Cron & Task Scheduling (Cron/Systemd Timers/At)
Stop cron from running overlapping jobs when tasks hang
🧩 The Challenge
Every once in a while, a database backup or a cleanup script gets stuck, and then the next cron job starts up right on top of it. Before you know it, you’ve got ten processes fighting for the same lock and your server load is through the roof.
đź’ˇ The Fix
Use a lock file check to see if the script is still running before you let it start again. It saves your CPU from turning into a space heater during peak hours.
flock -n /tmp/my-job.lock -c "/usr/local/bin/my-script.sh"⚙️ Why It Works
The flock utility attempts to acquire an exclusive lock on that file, and if it can’t, it just exits immediately without running your script. It is the cleanest way to prevent race conditions without needing to write messy PID file checks in every single bash script.
🚀 Pro-Tip: Stick this directly in your crontab entry so you don’t have to rewrite the logic inside your actual scripts.
Linux Tips & Tricks | © ngelinux.com | 8/18/2026