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</style><a href="index.html">Index </a>·
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<a href="systemd.directives.html">Directives </a>·
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<a href="../python-systemd/index.html">Python </a>·
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<a href="../libudev/index.html">libudev </a>·
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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 217</span><hr><div class="refentry"><a name="systemd.timer"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>systemd.timer — Timer unit configuration</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename"><em class="replaceable"><code>timer</code></em>.timer</code></p></div><div class="refsect1"><a name="idm214169044224"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p>A unit configuration file whose name ends in
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"<code class="literal">.timer</code>" encodes information about
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a timer controlled and supervised by systemd, for
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timer-based activation.</p><p>This man page lists the configuration options
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specific to this unit type. See
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<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
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for the common options of all unit configuration
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files. The common configuration items are configured
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in the generic [Unit] and [Install] sections. The
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timer specific configuration options are configured in
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the [Timer] section.</p><p>For each timer file, a matching unit file must
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exist, describing the unit to activate when the timer
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elapses. By default, a service by the same name as the
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timer (except for the suffix) is activated. Example: a
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timer file <code class="filename">foo.timer</code> activates a
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matching service <code class="filename">foo.service</code>. The
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unit to activate may be controlled by
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<code class="varname">Unit=</code> (see below).</p><p>Unless <code class="varname">DefaultDependencies=</code>
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is set to <code class="option">false</code>, all timer units will
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implicitly have dependencies of type
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<code class="varname">Conflicts=</code> and
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<code class="varname">Before=</code> on
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<code class="filename">shutdown.target</code> to ensure that
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they are stopped cleanly prior to system shutdown.
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Timer units with at least one
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<code class="varname">OnCalendar=</code> directive will have an
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additional <code class="varname">After=</code> dependency on
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<code class="filename">timer-sync.target</code> to avoid
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being started before the system clock has been
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correctly set. Only timer units involved with early
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boot or late system shutdown should disable the
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<code class="varname">DefaultDependencies=</code> option.</p></div><div class="refsect1"><a name="idm214169032768"></a><h2 id="Options">Options<a class="headerlink" title="Permalink to this headline" href="#Options">¶</a></h2><p>Timer files must include a [Timer] section,
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which carries information about the timer it
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defines. The options specific to the [Timer] section
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of timer units are the following:</p><div class="variablelist"><dl class="variablelist"><dt id="OnActiveSec="><span class="term"><code class="varname">OnActiveSec=</code>, </span><span class="term"><code class="varname">OnBootSec=</code>, </span><span class="term"><code class="varname">OnStartupSec=</code>, </span><span class="term"><code class="varname">OnUnitActiveSec=</code>, </span><span class="term"><code class="varname">OnUnitInactiveSec=</code></span><a class="headerlink" title="Permalink to this term" href="#OnActiveSec=">¶</a></dt><dd><p>Defines monotonic timers
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relative to different starting points:
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<code class="varname">OnActiveSec=</code> defines a
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timer relative to the moment the timer
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itself is
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activated. <code class="varname">OnBootSec=</code>
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defines a timer relative to when the
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machine was booted
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up. <code class="varname">OnStartupSec=</code>
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defines a timer relative to when
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systemd was first
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started. <code class="varname">OnUnitActiveSec=</code>
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defines a timer relative to when the
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unit the timer is activating was last
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activated. <code class="varname">OnUnitInactiveSec=</code>
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defines a timer relative to when the
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unit the timer is activating was last
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deactivated.</p><p>Multiple directives may be
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combined of the same and of different
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types. For example, by combining
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<code class="varname">OnBootSec=</code> and
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<code class="varname">OnUnitActiveSec=</code>, it is
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possible to define a timer that
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elapses in regular intervals and
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activates a specific service each
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time.</p><p>The arguments to the directives
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are time spans configured in
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seconds. Example: "OnBootSec=50" means
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50s after boot-up. The argument may
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also include time units. Example:
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"OnBootSec=5h 30min" means 5 hours and
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30 minutes after boot-up. For details
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about the syntax of time spans, see
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<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.</p><p>If a timer configured with
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<code class="varname">OnBootSec=</code> or
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<code class="varname">OnStartupSec=</code> is
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already in the past when the timer
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unit is activated, it will immediately
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elapse and the configured unit is
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started. This is not the case for
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timers defined in the other
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directives.</p><p>These are monotonic timers,
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independent of wall-clock time and timezones. If the
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computer is temporarily suspended, the
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monotonic clock stops too.</p><p>If the empty string is assigned
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to any of these options, the list of
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timers is reset, and all prior
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assignments will have no
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effect.</p><p>Note that timers do not
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necessarily expire at the precise
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time configured with these settings,
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as they are subject to the
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<code class="varname">AccuracySec=</code>
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setting below.</p></dd><dt id="OnCalendar="><span class="term"><code class="varname">OnCalendar=</code></span><a class="headerlink" title="Permalink to this term" href="#OnCalendar=">¶</a></dt><dd><p>Defines realtime
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(i.e. wallclock) timers with calendar
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event expressions. See
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<a href="systemd.time.html"><span class="citerefentry"><span class="refentrytitle">systemd.time</span>(7)</span></a>
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for more information on the syntax of
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calendar event expressions. Otherwise,
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the semantics are similar to
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<code class="varname">OnActiveSec=</code> and
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related settings.</p><p>Note that timers do not
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necessarily expire at the precise
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time configured with this setting,
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as it is subject to the
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<code class="varname">AccuracySec=</code>
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setting below.</p></dd><dt id="AccuracySec="><span class="term"><code class="varname">AccuracySec=</code></span><a class="headerlink" title="Permalink to this term" href="#AccuracySec=">¶</a></dt><dd><p>Specify the accuracy
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the timer shall elapse with. Defaults
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to 1min. The timer is scheduled to
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elapse within a time window starting
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with the time specified in
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<code class="varname">OnCalendar=</code>,
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<code class="varname">OnActiveSec=</code>,
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<code class="varname">OnBootSec=</code>,
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<code class="varname">OnStartupSec=</code>,
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<code class="varname">OnUnitActiveSec=</code> or
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<code class="varname">OnUnitInactiveSec=</code>
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and ending the time configured with
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<code class="varname">AccuracySec=</code>
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later. Within this time window, the
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expiry time will be placed at a
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host-specific, randomized but stable
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position that is synchronized between
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all local timer units. This is done in
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order to distribute the wake-up time
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in networked installations, as well as
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optimizing power consumption to
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suppress unnecessary CPU wake-ups. To
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get best accuracy, set this option to
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1us. Note that the timer is still
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subject to the timer slack configured
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via
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<a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>'s
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<code class="varname">TimerSlackNSec=</code>
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setting. See
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<a href="http://man7.org/linux/man-pages/man2/prctl.2.html"><span class="citerefentry"><span class="refentrytitle">prctl</span>(2)</span></a>
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for details. To optimize power
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consumption, make sure to set this
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value as high as possible and as low
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as necessary.</p></dd><dt id="Unit="><span class="term"><code class="varname">Unit=</code></span><a class="headerlink" title="Permalink to this term" href="#Unit=">¶</a></dt><dd><p>The unit to activate
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when this timer elapses. The argument is a
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unit name, whose suffix is not
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"<code class="literal">.timer</code>". If not
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specified, this value defaults to a
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service that has the same name as the
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timer unit, except for the
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suffix. (See above.) It is recommended
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that the unit name that is activated
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and the unit name of the timer unit
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are named identically, except for the
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suffix.</p></dd><dt id="Persistent="><span class="term"><code class="varname">Persistent=</code></span><a class="headerlink" title="Permalink to this term" href="#Persistent=">¶</a></dt><dd><p>Takes a boolean
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argument. If true, the time when the
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service unit was last triggered is
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stored on disk. When the timer is
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activated, the service unit is
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triggered immediately if it would have
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been triggered at least once during
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the time when the timer was inactive.
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This is useful to catch up on missed
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runs of the service when the machine
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was off. Note that this setting only
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has an effect on timers configured
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with <code class="varname">OnCalendar=</code>.
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</p></dd><dt id="WakeSystem="><span class="term"><code class="varname">WakeSystem=</code></span><a class="headerlink" title="Permalink to this term" href="#WakeSystem=">¶</a></dt><dd><p>Takes a boolean
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argument. If true, an elapsing timer
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will cause the system to resume from
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suspend, should it be suspended and if
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the system supports this. Note that
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this option will only make sure the
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system resumes on the appropriate
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times, it will not take care of
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suspending it again after any work
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that is to be done is
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finished. Defaults to
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<code class="varname">false</code>.</p></dd></dl></div></div><div class="refsect1"><a name="idm214172940672"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>,
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<a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>,
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<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>,
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<a href="systemd.time.html"><span class="citerefentry"><span class="refentrytitle">systemd.time</span>(7)</span></a>,
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<a href="systemd.directives.html"><span class="citerefentry"><span class="refentrytitle">systemd.directives</span>(7)</span></a>,
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<a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>,
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<a href="http://man7.org/linux/man-pages/man2/prctl.2.html"><span class="citerefentry"><span class="refentrytitle">prctl</span>(2)</span></a>
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</p></div></div></body></html>
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