path: root/upstream/debian-unstable/man7/kernel-command-line.7

'\" t
.TH "KERNEL\-COMMAND\-LINE" "7" "" "systemd 256~rc3" "kernel-command-line"
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.SH "NAME"
kernel-command-line \- Kernel command line parameters
.SH "SYNOPSIS"
.PP
/proc/cmdline
.SH "DESCRIPTION"
.PP
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
\fIthe EFI variable is only used by systemd tools, and is ignored by the kernel and other user space tools\fR, so it is not a replacement for the kernel command line\&.
.PP
For command line parameters understood by the kernel, please see
\m[blue]\fBkernel\-parameters\&.html\fR\m[]\&\s-2\u[1]\d\s+2
and
\fBbootparam\fR(7)\&.
.PP
For command line parameters understood by the initrd, see the documentation of the specific initrd implementation of your installation\&.
.SH "CORE OS COMMAND LINE ARGUMENTS"
.PP
\fIsystemd\&.unit=\fR, \fIrd\&.systemd\&.unit=\fR, \fIsystemd\&.dump_core\fR, \fIsystemd\&.crash_chvt\fR, \fIsystemd\&.crash_shell\fR, \fIsystemd\&.crash_action=\fR, \fIsystemd\&.confirm_spawn\fR, \fIsystemd\&.service_watchdogs\fR, \fIsystemd\&.show_status\fR, \fIsystemd\&.status_unit_format=\fR, \fIsystemd\&.log_target=\fR, \fIsystemd\&.log_level=\fR, \fIsystemd\&.log_location=\fR, \fIsystemd\&.log_color\fR, \fIsystemd\&.log_ratelimit_kmsg\fR, \fIsystemd\&.default_standard_output=\fR, \fIsystemd\&.default_standard_error=\fR, \fIsystemd\&.setenv=\fR, \fIsystemd\&.machine_id=\fR, \fIsystemd\&.set_credential=\fR, \fIsystemd\&.set_credential_binary=\fR, \fIsystemd\&.import_credentials=\fR, \fIsystemd\&.reload_limit_interval_sec=\fR, \fIsystemd\&.reload_limit_burst=\fR
.RS 4
Parameters understood by the system and service manager to control system behavior\&. For details, see
\fBsystemd\fR(1)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIsystemd\&.mask=\fR, \fIsystemd\&.wants=\fR, \fIsystemd\&.debug_shell\fR, \fIsystemd\&.default_debug_tty=\fR
.RS 4
Additional parameters understood by
\fBsystemd-debug-generator\fR(8), to mask or start specific units at boot, or invoke a debug shell on tty9\&.
.sp
Added in version 215\&.
.RE
.PP
\fIsystemd\&.run=\fR, \fIsystemd\&.run_success_action=\fR, \fIsystemd\&.run_failure_action=\fR
.RS 4
Additional parameters understood by
\fBsystemd-run-generator\fR(8), to run a command line specified on the kernel command line as system service after booting up\&.
.sp
Added in version 240\&.
.RE
.PP
\fIsystemd\&.early_core_pattern=\fR
.RS 4
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
\fBcore\fR(5)
for details\&.
.sp
Added in version 240\&.
.RE
.PP
\fIsystemd\&.restore_state=\fR
.RS 4
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
\fBsystemd-backlight@.service\fR(8)
and
\fBsystemd-rfkill.service\fR(8)\&.
.sp
Added in version 209\&.
.RE
.PP
\fIsystemd\&.ssh_auto=\fR, \fIsystemd\&.ssh_listen=\fR
.RS 4
These parameters are interpreted by
\fBsystemd-ssh-generator\fR(8)
and may be used to control SSH sockets the system shall be reachable on\&.
.sp
Added in version 256\&.
.RE
.PP
\fIsystemd\&.volatile=\fR
.RS 4
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
\fBsystemd-volatile-root.service\fR(8)
and
\fBsystemd-fstab-generator\fR(8)\&.
.sp
Added in version 233\&.
.RE
.PP
\fIquiet\fR
.RS 4
Parameter understood by both the kernel and the system and service manager to control console log verbosity\&. For details, see
\fBsystemd\fR(1)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIdebug\fR
.RS 4
Parameter understood by both the kernel and the system and service manager to control console log verbosity\&. For details, see
\fBsystemd\fR(1)\&.
.sp
Added in version 205\&.
.RE
.PP
\fI\-b\fR, \fIrd\&.emergency\fR, \fIemergency\fR, \fIrd\&.rescue\fR, \fIrescue\fR, \fIsingle\fR, \fIs\fR, \fIS\fR, \fI1\fR, \fI2\fR, \fI3\fR, \fI4\fR, \fI5\fR
.RS 4
Parameters understood by the system and service manager, as compatibility and convenience options\&. For details, see
\fBsystemd\fR(1)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIlocale\&.LANG=\fR, \fIlocale\&.LANGUAGE=\fR, \fIlocale\&.LC_CTYPE=\fR, \fIlocale\&.LC_NUMERIC=\fR, \fIlocale\&.LC_TIME=\fR, \fIlocale\&.LC_COLLATE=\fR, \fIlocale\&.LC_MONETARY=\fR, \fIlocale\&.LC_MESSAGES=\fR, \fIlocale\&.LC_PAPER=\fR, \fIlocale\&.LC_NAME=\fR, \fIlocale\&.LC_ADDRESS=\fR, \fIlocale\&.LC_TELEPHONE=\fR, \fIlocale\&.LC_MEASUREMENT=\fR, \fIlocale\&.LC_IDENTIFICATION=\fR
.RS 4
Parameters understood by the system and service manager to control locale and language settings\&. For details, see
\fBsystemd\fR(1)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIfsck\&.mode=\fR, \fIfsck\&.repair=\fR
.RS 4
Parameters understood by the file system checker services\&. For details, see
\fBsystemd-fsck@.service\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIquotacheck\&.mode=\fR
.RS 4
Parameter understood by the file quota checker service\&. For details, see
\fBsystemd-quotacheck.service\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIsystemd\&.journald\&.forward_to_syslog=\fR, \fIsystemd\&.journald\&.forward_to_kmsg=\fR, \fIsystemd\&.journald\&.forward_to_console=\fR, \fIsystemd\&.journald\&.forward_to_wall=\fR
.RS 4
Parameters understood by the journal service\&. For details, see
\fBsystemd-journald.service\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIvconsole\&.keymap=\fR, \fIvconsole\&.keymap_toggle=\fR, \fIvconsole\&.font=\fR, \fIvconsole\&.font_map=\fR, \fIvconsole\&.font_unimap=\fR
.RS 4
Parameters understood by the virtual console setup logic\&. For details, see
\fBvconsole.conf\fR(5)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIudev\&.log_level=\fR, \fIrd\&.udev\&.log_level=\fR, \fIudev\&.children_max=\fR, \fIrd\&.udev\&.children_max=\fR, \fIudev\&.exec_delay=\fR, \fIrd\&.udev\&.exec_delay=\fR, \fIudev\&.event_timeout=\fR, \fIrd\&.udev\&.event_timeout=\fR, \fIudev\&.timeout_signal=\fR, \fIrd\&.udev\&.timeout_signal=\fR, \fIudev\&.blockdev_read_only\fR, \fIrd\&.udev\&.blockdev_read_only\fR, \fInet\&.ifnames=\fR, \fInet\&.naming_scheme=\fR
.RS 4
Parameters understood by the device event managing daemon\&. For details, see
\fBsystemd-udevd.service\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIplymouth\&.enable=\fR
.RS 4
May be used to disable the Plymouth boot splash\&. For details, see
\fBplymouth\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIluks=\fR, \fIrd\&.luks=\fR, \fIluks\&.crypttab=\fR, \fIrd\&.luks\&.crypttab=\fR, \fIluks\&.name=\fR, \fIrd\&.luks\&.name=\fR, \fIluks\&.uuid=\fR, \fIrd\&.luks\&.uuid=\fR, \fIluks\&.options=\fR, \fIrd\&.luks\&.options=\fR, \fIluks\&.key=\fR, \fIrd\&.luks\&.key=\fR
.RS 4
Configures the LUKS full\-disk encryption logic at boot\&. For details, see
\fBsystemd-cryptsetup-generator\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIfstab=\fR, \fIrd\&.fstab=\fR
.RS 4
Configures the
/etc/fstab
logic at boot\&. For details, see
\fBsystemd-fstab-generator\fR(8)\&.
.sp
Added in version 186\&.
.RE
.PP
\fIroot=\fR, \fIrootfstype=\fR, \fIrootflags=\fR, \fIro\fR, \fIrw\fR
.RS 4
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
\fBsystemd-fstab-generator\fR(8)\&.
.sp
If
\fIroot=\fR
is not set (or set to
"gpt\-auto") the automatic root partition discovery implemented by
\fBsystemd-gpt-auto-generator\fR(8)
will be in effect\&. In this case
\fIrootfstype=\fR,
\fIrootflags=\fR,
\fIro\fR,
\fIrw\fR
will be interpreted by
\fBsystemd\-gpt\-auto\-generator\fR\&.
.sp
Added in version 215\&.
.RE
.PP
\fImount\&.usr=\fR, \fImount\&.usrfstype=\fR, \fImount\&.usrflags=\fR
.RS 4
Configures the /usr file system (if required) and its file system type and mount options\&. For details, see
\fBsystemd-fstab-generator\fR(8)\&.
.sp
Added in version 235\&.
.RE
.PP
\fIveritytab=\fR, \fIrd\&.veritytab=\fR, \fIroothash=\fR, \fIsystemd\&.verity=\fR, \fIrd\&.systemd\&.verity=\fR, \fIsystemd\&.verity_root_data=\fR, \fIsystemd\&.verity_root_hash=\fR, \fIsystemd\&.verity\&.root_options=\fR, \fIusrhash=\fR, \fIsystemd\&.verity_usr_data=\fR, \fIsystemd\&.verity_usr_hash=\fR, \fIsystemd\&.verity_usr_options=\fR
.RS 4
Configures the integrity protection root hash for the root and
/usr
file systems, and other related parameters\&. For details, see
\fBsystemd-veritysetup-generator\fR(8)\&.
.sp
Added in version 233\&.
.RE
.PP
\fIsystemd\&.getty_auto=\fR
.RS 4
Configures whether the
serial\-getty@\&.service
will run\&. For details, see
\fBsystemd-getty-generator\fR(8)\&.
.sp
Added in version 250\&.
.RE
.PP
\fIsystemd\&.gpt_auto=\fR, \fIrd\&.systemd\&.gpt_auto=\fR
.RS 4
Configures whether GPT\-based partition auto\-discovery shall be attempted\&. For details, see
\fBsystemd-gpt-auto-generator\fR(8)\&.
.sp
Added in version 215\&.
.RE
.PP
\fIsystemd\&.image_policy=\fR, \fIrd\&.systemd\&.image_policy=\fR
.RS 4
When GPT\-based partition auto\-discovery is used, configures the image dissection policy string to apply, as per
\fBsystemd.image-policy\fR(7)\&. For details see
\fBsystemd-gpt-auto-generator\fR(8)\&.
.sp
Added in version 254\&.
.RE
.PP
\fIsystemd\&.default_timeout_start_sec=\fR
.RS 4
Overrides the default start job timeout
\fIDefaultTimeoutStartSec=\fR
at boot\&. For details, see
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 230\&.
.RE
.PP
\fIsystemd\&.default_device_timeout_sec=\fR
.RS 4
Overrides the default device timeout
\fIDefaultDeviceTimeoutSec=\fR
at boot\&. For details, see
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 254\&.
.RE
.PP
\fIsystemd\&.watchdog_device=\fR
.RS 4
Overrides the watchdog device path
\fIWatchdogDevice=\fR\&. For details, see
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 236\&.
.RE
.PP
\fIsystemd\&.watchdog_sec=\fR
.RS 4
Overrides the watchdog timeout settings otherwise configured with
\fIRuntimeWatchdog=\fR,
\fIRebootWatchdog=\fR
and
\fIKExecWatchdogSec=\fR\&. 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
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 250\&.
.RE
.PP
\fIsystemd\&.watchdog_pre_sec=\fR
.RS 4
Overrides the watchdog pre\-timeout settings otherwise configured with
\fIRuntimeWatchdogPreSec=\fR\&. 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
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 251\&.
.RE
.PP
\fIsystemd\&.watchdog_pretimeout_governor=\fR
.RS 4
Overrides the watchdog pre\-timeout settings otherwise configured with
\fIRuntimeWatchdogPreGovernor=\fR\&. Takes a string value\&. For details, see
\fBsystemd-system.conf\fR(5)\&.
.sp
Added in version 251\&.
.RE
.PP
\fIsystemd\&.cpu_affinity=\fR
.RS 4
Overrides the CPU affinity mask for the service manager and the default for all child processes it forks\&. This takes precedence over
\fICPUAffinity=\fR, see
\fBsystemd-system.conf\fR(5)
for details\&.
.sp
Added in version 245\&.
.RE
.PP
\fImodules_load=\fR, \fIrd\&.modules_load=\fR
.RS 4
Load a specific kernel module early at boot\&. For details, see
\fBsystemd-modules-load.service\fR(8)\&.
.sp
Added in version 187\&.
.RE
.PP
\fInameserver=\fR, \fIdomain=\fR
.RS 4
Configures DNS server information and search domains, see
\fBsystemd-resolved.service\fR(8)
for details\&.
.sp
Added in version 253\&.
.RE
.PP
\fIresume=\fR, \fIresumeflags=\fR
.RS 4
Enable resume from hibernation using the specified device and timeout options\&. All
\fBfstab\fR(5)\-style device identifiers are supported\&. For details, see
\fBsystemd-hibernate-resume-generator\fR(8)\&.
.sp
Added in version 217\&.
.RE
.PP
\fIresume_offset=\fR
.RS 4
Configure the page offset of the swap space from the resume device\&. For details, see
\fBsystemd-hibernate-resume-generator\fR(8)\&.
.sp
Added in version 254\&.
.RE
.PP
\fIsystemd\&.firstboot=\fR
.RS 4
Takes a boolean argument, defaults to on\&. If off,
\fBsystemd-firstboot.service\fR(8)
and
\fBsystemd-homed-firstboot.service\fR(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
\fIsystemd\&.condition_first_boot=\fR
(see below), which overrides the result of the
\fIConditionFirstBoot=\fR
unit file condition, and thus controls more than just
systemd\-firstboot\&.service
behaviour\&.
.sp
Added in version 233\&.
.RE
.PP
\fIsystemd\&.condition_needs_update=\fR
.RS 4
Takes a boolean argument\&. If specified, overrides the result of
\fIConditionNeedsUpdate=\fR
unit condition checks\&. See
\fBsystemd.unit\fR(5)
for details\&.
.sp
Added in version 246\&.
.RE
.PP
\fIsystemd\&.condition_first_boot=\fR
.RS 4
Takes a boolean argument\&. If specified, overrides the result of
\fIConditionFirstBoot=\fR
unit condition checks\&. See
\fBsystemd.unit\fR(5)
for details\&. Not to be confused with
\fIsystemd\&.firstboot=\fR
which only controls behaviour of the
systemd\-firstboot\&.service
system service but has no effect on the condition check (see above)\&.
.sp
Added in version 246\&.
.RE
.PP
\fIsystemd\&.clock_usec=\fR
.RS 4
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)\&.
.sp
Added in version 246\&.
.RE
.PP
\fIsystemd\&.random_seed=\fR
.RS 4
Takes a base64 encoded random seed value to credit with full entropy to the kernel\*(Aqs 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\&.
.sp
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\*(Aqs entropy pool might be easily acquired by unprivileged programs\&.
.sp
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:
.sp
.if n \{\
.RS 4
.\}
.nf
dd if=/dev/urandom bs=512 count=1 status=none | base64 \-w 0
.fi
.if n \{\
.RE
.\}
.sp
Again: do not use this option outside of testing environments, it\*(Aqs a security risk elsewhere, as secret key material derived from the entropy pool can possibly be reconstructed by unprivileged programs\&.
.sp
Added in version 246\&.
.RE
.PP
\fIsystemd\&.allow_userspace_verity=\fR
.RS 4
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\&.
.sp
Added in version 256\&.
.RE
.PP
\fIsystemd\&.hostname=\fR
.RS 4
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\&.
.sp
Added in version 246\&.
.RE
.PP
\fIsystemd\&.tty\&.term\&.\fR\fI\fItty\fR\fR\fI=\fR, \fIsystemd\&.tty\&.rows\&.\fR\fI\fItty\fR\fR\fI=\fR, \fIsystemd\&.tty\&.columns\&.\fR\fI\fItty\fR\fR\fI=\fR
.RS 4
These arguments allow configuring default values for
\fI$TERM\fR,
\fITTYRows=\fR, and
\fITTYColumns=\fR
for tty
\fItty\fR\&. Additionally,
\fIsystemd\&.tty\&.term\&.console\fR
will configure the
\fI$TERM\fR
value used by
\fBsystemd\fR
if not set explicitly using
\fITERM\fR
on the kernel command line\&. The tty name should be specified without the
/dev/
prefix (e\&.g\&.
"systemd\&.tty\&.rows\&.ttyS0=80")\&.
.sp
Added in version 254\&.
.RE
.PP
\fIsystemd\&.battery_check=\fR
.RS 4
Accepts a boolean argument\&. If false the boot\-time battery charge check implemented by
\fBsystemd-battery-check.service\fR(8)
is disabled\&.
.sp
Added in version 254\&.
.RE
.PP
\fIifname=\fR, \fInet\&.ifname_policy=\fR
.RS 4
Controls interface naming policies, implemented by
\fBsystemd-network-generator.service\fR(8)\&.
.sp
Added in version 245\&.
.RE
.PP
\fIsystemd\&.tpm2_wait=\fR
.RS 4
Controls whether to wait for a TPM2 device at boot, implemented by
\fBsystemd-tpm2-generator\fR(8)\&.
.sp
Added in version 256\&.
.RE
.SH "HISTORY"
.PP
systemd 252
.RS 4
Kernel command\-line arguments
\fIsystemd\&.unified_cgroup_hierarchy\fR
and
\fIsystemd\&.legacy_systemd_cgroup_controller\fR
were deprecated\&. Please switch to the unified cgroup hierarchy\&.
.sp
Added in version 252\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsystemd-system.conf\fR(5), \fBbootparam\fR(7), \fBsystemd.system-credentials\fR(7), \fBsmbios-type-11\fR(7), \fBsystemd-debug-generator\fR(8), \fBsystemd-fsck@.service\fR(8), \fBsystemd-quotacheck.service\fR(8), \fBsystemd-journald.service\fR(8), \fBsystemd-vconsole-setup.service\fR(8), \fBsystemd-udevd.service\fR(8), \fBplymouth\fR(8), \fBsystemd-cryptsetup-generator\fR(8), \fBsystemd-veritysetup-generator\fR(8), \fBsystemd-fstab-generator\fR(8), \fBsystemd-getty-generator\fR(8), \fBsystemd-gpt-auto-generator\fR(8), \fBsystemd-volatile-root.service\fR(8), \fBsystemd-modules-load.service\fR(8), \fBsystemd-backlight@.service\fR(8), \fBsystemd-rfkill.service\fR(8), \fBsystemd-hibernate-resume-generator\fR(8), \fBsystemd-firstboot.service\fR(8), \fBbootctl\fR(1)
.SH "NOTES"
.IP " 1." 4
kernel-parameters.html
.RS 4
\%https://docs.kernel.org/admin-guide/kernel-parameters.html
.RE