December 13, 2024

Things That I Discovered

1. Prevent cronjobs from overlapping

• I recently started running Systemd timer for a recurring task; rclone sync, and wanted bare minimum time to re-run it, but here comes a caveat, if the execution doesn't finish in time, a new task might be started, resulting in overlap, and if the task is handling data, say database for an example. That can lead to data loss/corruption. We can use flock command to overcome this.

• Example:

  flock /var/lock/rclone-sync.lock -w 30 rclone sync <SOURCE> <DESTINATION>

• Here, flock command would check for a lock file at /var/lock/rclone-sync.lock and wait for 30 seconds before it exits with an error if a lock file is found.

• Read more at my TIL Website.

• Reference(s):

  • CleverUptime

  • Mattias Geniar Blog

  • Bashscript.net