kernel-command-line - Kernel command line parameters


          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 m[blue]kernel-parameters.htmlm[][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.

          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_error=, systemd.setenv=,
          systemd.machine_id=, systemd.unified_cgroup_hierarchy,
              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_success_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.

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              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.

              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).

              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).

              Parameter understood by both the kernel and the system
              and service manager to control console log verbosity.
              For details, see systemd(1).

              Parameter understood by both the kernel and the system
              and service manager to control console log verbosity.
              For details, see systemd(1).

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          -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).

              Parameters understood by the file system checker
              services. For details, see systemd-fsck@.service(8).

              Parameter understood by the file quota checker service.
              For details, see systemd-quotacheck.service(8).

              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).

              May be used to disable the Plymouth boot splash. For
              details, see plymouth(8).

          luks=, rd.luks=, luks.crypttab=, rd.luks.crypttab=,
,, luks.uuid=, rd.luks.uuid=,
          luks.options=, rd.luks.options=, luks.key=, rd.luks.key=
              Configures the LUKS full-disk encryption logic at boot.

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              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

          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-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-

              Overwrites the default start job timeout
              DefaultTimeoutStartSec= at boot. For details, see

              Overwrites the watchdog device path WatchdogDevice=. For
              details, see systemd-system.conf(5).

              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-

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              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.

              Takes a boolean argument. If specified, overrides the
              result of ConditionNeedsUpdate= unit condition checks.
              See systemd.unit(5) for details.

              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).

              Takes a decimal, numeric timestamp in mcs 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

              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

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              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.

              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(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)

           1. kernel-parameters.html

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