What are systemd timers and how do they compare to cron?

systemd timers are the modern cron alternative: a .timer unit defines when, a paired .service unit defines what — with proper logging and catch-up for missed runs.

The big conceptual difference from cron is the two-unit split: scheduling (.timer) is separated from the work (.service). That buys you integration with the rest of systemd — output goes to the journal (journalctl -u name), jobs can declare dependencies on other services, and Persistent=true reruns a job that was missed while the machine was off (cron just skips it). The cost is more boilerplate than a one-line crontab entry.

Advantages over cron:

• Better logging (journalctl)
• Can depend on other services
• More flexible time expressions
• Runs missed jobs after system boot

Components:

• .timer unit - defines schedule
• .service unit - defines what to run

Example timer unit:

# /etc/systemd/system/backup.timer
[Unit]
Description=Daily backup timer

[Timer]
OnCalendar=*-*-* 02:00:00    # Every day at 2 AM
Persistent=true               # Run if missed

[Install]
WantedBy=timers.target

OnCalendar examples:

Manage timers:

systemctl daemon-reload
systemctl enable --now backup.timer
systemctl list-timers