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
dracut.cmdline(7), or 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_reboot, 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.default_standard_output=, systemd.default_standard_error=,
systemd.setenv=, systemd.machine_id=, systemd.set_credential=,
systemd.import_credentials=
Parameters understood by the system and service manager to control
system behavior. For details, see systemd(1).
systemd.mask=, systemd.wants=, systemd.debug_shell
Additional parameters understood by systemd-debug-generator(8), to
mask or start specific units at boot, or invoke a debug shell on
tty9.
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.
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.
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).
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).
quiet
Parameter understood by both the kernel and the system and service
manager to control console log verbosity. For details, see
systemd(1).
debug
Parameter understood by both the kernel and the system and service
manager to control console log verbosity. For details, see
systemd(1).
-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).
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).
fsck.mode=, fsck.repair=
Parameters understood by the file system checker services. For
details, see systemd-fsck@.service(8).
quotacheck.mode=
Parameter understood by the file quota checker service. For
details, see systemd-quotacheck.service(8).
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).
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).
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).
plymouth.enable=
May be used to disable the Plymouth boot splash. For details, see
plymouth(8).
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).
fstab=, rd.fstab=
Configures the /etc/fstab logic at boot. For details, see systemd-
fstab-generator(8).
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).
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).
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).
systemd.getty_auto=
Configures whether the serial-getty@.service will run. For details,
see systemd-getty-generator(8).
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).
systemd.default_timeout_start_sec=
Overrides the default start job timeout DefaultTimeoutStartSec= at
boot. For details, see systemd-system.conf(5).
systemd.watchdog_device=
Overrides the watchdog device path WatchdogDevice=. For details,
see systemd-system.conf(5).
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).
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).
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).
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.
modules_load=, rd.modules_load=
Load a specific kernel module early at boot. For details, see
systemd-modules-load.service(8).
resume=, resumeflags=
Enables resume from hibernation using the specified device and
mount options. All fstab(5)-like paths are supported. For details,
see systemd-hibernate-resume-generator(8).
systemd.firstboot=
Takes a boolean argument, defaults to on. If off, systemd-
firstboot.service(8) 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.
systemd.condition-needs-update=
Takes a boolean argument. If specified, overrides the result of
ConditionNeedsUpdate= unit condition checks. See systemd.unit(5)
for details.
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).
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).
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.
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.
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.
SEE ALSO
systemd(1), systemd-system.conf(5), bootparam(7), dracut.cmdline(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 252 KERNEL-COMMAND-LINE(7)
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