systemd timers in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a systemd timer?

A systemd timer is a tool in Linux that schedules tasks to run automatically at specific times or intervals, similar to a clock alarm for scripts or commands.

beginner

Which two files are needed to create a systemd timer?

You need a .service file that defines the task to run, and a .timer file that schedules when the task runs.

beginner

How do you start and enable a systemd timer named backup.timer?

Use sudo systemctl start backup.timer to start it now, and sudo systemctl enable backup.timer to make it start automatically on boot.

intermediate

What does the OnCalendar= setting do in a systemd timer file?

It sets the schedule for when the timer triggers, using calendar events like daily, weekly, or specific dates and times.

beginner

How can you check the status and last run time of a systemd timer?

Run systemctl status yourtimer.timer to see if it is active and when it last triggered.

What file extension does a systemd timer unit use?

A .sched

B .service

C .timerunit

D .timer

Systemd timer units always use the .timer extension.

Which command starts a systemd timer immediately?

A systemctl start timer.timer

B systemctl start timer.service

C systemctl enable timer.timer

D systemctl run timer.timer

You start the timer unit with 'systemctl start timer.timer'.

What does the OnBootSec= option do in a timer file?

A Runs the task a set number of seconds after boot

B Runs the task at a fixed time daily

C Runs the task every second

D Disables the timer

OnBootSec= schedules the task to run after a delay from system boot.

If you want a task to run every 10 minutes, which timer setting is best?

A OnCalendar=hourly

B OnUnitActiveSec=10min

C OnCalendar=daily

D OnBootSec=10min

OnUnitActiveSec=10min triggers the task 10 minutes after the last run.

How do you check when a systemd timer last triggered?

A journalctl -u timer.timer

B systemctl status timer.service

C systemctl status timer.timer

D cat /var/log/timer.log

The status command on the timer unit shows last trigger time.

Explain how to create and enable a systemd timer to run a backup script every day at 2 AM.

Think about two files and scheduling with OnCalendar.

Describe how systemd timers differ from cron jobs and one advantage of using timers.

Focus on management and features differences.