man/systemd.timer.xml

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

        <refnamediv>
                <refname>systemd.timer</refname>
                <refpurpose>Timer unit configuration</refpurpose>
        </refnamediv>

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

        <refsect1>
                <title>Description</title>

                <para>A unit configuration file whose name ends in
                <filename>.timer</filename> encodes information about
                a timer controlled and supervised by systemd, for
                timer-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
                timer specific configuration options are configured in
                the [Timer] section.</para>

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

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

        <refsect1>
                <title>Options</title>

                <para>Timer files must include a [Timer] section,
                which carries information about the timer it
                defines. The options specific to the [Timer] section
                of timer units are the following:</para>

                <variablelist>
                        <varlistentry>
                                <term><varname>OnActiveSec=</varname></term>
                                <term><varname>OnBootSec=</varname></term>
                                <term><varname>OnStartupSec=</varname></term>
                                <term><varname>OnUnitActiveSec=</varname></term>
                                <term><varname>OnUnitInactiveSec=</varname></term>

                                <listitem><para>Defines timers
                                relative to different starting points:
                                <varname>OnActiveSec=</varname> defines a
                                timer relative to the moment the timer
                                itself is
                                activated. <varname>OnBootSec=</varname>
                                defines a timer relative to when the
                                machine was booted
                                up. <varname>OnStartupSec=</varname>
                                defines a timer relative to when
                                systemd was
                                started. <varname>OnUnitActiveSec=</varname>
                                defines a timer relative to when the
                                unit the timer is activating was last
                                activated. <varname>OnUnitInactiveSec=</varname>
                                defines a timer relative to when the
                                unit the timer is activating was last
                                deactivated.</para>

                                <para>Multiple directives may be
                                combined of the same and of different
                                types. For example, by combining
                                <varname>OnBootSec=</varname> and
                                <varname>OnUnitActiveSec=</varname> it is
                                possible to define a timer that
                                elapses in regular intervals and
                                activates a specific service each
                                time.</para>

                                <para>The arguments to the directives
                                are time spans configured in
                                seconds. Example: "OnBootSec=50" means
                                50s after boot-up. The argument may
                                also include time units. Example:
                                "OnBootSec=5h 30min" means 5 hours and 30
                                minutes after boot-up. For details
                                about the syntax of time spans see
                                <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

                                <para>If a timer configured with
                                <varname>OnBootSec=</varname> or
                                <varname>OnStartupSec=</varname> is
                                already in the past when the timer
                                unit is activated, it will immediately
                                elapse and the configured unit is
                                started. This is not the case for
                                timers defined in the other
                                directives.</para></listitem>

                                <para>These are monotonic timers,
                                independent of wall-clock time and timezones. If the
                                computer is temporarily suspended, the
                                monotonic clock stops too.</para>

                        </varlistentry>
                        <varlistentry>
                                <term><varname>Unit=</varname></term>

                                <listitem><para>The unit to activate
                                when this timer elapses. The argument is a
                                unit name, whose suffix is not
                                <filename>.timer</filename>. If not
                                specified, this value defaults to a
                                service that has the same name as the
                                timer unit, except for the
                                suffix. (See above.) It is recommended
                                that the unit name that is activated
                                and the unit name of the timer unit
                                are named identically, 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>
                  </para>
        </refsect1>

</refentry>