man/systemd.timer.xml

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  25 <refentry id="systemd.timer">
  26         <refentryinfo>
  27                 <title>systemd.timer</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.timer</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.timer</refname>
  47                 <refpurpose>Timer unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>systemd.timer</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <filename>.timer</filename> encodes information about
  59                 a timer controlled and supervised by systemd, for
  60                 timer-based activation.</para>
  61
  62                 <para>This man page lists the configuration options
  63                 specific to this unit type. See
  64                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  65                 for the common options of all unit configuration
  66                 files. The common configuration items are configured
  67                 in the generic [Unit] and [Install] sections. The
  68                 timer specific configuration options are configured in
  69                 the [Timer] section.</para>
  70
  71                 <para>For each timer file, a matching unit file must
  72                 exist, describing the unit to activate when the timer
  73                 elapses. By default, a service by the same name as the
  74                 timer (except for the suffix) is activated. Example: a
  75                 timer file <filename>foo.timer</filename> activates a
  76                 matching service <filename>foo.service</filename>. The
  77                 unit to activate may be controlled by
  78                 <varname>Unit=</varname> (see below).</para>
  79
  80                 <para>Unless <varname>DefaultDependencies=</varname>
  81                 is set to <option>false</option>, timer units will
  82                 implicitly have dependencies of type
  83                 <varname>Conflicts=</varname> and
  84                 <varname>Before=</varname> on
  85                 <filename>shutdown.target</filename>. These ensure
  86                 that timer units are stopped cleanly prior to system
  87                 shutdown. Only timer units involved with early boot or
  88                 late system shutdown should disable this
  89                 option.</para>
  90         </refsect1>
  91
  92         <refsect1>
  93                 <title>Options</title>
  94
  95                 <para>Timer files must include a [Timer] section,
  96                 which carries information about the timer it
  97                 defines. The options specific to the [Timer] section
  98                 of timer units are the following:</para>
  99
 100                 <variablelist>
 101                         <varlistentry>
 102                                 <term><varname>OnActiveSec=</varname></term>
 103                                 <term><varname>OnBootSec=</varname></term>
 104                                 <term><varname>OnStartupSec=</varname></term>
 105                                 <term><varname>OnUnitActiveSec=</varname></term>
 106                                 <term><varname>OnUnitInactiveSec=</varname></term>
 107
 108                                 <listitem><para>Defines monotonic timers
 109                                 relative to different starting points:
 110                                 <varname>OnActiveSec=</varname> defines a
 111                                 timer relative to the moment the timer
 112                                 itself is
 113                                 activated. <varname>OnBootSec=</varname>
 114                                 defines a timer relative to when the
 115                                 machine was booted
 116                                 up. <varname>OnStartupSec=</varname>
 117                                 defines a timer relative to when
 118                                 systemd was first
 119                                 started. <varname>OnUnitActiveSec=</varname>
 120                                 defines a timer relative to when the
 121                                 unit the timer is activating was last
 122                                 activated. <varname>OnUnitInactiveSec=</varname>
 123                                 defines a timer relative to when the
 124                                 unit the timer is activating was last
 125                                 deactivated.</para>
 126
 127                                 <para>Multiple directives may be
 128                                 combined of the same and of different
 129                                 types. For example, by combining
 130                                 <varname>OnBootSec=</varname> and
 131                                 <varname>OnUnitActiveSec=</varname> it is
 132                                 possible to define a timer that
 133                                 elapses in regular intervals and
 134                                 activates a specific service each
 135                                 time.</para>
 136
 137                                 <para>The arguments to the directives
 138                                 are time spans configured in
 139                                 seconds. Example: "OnBootSec=50" means
 140                                 50s after boot-up. The argument may
 141                                 also include time units. Example:
 142                                 "OnBootSec=5h 30min" means 5 hours and
 143                                 30 minutes after boot-up. For details
 144                                 about the syntax of time spans see
 145                                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 146
 147                                 <para>If a timer configured with
 148                                 <varname>OnBootSec=</varname> or
 149                                 <varname>OnStartupSec=</varname> is
 150                                 already in the past when the timer
 151                                 unit is activated, it will immediately
 152                                 elapse and the configured unit is
 153                                 started. This is not the case for
 154                                 timers defined in the other
 155                                 directives.</para>
 156
 157                                 <para>These are monotonic timers,
 158                                 independent of wall-clock time and timezones. If the
 159                                 computer is temporarily suspended, the
 160                                 monotonic clock stops too.</para>
 161
 162                                 <para>If the empty string is assigned
 163                                 to any of these options the list of
 164                                 timers is reset, and all prior
 165                                 assignments will have no
 166                                 effect.</para></listitem>
 167
 168                         </varlistentry>
 169
 170                         <varlistentry>
 171                                 <term><varname>OnCalendar=</varname></term>
 172
 173                                 <listitem><para>Defines realtime
 174                                 (i.e. wallclock) timers via calendar
 175                                 event expressions. See
 176                                 <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 177                                 for more information on the syntax of
 178                                 calendar event expressions. Otherwise
 179                                 the semantics are similar to
 180                                 <varname>OnActiveSec=</varname> and
 181                                 related settings.</para></listitem>
 182                         </varlistentry>
 183
 184                         <varlistentry>
 185                                 <term><varname>Unit=</varname></term>
 186
 187                                 <listitem><para>The unit to activate
 188                                 when this timer elapses. The argument is a
 189                                 unit name, whose suffix is not
 190                                 <filename>.timer</filename>. If not
 191                                 specified, this value defaults to a
 192                                 service that has the same name as the
 193                                 timer unit, except for the
 194                                 suffix. (See above.) It is recommended
 195                                 that the unit name that is activated
 196                                 and the unit name of the timer unit
 197                                 are named identically, except for the
 198                                 suffix.</para></listitem>
 199                         </varlistentry>
 200                 </variablelist>
 201         </refsect1>
 202
 203         <refsect1>
 204                   <title>See Also</title>
 205                   <para>
 206                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 207                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 208                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 209                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 210                           <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 211                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 212                   </para>
 213         </refsect1>
 214
 215 </refentry>