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diff --git a/man/systemd.timer.xml b/man/systemd.timer.xml
index 659bc81cc..98d4f7b7b 100644
--- a/man/systemd.timer.xml
+++ b/man/systemd.timer.xml
@@ -141,7 +141,7 @@
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
+ about the syntax of time spans, see
systemd.unit5.
If a timer configured with
@@ -163,7 +163,14 @@
to any of these options, the list of
timers is reset, and all prior
assignments will have no
- effect.
+ 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.
@@ -171,16 +178,61 @@
OnCalendar=
Defines realtime
- (i.e. wallclock) timers via calendar
+ (i.e. wallclock) timers with calendar
event expressions. See
systemd.time7
for more information on the syntax of
- calendar event expressions. Otherwise
+ calendar event expressions. Otherwise,
the semantics are similar to
OnActiveSec= and
- related settings.
+ 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.conf5's
+ TimerSlackNSec=
+ setting. See
+ prctl2
+ for details. To optimize power
+ consumption, make sure to set this
+ value as high as possible and as low
+ as necessary.
+
Unit=
@@ -208,7 +260,9 @@
systemd.unit5,
systemd.service5,
systemd.time7,
- systemd.directives7
+ systemd.directives7,
+ systemd-system.conf5,
+ prctl2