mount: tell /bin/mount to never touch /etc/mtab

[thirdparty/systemd.git] / man / systemd.mount.xml

<?xml version='1.0'?> <!--*-nxml-*-->
<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<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><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                binary 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. Note that the User= and
                Group= options are not particularly useful for mount
                units specifying a <literal>Type=</literal> option or
                using configuration not specified in
                <filename>/etc/fstab</filename>;
                <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                will refuse options that are not listed in
                <filename>/etc/fstab</filename> if it is not 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>.</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>If a mount point is beneath another mount point
                in the file system hierarchy, a dependency between both
                units is created automatically.</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><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-userpace interfaces. Some of them may not
                be changed via mount units, and cannot be disabled.
                For a longer discussion see <ulink
                url="http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems">API
                File Systems</ulink>.</para>
        </refsect1>

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

                <para>Mount units may either be configured via unit
                files, or via <filename>/etc/fstab</filename> (see
                <citerefentry><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>When reading <filename>/etc/fstab</filename> a
                few special mount options are understood by systemd
                which influence how dependencies are created for mount
                points from <filename>/etc/fstab</filename>. systemd
                will create a dependency of type
                <option>Wants</option> from either
                <filename>local-fs.target</filename> or
                <filename>remote-fs.target</filename>, depending
                whether the file system is local or remote. If
                <option>x-systemd.automount</option> is set, an
                automount unit will be created for the file
                system. See
                <citerefentry><refentrytitle>systemd.automount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                for details. If
                <option>x-systemd.device-timeout=</option> is
                specified, it may be used to 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 specify a unit as
                <literal>s</literal>, <literal>min</literal>,
                <literal>h</literal>, <literal>ms</literal>.</para>

                <para>If <option>nofail</option> is given, this mount
                will be only wanted, not required, by the
                <filename>local-fs.target</filename>. This means that
                the boot will continue even if this mount point is not
                mounted successfully. Option <option>fail</option> has
                the opposite meaning and is the default.</para>

                <para>If <option>noauto</option> is given, this mount
                will not be added as a dependency for
                <filename>local-fs.target</filename>. This means that
                it will not be mounted automatically during boot,
                unless it is pulled in by some other unit. Option
                <option>auto</option> has the opposite meaning and is
                the default.</para>

                <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><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.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><varname>Where=</varname></term>
                                <listitem><para>Takes an absolute path
                                of a directory of the mount point. 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><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.</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>DefaultTimeoutStart=</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>8</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><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><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>