How to schedule a periodic task with systemd

Systemd uses different types of units. One of them is the timer unit, which can be used to schedule a periodic task. This timer unit is linked to an existing service unit and will activate the service according to the defined schedule. The timer unit can be defined using the information about systemd timers.

Timers use one or more OnCalendar definitions to specify when execution of the timer should happen. As systemd timers are very versatile and provide good monitoring options, they are a good replacement of cronjobs. The only downside is that slightly more configuration is needed when a just a single shell script needs to be executed, as you need to create both the timer as service unit.