Scheduling Tasks: Cron vs Systemd Timers

For decades, crontab -e was the only way to schedule jobs. Now, Systemd Timers provide a modern alternative.

The Cron Way

# Run backup at 3 AM daily
0 3 * * * /usr/bin/backup.sh

Pros: Simple, one-line setup. Universal. Cons:

• If job fails, where do logs go? (Usually emailed to dead root mailbox).
• If computer is off at 3 AM, job is skipped completely.
• Hard to manage dependencies.

The Systemd Timer Way

Requires two files: a Service (what to do) and a Timer (when to do it).

backup.timer:

[Timer]
OnCalendar=*-*-* 03:00:00
Persistent=true  # Catch up if missed!

[Install]
WantedBy=timers.target

Pros:

• Logging: Output goes to journalctl.
• Persistence: If off at 3 AM, it runs immediately on boot.
• Accuracy: monotonic timers, randomization (prevent thundering herd).
• Dependencies: "Don't run Backup unless Network is Online".

Verdict

For simple user scripts? Cron is fine. For critical system infrastructure, backups, and production apps? Systemd Timers are superior.