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SYSTEMD.TIMER(5) | systemd.timer | SYSTEMD.TIMER(5) |
NAME¶
systemd.timer - Timer unit configurationSYNOPSIS¶
timer.timerDESCRIPTION¶
A unit configuration file whose name ends in ".timer" encodes information about a timer controlled and supervised by systemd, for timer-based activation. This man page lists the configuration options specific to this unit type. See systemd.unit(5) 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. 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 foo.timer activates a matching service foo.service. The unit to activate may be controlled by Unit= (see below). Unless DefaultDependencies= is set to false, timer units will implicitly have dependencies of type Conflicts= and Before= on shutdown.target. 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.OPTIONS¶
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: OnActiveSec=, OnBootSec=, OnStartupSec=, OnUnitActiveSec=, OnUnitInactiveSec=Defines monotonic timers relative to different starting
points: OnActiveSec= defines a timer relative to the moment the timer
itself is activated. OnBootSec= defines a timer relative to when the
machine was booted up. OnStartupSec= defines a timer relative to when
systemd was first started. OnUnitActiveSec= defines a timer relative to
when the unit the timer is activating was last activated.
OnUnitInactiveSec= defines a timer relative to when the unit the timer
is activating was last deactivated.
Multiple directives may be combined of the same and of different types. For
example, by combining OnBootSec= and OnUnitActiveSec=, it is
possible to define a timer that elapses in regular intervals and activates a
specific service each time.
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
systemd.unit(5).
If a timer configured with OnBootSec= or OnStartupSec= 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.
These are monotonic timers, independent of wall-clock time and timezones. If the
computer is temporarily suspended, the monotonic clock stops too.
If the empty string is assigned to any of these options, the list of timers is
reset, and all prior assignments will have no effect.
Note that timers do not necessarily expire at the precise time configured with
these settings, as they are subject to the AccuracySec= setting
below.
OnCalendar=
Defines realtime (i.e. wallclock) timers with calendar
event expressions. See systemd.time(7) for more information on the
syntax of calendar event expressions. Otherwise, the semantics are similar to
OnActiveSec= and related settings.
Note that timers do not necessarily expire at the precise time configured with
this setting, as it is subject to the AccuracySec= setting below.
AccuracySec=
Specify the accuracy the timer shall elapse with.
Defaults to 1min. The timer is scheduled to elapse within a time window
starting with the time specified in OnCalendar=, OnActiveSec=,
OnBootSec=, OnStartupSec=, OnUnitActiveSec= or
OnUnitInactiveSec= and ending the time configured with
AccuracySec= later. Within this time window, the expiry time will be
placed at a host-specific, randomized but stable position that is synchronized
between all local timer units. This is done in order to distribute the wake-up
time in networked installations, as well as optimizing power consumption to
suppress unnecessary CPU wake-ups. To get best accuracy, set this option to
1us. Note that the timer is still subject to the timer slack configured via
systemd-system.conf(5)'s TimerSlackNSec= setting. See
prctl(2) for details. To optimize power consumption, make sure to set
this value as high as possible and as low as necessary.
Unit=
The unit to activate when this timer elapses. The
argument is a unit name, whose suffix is not ".timer". 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.
Persistent=
Takes a boolean argument. If true, the time when the
service unit was last triggered is stored on disk. When the timer is
activated, the service unit is triggered immediately if it would have been
triggered at least once during the time when the timer was inactive. This is
useful to catch up on missed runs of the service when the machine was off.
Note that this setting only has an effect on timers configured with
OnCalendar=.
WakeSystem=
Takes a boolean argument. If true, an elapsing timer will
cause the system to resume from suspend, should it be suspended and if the
system supports this. Note that this option will only make sure the system
resumes on the appropriate times, it will not take care of suspending it again
after any work that is to be done is finished. Defaults to false.
SEE ALSO¶
systemd(1), systemctl(1), systemd.unit(5), systemd.service(5), systemd.time(7), systemd.directives(7), systemd-system.conf(5), prctl(2)systemd 215 |