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develox
Asked: 2021-03-13 08:23:29 +0800 CST

How to troubleshoot a systemd timer on Ubuntu 16.04 that won't re-schedule every minute as expected?

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I have an existing systemctl target that was originally (by default installation) scheduled to run everyday, almost continuosly with just a pause of 30 seconds between the end and beginning of each run, i.e. with its default /usr/lib/systemd/system/my-unit.timer being:

[Unit]
Description=My Unit description

[Timer]
OnActiveSec=0
OnUnitInactiveSec=30s
Unit=my-unit.target

[Install]
WantedBy=timers.target

Now I got a requirement to restrict the running time window to a range of hours every day. I've had a look around and thought that I could modify the scheduling without altering the existing target/timer, by using the command:

systemctl edit my-unit.timer

which would automatically create an override timer conf in

/etc/systemd/system/my-unit.timer.d/override.conf

I have for example written the following systemd timer associated to a namesake systemd target:

[Timer]
# Disable the default timer
OnUnitInactiveSec=
OnCalendar=*-*-* 17,18:*:00

This, in my understanding, should run everyday, every minute from 17:00 to 18:59. The problem is that it actually runs once the first time I restart the timer. It will start at the expected next minute turn, but won't reschedule the following ones:

NEXT                         LEFT        LAST                         PASSED      UNIT                  ACTIVATES
Fri 2021-03-12 17:20:00 CET  1min 4s ago Fri 2021-03-12 17:20:01 CET  1min 2s ago

this was an example of me restarting the timer slightly before 17:20. The target did run at 17:20 as expected, but then the NEXT didn't update. And it won't until I manually restart the timer. I would pass it through the:

systemd-analyze calendar

command and show its output here if possible, but the calendar command was not available for systemd-analyze in Ubuntu 16.04 yet.

What am I doing or what did I understand wrong ?

As a side question, in case I wanted to use the same "30secs after last run" pattern but limit it to a few hours a day, is it possible to combine monotonic timer specifications (like the above OnUnitInactiveSec) with OnCalendar to say "run on these monotonic pattern, but only during this calendar time-range" ?

ubuntu systemd systemctl ubuntu-16.04

0 Answers