Cron & Task Scheduling (Cron/Systemd Timers/At)
Stop cron jobs from overlapping like a traffic jam
🧩 The Challenge
You schedule a heavy backup script to run every hour, but then the database gets sluggish and the job takes longer than sixty minutes to finish. Suddenly you have five instances of the same script fighting for disk I/O and locking your tables into oblivion.
đź’ˇ The Fix
Use a simple lock file check at the start of your script to make sure only one instance runs at a time. It’s the most reliable way to prevent your server from eating itself alive.
if [ -f /tmp/myjob.lock ]; then exit 0; fi; touch /tmp/myjob.lock; your_backup_command_here; rm /tmp/myjob.lock⚙️ Why It Works
Checking for the existence of that lock file acts as a gatekeeper that kills the process immediately if a previous run is still hogging the resources. You’re effectively serializing the task without needing to touch complex scheduling configs.
🚀 Pro-Tip: Use trap to ensure the lock file gets deleted even if your script hits an error or gets killed by a signal.
Linux Tips & Tricks | © ngelinux.com | 11/6/2026