@reboot Cron Expression
Fires once when the cron daemon starts — typically at system boot.
Expression
@rebootTry it in the tester →Field Breakdown
@reboot
minute
@reboot
hour
@reboot
day-of-month
@reboot
month
@reboot
day-of-week
minutefires once at daemon startup
hourfires once at daemon startup
day-of-monthfires once at daemon startup
monthfires once at daemon startup
day-of-weekfires once at daemon startup
How It Works
`@reboot` is a Vixie-cron alias with no 5-field equivalent. It runs the job exactly once when crond starts — which is usually system boot, but also any time the daemon is restarted (config reload, package upgrade, etc.).
Example Run Times
- On boot
- On crond restart
- On package upgrade restart
- On `systemctl restart cron`
- On cron config reload
Frequently Asked Questions
Is `@reboot` portable?
It's supported by Vixie cron, cronie, and most Linux distributions, but not by strict POSIX cron, BSD cron, or Quartz. For boot-time work on systemd systems, prefer a unit with `[Install] WantedBy=multi-user.target`.
Does `@reboot` fire if I just restart the cron service?
Yes — most implementations treat any crond start as a 'reboot' for this purpose. That can lead to duplicate execution if you reload the daemon frequently.