kernel-command-line
systemd
kernel-command-line
7
kernel-command-line
Kernel command line parameters
/proc/cmdline
Description
The kernel, the initial RAM disk (initrd) and basic userspace functionality 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
and
bootparam7.
For command line parameters understood by the initial RAM
disk, please see
dracut.cmdline7,
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.early_core_pattern=
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.unified_cgroup_hierarchy
systemd.legacy_systemd_cgroup_controller
Parameters understood by the system and service
manager to control system behavior. For details, see
systemd1.
systemd.mask=
systemd.wants=
systemd.debug_shell
Additional parameters understood by
systemd-debug-generator8,
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-generator8, 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
core5 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@.service8
and
systemd-rfkill.service8.
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.service8
and
systemd-fstab-generator8.
quiet
Parameter understood by both the kernel and the system
and service manager to control console log verbosity. For
details, see
systemd1.
debug
Parameter understood by both the kernel and the system
and service manager to control console log verbosity. For
details, see
systemd1.
-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
systemd1.
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
systemd1.
fsck.mode=
fsck.repair=
Parameters understood by the file system checker
services. For details, see
systemd-fsck@.service8.
quotacheck.mode=
Parameter understood by the file quota checker
service. For details, see
systemd-quotacheck.service8.
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.service8.
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.conf5.
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.service8.
plymouth.enable=
May be used to disable the Plymouth boot splash. For
details, see
plymouth8.
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-generator8.
fstab=
rd.fstab=
Configures the /etc/fstab logic
at boot. For details, see
systemd-fstab-generator8.
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-generator8.
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-generator8.
roothash=
systemd.verity=
rd.systemd.verity=
systemd.verity_root_data=
systemd.verity_root_hash=
Configures the integrity protection root hash for the root file system, and other related
parameters. For details, see
systemd-veritysetup-generator8.
systemd.gpt_auto=
rd.systemd.gpt_auto=
Configures whether GPT based partition auto-discovery
shall be attempted. For details, see
systemd-gpt-auto-generator8.
systemd.default_timeout_start_sec=
Overwrites the default start job timeout DefaultTimeoutStartSec= at boot. For details,
see systemd-system.conf5.
systemd.watchdog_device=
Overwrites the watchdog device path WatchdogDevice=. For details, see
systemd-system.conf5.
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.conf5
for details.
modules_load=
rd.modules_load=
Load a specific kernel module early at boot. For
details, see
systemd-modules-load.service8.
resume=
resumeflags=
Enables resume from hibernation using the specified
device and mount options. All
fstab5-like
paths are supported. For details, see
systemd-hibernate-resume-generator8.
systemd.firstboot=
Takes a boolean argument, defaults to on. If off,
systemd-firstboot.service8
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.unit5 for
details.
systemd.condition-first-boot=
Takes a boolean argument. If specified, overrides the result of
ConditionFirstBoot= unit condition checks. See
systemd.unit5 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.
See Also
systemd1,
systemd-system.conf5,
bootparam7,
dracut.cmdline7,
systemd-debug-generator8,
systemd-fsck@.service8,
systemd-quotacheck.service8,
systemd-journald.service8,
systemd-vconsole-setup.service8,
systemd-udevd.service8,
plymouth8,
systemd-cryptsetup-generator8,
systemd-veritysetup-generator8,
systemd-fstab-generator8,
systemd-gpt-auto-generator8,
systemd-volatile-root.service8,
systemd-modules-load.service8,
systemd-backlight@.service8,
systemd-rfkill.service8,
systemd-hibernate-resume-generator8,
systemd-firstboot.service8,
bootctl1