Select the THREE statements that are true about systemd timer units.
LPIC-1 Exam 102-500, objective 107. Administrative tasks medium
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The options
Choose 3.
Correct `systemctl list-timers` shows each active timer's next elapse time and the unit it will activate.
True. It is the standard overview command, and it also reports how long ago each timer last fired.
Correct A timer called backup.timer activates backup.service unless the [Timer] section names a different unit with Unit=.
True. The implicit target is the unit with the same basename and a .service suffix; Unit= overrides that default.
Correct A timer unit has no effect until it is itself started, or enabled so that it starts at boot.
True. The .timer unit is what must be running; enabling or starting the .service it triggers is neither necessary nor sufficient.
Not correct The value of OnCalendar= uses the same five-field syntax as a crontab time specification.
False. systemd uses its own calendar syntax, roughly weekday plus date plus time, as in `Mon..Fri *-*-* 09:00:00`. Crontab's five positional fields are not accepted.
Not correct Timer units are stored in /etc/cron.d/ so that cron and systemd share one schedule.
False. Unit files live under /etc/systemd/system/, /run/systemd/system/ and /usr/lib/systemd/system/. The two schedulers are entirely independent.
Why
A systemd timer is a pair: the .timer unit carries the schedule, the unit it activates carries the work. Because the pairing is by name, a lone .timer with no matching .service fails at activation time. Timers are managed with the ordinary unit verbs, so `systemctl enable --now backup.timer` is the usual way to put one into service.
Where this comes from
- Cited
- manual page systemd.timer(5)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 107 and space the ones you get wrong.
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