man/systemd.timer.html

   1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>systemd.timer</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
   2     a.headerlink {
   3       color: #c60f0f;
   4       font-size: 0.8em;
   5       padding: 0 4px 0 4px;
   6       text-decoration: none;
   7       visibility: hidden;
   8     }
   9
  10     a.headerlink:hover {
  11       background-color: #c60f0f;
  12       color: white;
  13     }
  14
  15     h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink {
  16       visibility: visible;
  17     }
  18   </style><a href="index.html">Index </a>·
  19   <a href="systemd.directives.html">Directives </a>·
  20   <a href="../python-systemd/index.html">Python </a>·
  21   <a href="../libudev/index.html">libudev </a>·
  22   <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 218</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="idm140414250923440"></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
  23                 "<code class="literal">.timer</code>" encodes information about
  24                 a timer controlled and supervised by systemd, for
  25                 timer-based activation.</p><p>This man page lists the configuration options
  26                 specific to this unit type. See
  27                 <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>
  28                 for the common options of all unit configuration
  29                 files. The common configuration items are configured
  30                 in the generic [Unit] and [Install] sections. The
  31                 timer specific configuration options are configured in
  32                 the [Timer] section.</p><p>For each timer file, a matching unit file must
  33                 exist, describing the unit to activate when the timer
  34                 elapses. By default, a service by the same name as the
  35                 timer (except for the suffix) is activated. Example: a
  36                 timer file <code class="filename">foo.timer</code> activates a
  37                 matching service <code class="filename">foo.service</code>. The
  38                 unit to activate may be controlled by
  39                 <code class="varname">Unit=</code> (see below).</p><p>Unless <code class="varname">DefaultDependencies=</code>
  40                 is set to <code class="option">false</code>, all timer units will
  41                 implicitly have dependencies of type
  42                 <code class="varname">Conflicts=</code> and
  43                 <code class="varname">Before=</code> on
  44                 <code class="filename">shutdown.target</code> to ensure that
  45                 they are stopped cleanly prior to system shutdown.
  46                 Timer units with at least one
  47                 <code class="varname">OnCalendar=</code> directive will have an
  48                 additional <code class="varname">After=</code> dependency on
  49                 <code class="filename">timer-sync.target</code> to avoid
  50                 being started before the system clock has been
  51                 correctly set. Only timer units involved with early
  52                 boot or late system shutdown should disable the
  53                 <code class="varname">DefaultDependencies=</code> option.</p></div><div class="refsect1"><a name="idm140414250789840"></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,
  54                 which carries information about the timer it
  55                 defines. The options specific to the [Timer] section
  56                 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
  57                                 relative to different starting points:
  58                                 <code class="varname">OnActiveSec=</code> defines a
  59                                 timer relative to the moment the timer
  60                                 itself is
  61                                 activated. <code class="varname">OnBootSec=</code>
  62                                 defines a timer relative to when the
  63                                 machine was booted
  64                                 up. <code class="varname">OnStartupSec=</code>
  65                                 defines a timer relative to when
  66                                 systemd was first
  67                                 started. <code class="varname">OnUnitActiveSec=</code>
  68                                 defines a timer relative to when the
  69                                 unit the timer is activating was last
  70                                 activated. <code class="varname">OnUnitInactiveSec=</code>
  71                                 defines a timer relative to when the
  72                                 unit the timer is activating was last
  73                                 deactivated.</p><p>Multiple directives may be
  74                                 combined of the same and of different
  75                                 types. For example, by combining
  76                                 <code class="varname">OnBootSec=</code> and
  77                                 <code class="varname">OnUnitActiveSec=</code>, it is
  78                                 possible to define a timer that
  79                                 elapses in regular intervals and
  80                                 activates a specific service each
  81                                 time.</p><p>The arguments to the directives
  82                                 are time spans configured in
  83                                 seconds. Example: "OnBootSec=50" means
  84                                 50s after boot-up. The argument may
  85                                 also include time units. Example:
  86                                 "OnBootSec=5h 30min" means 5 hours and
  87                                 30 minutes after boot-up. For details
  88                                 about the syntax of time spans, see
  89                                 <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>.</p><p>If a timer configured with
  90                                 <code class="varname">OnBootSec=</code> or
  91                                 <code class="varname">OnStartupSec=</code> is
  92                                 already in the past when the timer
  93                                 unit is activated, it will immediately
  94                                 elapse and the configured unit is
  95                                 started. This is not the case for
  96                                 timers defined in the other
  97                                 directives.</p><p>These are monotonic timers,
  98                                 independent of wall-clock time and timezones. If the
  99                                 computer is temporarily suspended, the
 100                                 monotonic clock stops too.</p><p>If the empty string is assigned
 101                                 to any of these options, the list of
 102                                 timers is reset, and all prior
 103                                 assignments will have no
 104                                 effect.</p><p>Note that timers do not
 105                                 necessarily expire at the precise
 106                                 time configured with these settings,
 107                                 as they are subject to the
 108                                 <code class="varname">AccuracySec=</code>
 109                                 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
 110                                 (i.e. wallclock) timers with calendar
 111                                 event expressions. See
 112                                 <a href="systemd.time.html"><span class="citerefentry"><span class="refentrytitle">systemd.time</span>(7)</span></a>
 113                                 for more information on the syntax of
 114                                 calendar event expressions. Otherwise,
 115                                 the semantics are similar to
 116                                 <code class="varname">OnActiveSec=</code> and
 117                                 related settings.</p><p>Note that timers do not
 118                                 necessarily expire at the precise
 119                                 time configured with this setting,
 120                                 as it is subject to the
 121                                 <code class="varname">AccuracySec=</code>
 122                                 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
 123                                 the timer shall elapse with. Defaults
 124                                 to 1min. The timer is scheduled to
 125                                 elapse within a time window starting
 126                                 with the time specified in
 127                                 <code class="varname">OnCalendar=</code>,
 128                                 <code class="varname">OnActiveSec=</code>,
 129                                 <code class="varname">OnBootSec=</code>,
 130                                 <code class="varname">OnStartupSec=</code>,
 131                                 <code class="varname">OnUnitActiveSec=</code> or
 132                                 <code class="varname">OnUnitInactiveSec=</code>
 133                                 and ending the time configured with
 134                                 <code class="varname">AccuracySec=</code>
 135                                 later. Within this time window, the
 136                                 expiry time will be placed at a
 137                                 host-specific, randomized but stable
 138                                 position that is synchronized between
 139                                 all local timer units. This is done in
 140                                 order to distribute the wake-up time
 141                                 in networked installations, as well as
 142                                 optimizing power consumption to
 143                                 suppress unnecessary CPU wake-ups. To
 144                                 get best accuracy, set this option to
 145                                 1us. Note that the timer is still
 146                                 subject to the timer slack configured
 147                                 via
 148                                 <a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>'s
 149                                 <code class="varname">TimerSlackNSec=</code>
 150                                 setting. See
 151                                 <a href="http://man7.org/linux/man-pages/man2/prctl.2.html"><span class="citerefentry"><span class="refentrytitle">prctl</span>(2)</span></a>
 152                                 for details. To optimize power
 153                                 consumption, make sure to set this
 154                                 value as high as possible and as low
 155                                 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
 156                                 when this timer elapses. The argument is a
 157                                 unit name, whose suffix is not
 158                                 "<code class="literal">.timer</code>". If not
 159                                 specified, this value defaults to a
 160                                 service that has the same name as the
 161                                 timer unit, except for the
 162                                 suffix. (See above.) It is recommended
 163                                 that the unit name that is activated
 164                                 and the unit name of the timer unit
 165                                 are named identically, except for the
 166                                 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
 167                                 argument. If true, the time when the
 168                                 service unit was last triggered is
 169                                 stored on disk. When the timer is
 170                                 activated, the service unit is
 171                                 triggered immediately if it would have
 172                                 been triggered at least once during
 173                                 the time when the timer was inactive.
 174                                 This is useful to catch up on missed
 175                                 runs of the service when the machine
 176                                 was off. Note that this setting only
 177                                 has an effect on timers configured
 178                                 with <code class="varname">OnCalendar=</code>.
 179                                 </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
 180                                 argument. If true, an elapsing timer
 181                                 will cause the system to resume from
 182                                 suspend, should it be suspended and if
 183                                 the system supports this. Note that
 184                                 this option will only make sure the
 185                                 system resumes on the appropriate
 186                                 times, it will not take care of
 187                                 suspending it again after any work
 188                                 that is to be done is
 189                                 finished. Defaults to
 190                                 <code class="varname">false</code>.</p></dd></dl></div></div><div class="refsect1"><a name="idm140414250943152"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
 191                           <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
 192                           <a href="systemctl.html"><span class="citerefentry"><span class="refentrytitle">systemctl</span>(1)</span></a>,
 193                           <a href="systemd.unit.html"><span class="citerefentry"><span class="refentrytitle">systemd.unit</span>(5)</span></a>,
 194                           <a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>,
 195                           <a href="systemd.time.html"><span class="citerefentry"><span class="refentrytitle">systemd.time</span>(7)</span></a>,
 196                           <a href="systemd.directives.html"><span class="citerefentry"><span class="refentrytitle">systemd.directives</span>(7)</span></a>,
 197                           <a href="systemd-system.conf.html"><span class="citerefentry"><span class="refentrytitle">systemd-system.conf</span>(5)</span></a>,
 198                           <a href="http://man7.org/linux/man-pages/man2/prctl.2.html"><span class="citerefentry"><span class="refentrytitle">prctl</span>(2)</span></a>
 199                   </p></div></div></body></html>