systemd/man/systemd.path.xml

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

        <refnamediv>
                <refname>systemd.path</refname>
                <refpurpose>systemd path configuration files</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <para><filename>systemd.path</filename></para>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para>A unit configuration file whose name ends in
                <filename>.path</filename> encodes information about
                a path monitored by systemd, for
                path-based activation.</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
                path specific configuration options are configured in
                the [Path] section.</para>

                <para>For each path file, a matching unit file must
                exist, describing the unit to activate when the path
                changes. By default, a service by the same name as the
                path (except for the suffix) is activated. Example: a
                path file <filename>foo.path</filename> activates a
                matching service <filename>foo.service</filename>. The
                unit to activate may be controlled by
                <varname>Unit=</varname> (see below).</para>

                <para>Internally, path units use the
                <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                API to monitor file systems. Due to that, it suffers by the
                same limitations as inotify, and for example cannot be
                used to monitor files or directories changed by other
                machines on remote NFS file systems.</para>

                <para>If an path unit is beneath another mount
                point in the file system hierarchy, a dependency
                between both units is created automatically.</para>

                <para>Unless <varname>DefaultDependencies=</varname>
                is set to <option>false</option>, path units will
                implicitly have dependencies of type
                <varname>Conflicts=</varname> and
                <varname>Before=</varname> on
                <filename>shutdown.target</filename>. These ensure
                that path units are terminated cleanly prior to system
                shutdown. Only path units involved with early boot or
                late system shutdown should disable this
                option.</para>
        </refsect1>

        <refsect1>
                <title>Options</title>

                <para>Path files must include a [Path] section,
                which carries information about the path(s) it
                monitors. The options specific to the [Path] section
                of path units are the following:</para>

                <variablelist>
                        <varlistentry>
                                <term><varname>PathExists=</varname></term>
                                <term><varname>PathChanged=</varname></term>
                                <term><varname>DirectoryNotEmpty=</varname></term>

                                <listitem><para>Defines paths to
                                monitor for certain changes:
                                <varname>PathExists=</varname> may be
                                used to watch the mere existence of a
                                file or directory. If the file
                                specified exists the configured unit
                                is
                                activated. <varname>PathChanged=</varname>
                                may be used to watch a file or
                                directory and activate the configured
                                unit whenever it changes or is
                                modified. <varname>DirectoryNotEmpty=</varname>
                                may be used to watch a directory and
                                activate the configured unit whenever
                                it contains at least one file.</para>

                                <para>The arguments of these
                                directives must be absolute file
                                system paths.</para>

                                <para>Multiple directives may be
                                combined, of the same and of different
                                types, to watch multiple paths.</para>

                                <para>If a path is already existing
                                (in case of
                                <varname>PathExists=</varname>) or a
                                directory already is not empty (in
                                case of
                                <varname>DirectoryNotEmpty=</varname>)
                                at the time the path unit is activated,
                                then the configured unit is
                                immediately activated as
                                well. Something similar does not apply
                                to <varname>PathChanged=</varname>.
                                </para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>Unit=</varname></term>

                                <listitem><para>The unit to activate
                                when any of the configured paths
                                changes. The argument is a unit name,
                                whose suffix is not
                                <filename>.path</filename>. If not
                                specified, this value defaults to a
                                service that has the same name as the
                                path unit, except for the suffix. (See
                                above.) It is recommended that the
                                unit name that is activated and the
                                unit name of the path unit are named
                                identical, except for the
                                suffix.</para></listitem>
                        </varlistentry>
                </variablelist>
        </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.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                  </para>
        </refsect1>

</refentry>