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minutehourday (month)monthday (week)

Common Examples

Cron Syntax

  • * — any value
  • , — list separator (1,3,5)
  • - — range (1-5)
  • / — step (*/15 = every 15)

Field Ranges

  • Minute — 0-59
  • Hour — 0-23
  • Day of Month — 1-31
  • Month — 1-12
  • Day of Week — 0-6 (Sun-Sat)

How to Set Up Cron on Linux

1. Open your crontab for editing:

crontab -e

2. Add your cron job (example: backup script every day at 2 AM):

0 2 * * * /home/user/backup.sh

3. Save and exit. View your cron jobs:

crontab -l

More examples:

Run a Python script every 15 minutes

*/15 * * * * /usr/bin/python3 /home/user/script.py

Clear temp files every Sunday at midnight

0 0 * * 0 rm -rf /tmp/*

Send a report email on weekdays at 9 AM

0 9 * * 1-5 /home/user/send_report.sh

Restart nginx on the 1st of every month

0 0 1 * * systemctl restart nginx

Log disk usage every hour

0 * * * * df -h >> /var/log/disk_usage.log

Database backup every day at 3:30 AM

30 3 * * * pg_dump mydb > /backups/db.sql

Check server health every 5 minutes

*/5 * * * * curl -s https://mysite.com/health

Renew SSL certificates on the 1st and 15th

0 0 1,15 * * certbot renew --quiet

Useful commands:

  • crontab -e — Edit your cron jobs
  • crontab -l — List your cron jobs
  • crontab -r — Remove all cron jobs
  • sudo crontab -u root -e — Edit root's crontab