You Don't Love Systemd Timers Enough
6 hours ago
- #systemd
- #cron
- #timers
- The term 'cron job' is a metonym for scheduled tasks, even if not literally executed by cron daemons.
- systemd timers are recommended over traditional cron for scheduled tasks due to modern features and better reliability.
- Cron has issues like ambiguous PATH settings, lost stdout/stderr output, and difficult execution history tracking.
- systemd timers solve cron problems and offer clearer scheduling, easier management, and better integration.
- Creating a systemd timer involves defining a .service unit (the task) and a .timer unit (the schedule).
- Timer schedules can be calendar-based (e.g., daily at 10:00) or relative to events (e.g., after boot).
- The systemd-analyze calendar command helps validate and explain time expressions.
- systemctl list-timers provides a comprehensive overview of all active timers on a system.
- Timer options like WakeSystem= can resume a suspended system to run tasks, and Persistent= handles missed activations.
- RandomizedOffsetSec= and FixedRandomDelay= help prevent thundering herd problems by spreading out execution times.