systemd.timer — systemd timer configuration files
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.
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 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 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.
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.
systemd(1), systemctl(8), systemd.unit(5), systemd.service(5)