[systemd-devel] timer triggers at unexpected times

[Olaf Hering]

Hello,

the two unit files shown at the end are supposed to run the service
once per week around the specified time. But for some reason the
timer triggers at unexpected other times. What needs to be done
to make sure it really only runs at the specified OnCalendar= time?

Both units are part of a rpm package. The usual %pre/%post systemd
macros are used. It turned out: doing a "rpm -Uvh abc.rpm" does
trigger the timer. But surprisingly, not every time that package
gets updated. The %post script does "systemctl daemon-reload".
The %postun does "systemctl daemon-reload" and
"systemctl try-restart abc.timer".

In other words: at one weekend, or the days around it, when I update
abc.rpm, the timer triggers while rpm (or in fact: zypper) runs. On
another weekend, or the days around it, the timer does not trigger
while rpm runs.

The systemd.timer(5) manual, if I interpret it correctly, gives no
hints why the timer would trigger at times other than the one
specified in the OnCalendar= setting.

Is there a way to enable timer specific debugging, to see why the
timer or its service was started?

This is going on since a year or two already with SLE15SP5 and SP6
and now SP7. The system in question runs currently systemd-254.24.


Thanks,
Olaf


==> rpm/abc.timer <==
# vim: syntax=systemd
[Unit]
Description=timer for abc
[Timer]
OnCalendar=Sat *-*-* 12:34:56 UTC
[Install]
WantedBy=multi-user.target

==> rpm/abc.service <==
# vim: syntax=systemd
[Unit]
Description=service for abc
[Service]
Environment=TZ=UTC
ExecStart=/usr/share/abc/abc.sh
IOSchedulingClass=idle
CPUSchedulingPolicy=batch
PrivateTmp=true
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