS | DESCRIPTION | CORE OS COMMAND LINE ARGUMENTS | HISTORY | SEE ALSO | NOTES | COLOPHON |
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KERNEL-COMMAND-LINE(7) kernel-command-line KERNEL-COMMAND-LINE(7)
kernel-command-line - Kernel command line parameters
/proc/cmdline
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] and bootparam(7).
For command line parameters understood by the initrd, see the
documentation of the specific initrd implementation of your
installation.
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
[email protected](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 [email protected](8).
Added in version 186.
quotacheck.mode=
Parameter understood by the file quota checker service. For
details, see [email protected](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 [email protected] 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.
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.
systemd(1), systemd-system.conf(5), bootparam(7),
systemd.system-credentials(7), smbios-type-11(7),
systemd-debug-generator(8), [email protected](8),
[email protected](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),
[email protected](8), systemd-rfkill.service(8),
systemd-hibernate-resume-generator(8),
systemd-firstboot.service(8), bootctl(1)
1. kernel-parameters.html
https://docs.kernel.org/admin-guide/kernel-parameters.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 KERNEL-COMMAND-LINE(7)
Pages that refer to this page: systemd(1), systemd-nspawn(1), hostname(5), machine-id(5), systemd.exec(5), smbios-type-11(7), systemd.directives(7), systemd.index(7), systemd.system-credentials(7), systemd-debug-generator(8), systemd-fstab-generator(8), systemd-getty-generator(8), systemd-hibernate-resume-generator(8), systemd-import-generator(8), systemd-rfkill.service(8), systemd-run-generator(8), systemd-ssh-generator(8), systemd-tpm2-generator(8), systemd-volatile-root.service(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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