path: root/man/kernel-command-line.xml

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<refentry id="kernel-command-line">

  <refentryinfo>
    <title>kernel-command-line</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>Lennart</firstname>
        <surname>Poettering</surname>
        <email>lennart@poettering.net</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>kernel-command-line</refentrytitle>
    <manvolnum>7</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>kernel-command-line</refname>
    <refpurpose>Kernel command line parameters</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>/proc/cmdline</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The kernel, the initial RAM disk (initrd) and
    basic userspace functionality may be configured at boot via
    kernel command line arguments.</para>

    <para>For command line parameters understood by the kernel, please
    see
    <ulink url="https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html"><filename>kernel-parameters.html</filename></ulink>
    and
    <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>

    <para>For command line parameters understood by the initial RAM
    disk, please see
    <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
    or the documentation of the specific initrd implementation of your
    installation.</para>
  </refsect1>

  <refsect1>
    <title>Core OS Command Line Arguments</title>

    <variablelist class='kernel-commandline-options'>
      <varlistentry>
        <term><varname>systemd.unit=</varname></term>
        <term><varname>rd.systemd.unit=</varname></term>
        <term><varname>systemd.dump_core</varname></term>
        <term><varname>systemd.crash_chvt</varname></term>
        <term><varname>systemd.crash_shell</varname></term>
        <term><varname>systemd.crash_reboot</varname></term>
        <term><varname>systemd.confirm_spawn</varname></term>
        <term><varname>systemd.service_watchdogs</varname></term>
        <term><varname>systemd.show_status</varname></term>
        <term><varname>systemd.log_target=</varname></term>
        <term><varname>systemd.log_level=</varname></term>
        <term><varname>systemd.log_location=</varname></term>
        <term><varname>systemd.log_color</varname></term>
        <term><varname>systemd.default_standard_output=</varname></term>
        <term><varname>systemd.default_standard_error=</varname></term>
        <term><varname>systemd.setenv=</varname></term>
        <term><varname>systemd.machine_id=</varname></term>
        <term><varname>systemd.unified_cgroup_hierarchy</varname></term>
        <term><varname>systemd.legacy_systemd_cgroup_controller</varname></term>
        <listitem>
          <para>Parameters understood by the system and service
          manager to control system behavior. For details, see
          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.mask=</varname></term>
        <term><varname>systemd.wants=</varname></term>
        <term><varname>systemd.debug_shell</varname></term>
        <listitem>
          <para>Additional parameters understood by
          <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
          to mask or start specific units at boot, or invoke a debug
          shell on tty9.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.restore_state=</varname></term>
        <listitem>
          <para>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
          <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
          and
          <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.volatile=</varname></term>
        <listitem>
          <para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
          the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
          directory and <filename>/var</filename> are mounted as specified on the kernel command line or
          <filename>/etc/fstab</filename>, 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 (<literal>tmpfs</literal>), and only
          <filename>/usr</filename> 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 <filename>/etc</filename> and <filename>/var</filename> (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 <literal>state</literal> the root file system is mounted as usual, however
          <filename>/var</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
          system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. For details,
          see
          <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
          and
          <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>quiet</varname></term>
        <listitem>
          <para>Parameter understood by both the kernel and the system
          and service manager to control console log verbosity. For
          details, see
          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>debug</varname></term>
        <listitem>
          <para>Parameter understood by both the kernel and the system
          and service manager to control console log verbosity. For
          details, see
          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>-b</varname></term>
        <term><varname>rd.emergency</varname></term>
        <term><varname>emergency</varname></term>
        <term><varname>rd.rescue</varname></term>
        <term><varname>rescue</varname></term>
        <term><varname>single</varname></term>
        <term><varname>s</varname></term>
        <term><varname>S</varname></term>
        <term><varname>1</varname></term>
        <term><varname>2</varname></term>
        <term><varname>3</varname></term>
        <term><varname>4</varname></term>
        <term><varname>5</varname></term>
        <listitem>
          <para>Parameters understood by the system and service
          manager, as compatibility and convenience options. For details, see
          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>locale.LANG=</varname></term>
        <term><varname>locale.LANGUAGE=</varname></term>
        <term><varname>locale.LC_CTYPE=</varname></term>
        <term><varname>locale.LC_NUMERIC=</varname></term>
        <term><varname>locale.LC_TIME=</varname></term>
        <term><varname>locale.LC_COLLATE=</varname></term>
        <term><varname>locale.LC_MONETARY=</varname></term>
        <term><varname>locale.LC_MESSAGES=</varname></term>
        <term><varname>locale.LC_PAPER=</varname></term>
        <term><varname>locale.LC_NAME=</varname></term>
        <term><varname>locale.LC_ADDRESS=</varname></term>
        <term><varname>locale.LC_TELEPHONE=</varname></term>
        <term><varname>locale.LC_MEASUREMENT=</varname></term>
        <term><varname>locale.LC_IDENTIFICATION=</varname></term>
        <listitem>
          <para>Parameters understood by the system and service
          manager to control locale and language settings. For
          details, see
          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>fsck.mode=</varname></term>
        <term><varname>fsck.repair=</varname></term>

        <listitem>
          <para>Parameters understood by the file system checker
          services. For details, see
          <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>quotacheck.mode=</varname></term>

        <listitem>
          <para>Parameter understood by the file quota checker
          service. For details, see
          <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.journald.forward_to_syslog=</varname></term>
        <term><varname>systemd.journald.forward_to_kmsg=</varname></term>
        <term><varname>systemd.journald.forward_to_console=</varname></term>
        <term><varname>systemd.journald.forward_to_wall=</varname></term>

        <listitem>
          <para>Parameters understood by the journal service. For
          details, see
          <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>vconsole.keymap=</varname></term>
        <term><varname>vconsole.keymap_toggle=</varname></term>
        <term><varname>vconsole.font=</varname></term>
        <term><varname>vconsole.font_map=</varname></term>
        <term><varname>vconsole.font_unimap=</varname></term>

        <listitem>
          <para>Parameters understood by the virtual console setup logic. For details, see
          <citerefentry><refentrytitle>vconsole.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>udev.log_priority=</varname></term>
        <term><varname>rd.udev.log_priority=</varname></term>
        <term><varname>udev.children_max=</varname></term>
        <term><varname>rd.udev.children_max=</varname></term>
        <term><varname>udev.exec_delay=</varname></term>
        <term><varname>rd.udev.exec_delay=</varname></term>
        <term><varname>udev.event_timeout=</varname></term>
        <term><varname>rd.udev.event_timeout=</varname></term>
        <term><varname>net.ifnames=</varname></term>

        <listitem>
          <para>Parameters understood by the device event managing
          daemon. For details, see
          <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>plymouth.enable=</varname></term>

        <listitem>
          <para>May be used to disable the Plymouth boot splash. For
          details, see
          <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>luks=</varname></term>
        <term><varname>rd.luks=</varname></term>
        <term><varname>luks.crypttab=</varname></term>
        <term><varname>rd.luks.crypttab=</varname></term>
        <term><varname>luks.name=</varname></term>
        <term><varname>rd.luks.name=</varname></term>
        <term><varname>luks.uuid=</varname></term>
        <term><varname>rd.luks.uuid=</varname></term>
        <term><varname>luks.options=</varname></term>
        <term><varname>rd.luks.options=</varname></term>
        <term><varname>luks.key=</varname></term>
        <term><varname>rd.luks.key=</varname></term>

        <listitem>
          <para>Configures the LUKS full-disk encryption logic at
          boot. For details, see
          <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>fstab=</varname></term>
        <term><varname>rd.fstab=</varname></term>

        <listitem>
          <para>Configures the <filename>/etc/fstab</filename> logic
          at boot. For details, see
          <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>root=</varname></term>
        <term><varname>rootfstype=</varname></term>
        <term><varname>rootflags=</varname></term>
        <term><varname>ro</varname></term>
        <term><varname>rw</varname></term>

        <listitem>
          <para>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-writable initially. For details,
          see
          <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>mount.usr=</varname></term>
        <term><varname>mount.usrfstype=</varname></term>
        <term><varname>mount.usrflags=</varname></term>

        <listitem>
          <para>Configures the /usr file system (if required) and
          its file system type and mount options. For details, see
          <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>roothash=</varname></term>
        <term><varname>systemd.verity=</varname></term>
        <term><varname>rd.systemd.verity=</varname></term>
        <term><varname>systemd.verity_root_data=</varname></term>
        <term><varname>systemd.verity_root_hash=</varname></term>
        <listitem>
          <para>Configures the integrity protection root hash for the root file system, and other related
          parameters. For details, see
          <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.gpt_auto=</varname></term>
        <term><varname>rd.systemd.gpt_auto=</varname></term>

        <listitem>
          <para>Configures whether GPT based partition auto-discovery
          shall be attempted. For details, see
          <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.default_timeout_start_sec=</varname></term>

        <listitem>
          <para>Overwrites the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at boot. For details,
          see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.watchdog_device=</varname></term>

        <listitem>
          <para>Overwrites the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>modules_load=</varname></term>
        <term><varname>rd.modules_load=</varname></term>

        <listitem>
          <para>Load a specific kernel module early at boot. For
          details, see
          <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>resume=</varname></term>

        <listitem>
          <para>Enables resume from hibernation using the specified
          device. All
          <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>-like
          paths are supported. For details, see
          <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>systemd.firstboot=</varname></term>

        <listitem><para>Takes a boolean argument, defaults to on. If off,
        <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        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.</para></listitem>
      </varlistentry>
    </variablelist>

  </refsect1>

  <refsect1>
      <title>See Also</title>
      <para>
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>bootparam</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>dracut.cmdline</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-fsck@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-quotacheck.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-vconsole-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry project='die-net'><refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-hibernate-resume-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-firstboot.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
      </para>
  </refsect1>

</refentry>