Cron jobs allow you to automate repetitive tasks on the server that hosts your web site. This is a powerful tool that allows you to take a hands-free approach to repetitive tasks. For example, you could add a cron job that automatically copies a mySQL database to a separate location on your site as a backup.
Warning: You need to have a good knowledge of Linux commands before you can use cron jobs effectively. Check your script with your hosting administrator before adding a cron job.
To add or modify a cron job:
Click on the Cron Jobs link in the Advanced Menu area.
Enter the times for the cron job in the Minute, Hour, Day, Month, or Weekday fields. Refer to the following page to check exactly how to enter values in these fields – http://www.redhat.com/support/resources/tips/cron/cron.html.
Enter the cron job script in the Command field.
Click on the button. Your cron job has now been added or updated.
Note: You can always click on the button to change the cron job back to whatever it was before you started entering information.