Systemd/timers: Difference between revisions
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https://man.archlinux.org/man/systemd.timer.5.en "services with RemainAfterExit=yes set (which stay around continuously even after the service's main process exited) are usually not suitable for activation via repetitive timers, as they will only be activated once, and then stay around forever." Tags: Manual revert Visual edit |
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The following example timer runs a systemd unit every 5 minutes which invokes a bash script. | The following example timer runs a systemd unit every 5 minutes which invokes a bash script. | ||
</translate> | </translate> | ||
< | <syntaxhighlight lang="nix"> | ||
systemd.timers."hello-world" = { | systemd.timers."hello-world" = { | ||
wantedBy = [ "timers.target" ]; | wantedBy = [ "timers.target" ]; | ||
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OnBootSec = "5m"; | OnBootSec = "5m"; | ||
OnUnitActiveSec = "5m"; | OnUnitActiveSec = "5m"; | ||
# Alternatively, if you prefer to specify an exact timestamp | |||
# like one does in cron, you can use the `OnCalendar` option | |||
# to specify a calendar event expression. | |||
# Run every Monday at 10:00 AM in the Asia/Kolkata timezone. | |||
#OnCalendar = "Mon *-*-* 10:00:00 Asia/Kolkata"; | |||
Unit = "hello-world.service"; | Unit = "hello-world.service"; | ||
}; | }; | ||
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}; | }; | ||
}; | }; | ||
</syntaxhighlight> | |||
Alternatively here, avoid quotes when calling for the binary and its command options: | |||
<syntaxHighlight lang="nix"> | |||
${pkgs.foo}/bin/foo command-options | |||
</syntaxHighlight> | </syntaxHighlight> | ||
This will yield the same result as running | |||
<syntaxhighlight lang="bash"> | |||
foo command-options | |||
</syntaxhighlight> | |||
in your terminal. | |||
==== Verifying your timestamp for systemd.time ==== | |||
If you do not understand the format that [https://www.freedesktop.org/software/systemd/man/latest/systemd.time.html systemd.time] expects, you can use the <code>systemd-analyze</code>'s <code>calendar</code> sub-command to understand the next ''N'' times when the timer will get triggered. Following is an example:<syntaxhighlight lang="shell-session"> | |||
$ systemd-analyze calendar --iterations=5 "10:00:00" | |||
Original form: 10:00:00 | |||
Normalized form: *-*-* 10:00:00 | |||
Next elapse: Sat 2024-12-07 10:00:00 IST | |||
(in UTC): Sat 2024-12-07 04:30:00 UTC | |||
From now: 33min left | |||
Iteration #2: Sun 2024-12-08 10:00:00 IST | |||
(in UTC): Sun 2024-12-08 04:30:00 UTC | |||
From now: 24h left | |||
Iteration #3: Mon 2024-12-09 10:00:00 IST | |||
(in UTC): Mon 2024-12-09 04:30:00 UTC | |||
From now: 2 days left | |||
Iteration #4: Tue 2024-12-10 10:00:00 IST | |||
(in UTC): Tue 2024-12-10 04:30:00 UTC | |||
From now: 3 days left | |||
Iteration #5: Wed 2024-12-11 10:00:00 IST | |||
(in UTC): Wed 2024-12-11 04:30:00 UTC | |||
From now: 4 days left | |||
</syntaxhighlight> | |||
====Using the <code>systemd.services.<name>.startAt</code> shorthand==== | |||
If you only want a service to execute at an interval and don't plan to configure the timer much more, you can use the <code>systemd.services.<name>.startAt</code> option. This will have the underlying systemd module in nixpkgs create the timer for you, and set its <code>OnCalendar</code> field. Note that the semantics for <code>OnCalendar</code> are different to <code>OnUnitActiveSec</code>. | |||
This example shows the previous <code>hello-world</code> service configured with <code>startAt</code>, running every 5 minutes. | |||
<syntaxHighlight lang="nix"> | |||
systemd.services."hello-world" = { | |||
script = '' | |||
set -eu | |||
${pkgs.coreutils}/bin/echo "Hello World" | |||
''; | |||
serviceConfig = { | |||
Type = "oneshot"; | |||
User = "root"; | |||
}; | |||
startAt = "*:0/5"; | |||
}; | |||
</syntaxHighlight> | |||
====Running timer on a schedule==== | |||
<translate> | <translate> | ||
<!--T:4--> | <!--T:4--> | ||