kernel-command-line

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 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[1] and bootparam(7).

       For command line parameters understood by the initial RAM disk, please
       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.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 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=
           Configures the integrity protection root hash for the root file
           system, and other related parameters. For details, see systemd-
           veritysetup-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=
           Overwrites the default start job timeout DefaultTimeoutStartSec= at
           boot. For details, see systemd-system.conf(5).

       systemd.watchdog_device=
           Overwrites the watchdog device path WatchdogDevice=. 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 <micro>s 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
       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-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://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

systemd 249                                             KERNEL-COMMAND-LINE(7)