Provided by: systemd_249.11-0ubuntu3_amd64 bug


       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 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


       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,
           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=, 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.

           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).

       -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=,
           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-

           Parameter understood by the file quota checker service. For details, see systemd-

       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-

       vconsole.keymap=, vconsole.keymap_toggle=, vconsole.font=, vconsole.font_map=,
           Parameters understood by the virtual console setup logic. For details, see

       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-

           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. For details, see systemd-

       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

       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).

           Overwrites the default start job timeout DefaultTimeoutStartSec= at boot. For details,
           see systemd-system.conf(5).

           Overwrites the watchdog device path WatchdogDevice=. For details, see systemd-

           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-

       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-

           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 ┬Ás 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).

           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.

           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