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. 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
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).
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.
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.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.
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).
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.
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.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).
systemd.default_timeout_start_sec=¶Overrides the default start job timeout DefaultTimeoutStartSec= at
boot. For details, see
systemd-system.conf(5).
systemd.default_device_timeout_sec=¶Overrides the default device timeout DefaultDeviceTimeoutSec= 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).
nameserver=, domain=¶Configures DNS server information and search domains, see systemd-resolved.service(8) for details.
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).
resume_offset=¶Configure the page offset of the swap space from the resume device. For details, see systemd-hibernate-resume-generator(8).
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.
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.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.
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.
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").
systemd.battery_check=¶Accepts a boolean argument. If false the boot-time battery charge check implemented by systemd-battery-check.service(8) is disabled.
ifname=, net.ifname_policy=¶Controls interface naming policies, implemented by systemd-network-generator.service(8).
systemd.tpm2_wait=¶Controls whether to wait for a TPM2 device at boot, implemented by systemd-tpm2-generator(8).
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), 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)