Cron jobs allow you to schedule repetitive tasks on your VPS, such as backups, script execution, updates, and maintenance. This guide explains how to set up and manage cron jobs in Linux.
What is a Cron Job?
A cron job is a scheduled task defined in the system’s crontab (cron table). It runs automatically at specified intervals.
Step 1: Open the Crontab File
To edit the crontab for the current user:
crontab -eThe first time you run this, it may ask you to select an editor (choose nano if you’re unsure).
Step 2: Understand the Cron Format
Each line in the crontab has the following format:
* * * * * command-to-run
│ │ │ │ │
│ │ │ │ └──── Day of the week (0-7) (Sunday = 0 or 7)
│ │ │ └────── Month (1-12)
│ │ └──────── Day of the month (1-31)
│ └────────── Hour (0-23)
└──────────── Minute (0-59)
Step 3: Example Cron Job Entries
|
Task |
Cron Expression |
Example |
|---|---|---|
|
Run every minute |
* * * * * |
echo "Hello" >> /tmp/hello.log |
|
Run daily at midnight |
0 0 * * * |
/usr/bin/php /var/www/html/cron.php |
|
Run every Sunday at 2 AM |
0 2 * * 0 |
/root/weekly-backup.sh |
|
Run every 5 minutes |
*/5 * * * * |
curl -s http://localhost/healthcheck |
Step 4: View Current Cron Jobs
To list current cron jobs for the current user:
crontab -l
Step 5: Remove Cron Jobs
To remove all cron jobs for the current user:
crontab -rTo remove individual jobs, use crontab -e and delete the specific lines manually.
Step 6: Schedule a Cron Job for Another User (as root)
Edit another user’s crontab:
crontab -u username -e
Step 7: Redirect Output (Optional)
By default, cron sends output by email (if configured). To prevent this or log to a file:
• Suppress output:
* * * * * /path/to/command > /dev/null 2>&1
• Log output to a file:
* * * * * /path/to/script.sh >> /var/log/myscript.log 2>&1
Step 8: Confirm Cron is Running
Ensure the cron service is active:
• Debian/Ubuntu:
systemctl status cron
• CentOS/AlmaLinux:
systemctl status crond
If inactive, start it with:
systemctl start cron # Debian/Ubuntu
systemctl start crond # CentOS/RHEL
Conclusion
Cron jobs are a powerful way to automate system tasks and maintenance on your VPS. Use them wisely to save time and streamline operations.
For help setting up or troubleshooting cron jobs, contact Hosteons Support or access your server via https://vps.hosteons.com.
