Cron & Task Scheduling (Cron/Systemd Timers/At)

Stop your scheduled tasks from stomping on each other

🧩 The Challenge

You ever have a script that takes ten minutes to run, but you scheduled it to go off every five? I’ve seen this wreck more production databases than I care to admit.

💡 The Fix

Use a file lock to ensure only one instance of your script ever runs at a time. It’s the easiest way to prevent a total resource implosion when things get backed up.

(flock -n /tmp/my_task.lock /path/to/script.sh) || exit 0

⚙️ Why It Works

The flock command checks for the existence of that file descriptor before letting the actual script launch. If it’s already held, the command just exits gracefully and leaves the existing process to finish its work.

🚀 Pro-Tip: Put this at the start of your crontab entry so you don’t even have to touch your actual script logic.

Linux Tips & Tricks | © ngelinux.com | 8/23/2026