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>Path unit configuration</refpurpose>
        </refnamediv>

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

        <refsect1>
                <title>Description</title>

                <para>A unit configuration file whose name ends in
                <literal>.path</literal> 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 a 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=false</varname>
                is used, 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 class='unit-directives'>
                        <varlistentry>
                                <term><varname>PathExists=</varname></term>
                                <term><varname>PathExistsGlob=</varname></term>
                                <term><varname>PathChanged=</varname></term>
                                <term><varname>PathModified=</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>PathExistsGlob=</varname>
                                works similar, but checks for the
                                existence of at least one file
                                matching the globbing pattern
                                specified. <varname>PathChanged=</varname>
                                may be used to watch a file or
                                directory and activate the configured
                                unit whenever it changes. It is not
                                activated on every write to the
                                watched file but it is activated if
                                the file which was open for writing
                                gets
                                closed. <varname>PathModified=</varname>
                                is similar, but additionally it is
                                activated also on simple writes to the
                                watched file.
                                <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. If the
                                empty string is assigned to any of
                                these options, the list of paths to
                                watch is reset, and any prior
                                assignments of these options will not
                                have any effect.</para>

                                <para>If a path already exists
                                (in case of
                                <varname>PathExists=</varname> and
                                <varname>PathExistsGlob=</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> and
                                <varname>PathModified=</varname>.</para>

                                <para>If the path itself or any of the
                                containing directories are not
                                accessible, <command>systemd</command>
                                will watch for permission changes and
                                notice that conditions are satisfied
                                when permissions allow that.
                                </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
                                <literal>.path</literal>. 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>
                        <varlistentry>
                                <term><varname>MakeDirectory=</varname></term>

                                <listitem><para>Takes a boolean
                                argument. If true, the directories to
                                watch are created before
                                watching. This option is ignored for
                                <varname>PathExists=</varname>
                                settings. Defaults to
                                <option>false</option>.</para></listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><varname>DirectoryMode=</varname></term>

                                <listitem><para>If
                                <varname>MakeDirectory=</varname> is
                                enabled, use the mode specified here to
                                create the directories in
                                question. Takes an access mode in
                                octal notation. Defaults to
                                <option>0755</option>.</para></listitem>
                        </varlistentry>
                </variablelist>
        </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.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                          <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                  </para>
        </refsect1>

</refentry>