systemd/man/systemd.mount.xml

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<refentry id="systemd.mount">
  <refentryinfo>
    <title>systemd.mount</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>systemd.mount</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd.mount</refname>
    <refpurpose>Mount unit configuration</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename><replaceable>mount</replaceable>.mount</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>A unit configuration file whose name ends in
    <literal>.mount</literal> encodes information about a file system
    mount point controlled and supervised by systemd.</para>

    <para>This man page lists the configuration options specific to
    this unit type. See
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for the common options of all unit configuration files. The common
    configuration items are configured in the generic [Unit] and
    [Install] sections. The mount specific configuration options are
    configured in the [Mount] section.</para>

    <para>Additional options are listed in
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    which define the execution environment the
    <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    program is executed in, and in
    <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    which define the way the processes are terminated, and in
    <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
    which configure resource control settings for the processes of the
    service.</para>

    <para>Note that the options <varname>User=</varname> and
    <varname>Group=</varname> are not useful for mount units.
    systemd passes two parameters to
    <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>;
    the values of <varname>What=</varname> and <varname>Where=</varname>.
    When invoked in this way,
    <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    does not read any options from <filename>/etc/fstab</filename>, and
    must be run as UID 0.</para>

    <para>Mount units must be named after the mount point directories they control. Example: the mount point <filename
    noindex='true'>/home/lennart</filename> must be configured in a unit file <filename>home-lennart.mount</filename>.
    For details about the escaping logic used to convert a file system path to a unit name, see
    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.  Note that mount
    units cannot be templated, nor is possible to add multiple names to a mount unit by creating additional symlinks to
    it.</para>

    <para>Optionally, a mount unit may be accompanied by an automount
    unit, to allow on-demand or parallelized mounting. See
    <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

    <para>Mount points created at runtime (independently of unit files
    or <filename>/etc/fstab</filename>) will be monitored by systemd
    and appear like any other mount unit in systemd. See
    <filename>/proc/self/mountinfo</filename> description in
    <citerefentry project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para>Some file systems have special semantics as API file systems
    for kernel-to-userspace and userspace-to-userspace interfaces. Some
    of them may not be changed via mount units, and cannot be
    disabled. For a longer discussion see <ulink
    url="https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems">API
    File Systems</ulink>.</para>
  </refsect1>

  <refsect1>
    <title>Implicit Dependencies</title>

    <para>The following dependencies are implicitly added:</para>

    <itemizedlist>
      <listitem><para>If a mount unit is beneath another mount unit in the file
      system hierarchy, both a requirement dependency and an ordering
      dependency between both units are created automatically.</para></listitem>

      <listitem><para>Block device backed file systems automatically gain
      <varname>BindsTo=</varname> and <varname>After=</varname> type
      dependencies on the device unit encapsulating the block
      device (see below).</para></listitem>

      <listitem><para>If traditional file system quota is enabled for a mount
      unit, automatic <varname>Wants=</varname> and
      <varname>Before=</varname> dependencies on
      <filename>systemd-quotacheck.service</filename> and
      <filename>quotaon.service</filename> are added.</para></listitem>

      <listitem><para>Additional implicit dependencies may be added as result of
      execution and resource control parameters as documented in
      <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
      and
      <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
      </para></listitem>
    </itemizedlist>
  </refsect1>

  <refsect1>
    <title>Default Dependencies</title>

    <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>

    <itemizedlist>
      <listitem><para>All mount units acquire automatic <varname>Before=</varname> and <varname>Conflicts=</varname> on
      <filename>umount.target</filename> in order to be stopped during shutdown.</para></listitem>

      <listitem><para>Mount units referring to local file systems automatically gain
      an <varname>After=</varname> dependency on <filename>local-fs-pre.target</filename>.</para></listitem>

      <listitem><para>Network mount units
      automatically acquire <varname>After=</varname> dependencies on <filename>remote-fs-pre.target</filename>,
      <filename>network.target</filename> and <filename>network-online.target</filename>. Towards the latter a
      <varname>Wants=</varname> unit is added as well.</para></listitem>
    </itemizedlist>

    <para>Mount units referring to local and network file systems are
    distinguished by their file system type specification. In some cases this is not sufficient (for example network
    block device based mounts, such as iSCSI), in which case <option>_netdev</option> may be added to the mount option
    string of the unit, which forces systemd to consider the mount unit a network mount.</para>
  </refsect1>

  <refsect1>
    <title><filename>fstab</filename></title>

    <para>Mount units may either be configured via unit files, or via
    <filename>/etc/fstab</filename> (see
    <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for details). Mounts listed in <filename>/etc/fstab</filename>
    will be converted into native units dynamically at boot and when
    the configuration of the system manager is reloaded. In general,
    configuring mount points through <filename>/etc/fstab</filename>
    is the preferred approach. See
    <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    for details about the conversion.</para>

    <para>The NFS mount option <option>bg</option> for NFS background mounts
    as documented in <citerefentry project='man-pages'><refentrytitle>nfs</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    is detected by <command>systemd-fstab-generator</command> and the options
    are transformed so that systemd fulfills the job-control implications of
    that option.  Specifically <command>systemd-fstab-generator</command> acts
    as though <literal>x-systemd.mount-timout=infinity,retry=10000</literal> was
    prepended to the option list, and <literal>fg,nofail</literal> was appended.
    Depending on specific requirements, it may be appropriate to provide some of
    these options explicitly, or to make use of the
    <literal>x-systemd.automount</literal> option described below instead
    of using <literal>bg</literal>.</para>

    <para>When reading <filename>/etc/fstab</filename> a few special
    mount options are understood by systemd which influence how
    dependencies are created for mount points. systemd will create a
    dependency of type <varname>Wants=</varname> or
    <option>Requires</option> (see option <option>nofail</option>
    below), from either <filename>local-fs.target</filename> or
    <filename>remote-fs.target</filename>, depending whether the file
    system is local or remote.</para>

    <variablelist class='fstab-options'>

      <varlistentry>
        <term><option>x-systemd.requires=</option></term>

        <listitem><para>Configures a <varname>Requires=</varname> and
        an <varname>After=</varname> dependency between the created
        mount unit and another systemd unit, such as a device or mount
        unit. The argument should be a unit name, or an absolute path
        to a device node or mount point.  This option may be specified
        more than once. This option is particularly useful for mount
        point declarations that need an additional device to be around
        (such as an external journal device for journal file systems)
        or an additional mount to be in place (such as an overlay file
        system that merges multiple mount points). See
        <varname>After=</varname> and <varname>Requires=</varname> in
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.before=</option></term>
        <term><option>x-systemd.after=</option></term>

        <listitem><para>Configures a <varname>Before=</varname>
        dependency or <varname>After=</varname> between the created
        mount unit and another systemd unit, such as a mount unit.
        The argument should be a unit name or an absolute path
        to a mount point. This option may be specified more than once.
        This option is particularly useful for mount point declarations
        with <option>nofail</option> option that are mounted
        asynchronously but need to be mounted before or after some unit
        start, for example, before <filename>local-fs.target</filename>
        unit.
        See <varname>Before=</varname> and <varname>After=</varname> in
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.requires-mounts-for=</option></term>

        <listitem><para>Configures a
        <varname>RequiresMountsFor=</varname> dependency between the
        created mount unit and other mount units. The argument must be
        an absolute path. This option may be specified more than once.
        See <varname>RequiresMountsFor=</varname> in
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details.</para></listitem>
       </varlistentry>

      <varlistentry>
        <term><option>x-systemd.device-bound</option></term>

        <listitem><para>The block device backed file system will be upgraded
        to <varname>BindsTo=</varname> dependency. This option is only useful
        when mounting file systems manually with
        <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        as the default dependency in this case is <varname>Requires=</varname>.
        This option is already implied by entries in <filename>/etc/fstab</filename>
        or by mount units.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.automount</option></term>

        <listitem><para>An automount unit will be created for the file
        system. See
        <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.idle-timeout=</option></term>

        <listitem><para>Configures the idle timeout of the
        automount unit. See <varname>TimeoutIdleSec=</varname> in
        <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for details.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.device-timeout=</option></term>

        <listitem><para>Configure how long systemd should wait for a
        device to show up before giving up on an entry from
        <filename>/etc/fstab</filename>. Specify a time in seconds or
        explicitly append a unit such as <literal>s</literal>,
        <literal>min</literal>, <literal>h</literal>,
        <literal>ms</literal>.</para>

        <para>Note that this option can only be used in
        <filename>/etc/fstab</filename>, and will be
        ignored when part of the <varname>Options=</varname>
        setting in a unit file.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.mount-timeout=</option></term>

        <listitem><para>Configure how long systemd should wait for the
        mount command to finish before giving up on an entry from
        <filename>/etc/fstab</filename>. Specify a time in seconds or
        explicitly append a unit such as <literal>s</literal>,
        <literal>min</literal>, <literal>h</literal>,
        <literal>ms</literal>.</para>

        <para>Note that this option can only be used in
        <filename>/etc/fstab</filename>, and will be
        ignored when part of the <varname>Options=</varname>
        setting in a unit file.</para>

        <para>See <varname>TimeoutSec=</varname> below for
        details.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.makefs</option></term>

        <listitem><para>The file system or swap structure will be intialized
        on the device. If the device is not "empty", i.e. it contains any signature,
        the operation will be skipped. It is hence expected that this option
        remains set even after the device has been initalized.</para>

        <para>Note that this option can only be used in
        <filename>/etc/fstab</filename>, and will be ignored when part of the
        <varname>Options=</varname> setting in a unit file.</para>

        <para>See
        <citerefentry><refentrytitle>systemd-makefs@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
        </para>

        <para><citerefentry project='man-pages'><refentrytitle>wipefs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        may be used to remove any signatures from a block device to force
        <option>x-systemd.makefs</option> to reinitialize the device.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-systemd.growfs</option></term>

        <listitem><para>The file system will be grown to occupy the full block
        device. If the file system is already at maximum size, no action will
        be performed. It is hence expected that this option remains set even after
        the file system has been grown. Only certain file system types are supported,
        see
        <citerefentry><refentrytitle>systemd-makefs@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        for details.</para>

        <para>Note that this option can only be used in
        <filename>/etc/fstab</filename>, and will be ignored when part of the
        <varname>Options=</varname> setting in a unit file.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>_netdev</option></term>

        <listitem><para>Normally the file system type is used to determine if a
        mount is a "network mount", i.e. if it should only be started after the
        network is available. Using this option overrides this detection and
        specifies that the mount requires network.</para>

        <para>Network mount units are ordered between <filename>remote-fs-pre.target</filename>
        and <filename>remote-fs.target</filename>, instead of
        <filename>local-fs-pre.target</filename> and <filename>local-fs.target</filename>.
        They also pull in <filename>network-online.target</filename> and are ordered after
        it and <filename>network.target</filename>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>noauto</option></term>
        <term><option>auto</option></term>

        <listitem><para>With <option>noauto</option>, the mount unit will not be added as a dependency for
        <filename>local-fs.target</filename> or <filename>remote-fs.target</filename>. This means that it will not be
        mounted automatically during boot, unless it is pulled in by some other unit. The <option>auto</option> option
        has the opposite meaning and is the default. Note that the <option>noauto</option> option has an effect on the
        mount unit itself only — if <option>x-systemd.automount</option> is used (see above), then the matching
        automount unit will still be pulled in by these targets.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>nofail</option></term>

        <listitem><para>With <option>nofail</option>, this mount will
        be only wanted, not required, by
        <filename>local-fs.target</filename> or
        <filename>remote-fs.target</filename>. This means that the
        boot will continue even if this mount point is not mounted
        successfully.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>x-initrd.mount</option></term>

        <listitem><para>An additional filesystem to be mounted in the
        initramfs. See <filename>initrd-fs.target</filename>
        description in
        <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
        </para></listitem>
      </varlistentry>
    </variablelist>

    <para>If a mount point is configured in both
    <filename>/etc/fstab</filename> and a unit file that is stored
    below <filename>/usr</filename>, the former will take precedence.
    If the unit file is stored below <filename>/etc</filename>, it
    will take precedence. This means: native unit files take
    precedence over traditional configuration files, but this is
    superseded by the rule that configuration in
    <filename>/etc</filename> will always take precedence over
    configuration in <filename>/usr</filename>.</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>Mount files must include a [Mount] section, which carries
    information about the file system mount points it supervises. A
    number of options that may be used in this section are shared with
    other unit types. These options are documented in
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    and
    <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    The options specific to the [Mount] section of mount units are the
    following:</para>

    <variablelist class='unit-directives'>

      <varlistentry>
        <term><varname>What=</varname></term>
        <listitem><para>Takes an absolute path of a device node, file or other resource to mount. See <citerefentry
        project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry> for details. If
        this refers to a device node, a dependency on the respective device unit is automatically created. (See
        <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more
        information.) This option is mandatory. Note that the usual specifier expansion is applied to this setting,
        literal percent characters should hence be written as <literal>%%</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Where=</varname></term>
        <listitem><para>Takes an absolute path of a directory for the
        mount point; in particular, the destination cannot be a symbolic
        link.  If the mount point does not exist at the time of
        mounting, it is created. This string must be reflected in the
        unit filename. (See above.) This option is
        mandatory.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Type=</varname></term>
        <listitem><para>Takes a string for the file system type. See
        <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
        for details. This setting is optional.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>Options=</varname></term>

        <listitem><para>Mount options to use when mounting. This takes a comma-separated list of options. This setting
        is optional. Note that the usual specifier expansion is applied to this setting, literal percent characters
        should hence be written as <literal>%%</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SloppyOptions=</varname></term>

        <listitem><para>Takes a boolean argument. If true, parsing of
        the options specified in <varname>Options=</varname> is
        relaxed, and unknown mount options are tolerated. This
        corresponds with
        <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
        <parameter>-s</parameter> switch. Defaults to
        off.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>LazyUnmount=</varname></term>

        <listitem><para>Takes a boolean argument. If true, detach the
        filesystem from the filesystem hierarchy at time of the unmount
        operation, and clean up all references to the filesystem as
        soon as they are not busy anymore.
        This corresponds with
        <citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
        <parameter>-l</parameter> switch. Defaults to
        off.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ForceUnmount=</varname></term>

        <listitem><para>Takes a boolean argument. If true, force an
        unmount (in case of an unreachable NFS system).
        This corresponds with
        <citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
        <parameter>-f</parameter> switch. Defaults to
        off.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DirectoryMode=</varname></term>
        <listitem><para>Directories of mount points (and any parent
        directories) are automatically created if needed. This option
        specifies the file system access mode used when creating these
        directories. Takes an access mode in octal notation. Defaults
        to 0755.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>TimeoutSec=</varname></term>
        <listitem><para>Configures the time to wait for the mount
        command to finish. If a command does not exit within the
        configured time, the mount will be considered failed and be
        shut down again. All commands still running will be terminated
        forcibly via <constant>SIGTERM</constant>, and after another
        delay of this time with <constant>SIGKILL</constant>. (See
        <option>KillMode=</option> in
        <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
        Takes a unit-less value in seconds, or a time span value such
        as "5min 20s". Pass 0 to disable the timeout logic. The
        default value is set from the manager configuration file's
        <varname>DefaultTimeoutStartSec=</varname>
        variable.</para></listitem>
      </varlistentry>
    </variablelist>

    <para>Check
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    and
    <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for more settings.</para>
  </refsect1>

  <refsect1>
      <title>See Also</title>
      <para>
        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
        <citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
        <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
      </para>
  </refsect1>

</refentry>