NAME
kernel-command-line - Kernel command line parametersSYNOPSIS
/proc/cmdlineDESCRIPTION
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 [email protected]
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:
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=
dd if=/dev/urandom bs=512 count=1 status=none | base64 -w 0
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 252Kernel 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
systemd 252 |