A systemd timer is a unit file (extension .timer) that triggers another unit — usually a .service with the same base name — on a schedule. Unlike cron, timers are logged in the journal, support monotonic schedules relative to boot, can wait for other units, and integrate with systemd's dependency graph. On RHEL 10, every .timer comes in a pair with a matching .service: logrotate.timer triggers logrotate.service, and so on. The timer is what you enable; the service is what gets run.
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