How to setup Cron Jobs in Ubuntu [STEP BY STEP]

If you want to run a task on regular basis the Cron Service will help you.

How to setup Cron :

Put a shell script in one of these folders: /etc/cron.daily, /etc/cron.hourly, /etc/cron.monthly or /etc/cron.weekly.

If these are not enough for you, you can add more specific tasks e.g. twice a month or every 5 minutes. Go to the terminal and type:

crontab -e

This will open your personal crontab (cron configuration file). The first line in that file explains it all! In every line you can define one command to run and its schedule, and the format is quite simple when you get the hang of it. The structure is:

minute hour day-of-month month day-of-week command

For all the numbers you can use lists, e.g. 5,34,55 in the minutes field will mean run at 5 past, 34 past, and 55 past whatever hour is defined.

You can also use intervals. They are defined like this: */20. This example means every 20th, so in the minutes column it is equivalent to 0,20,40.

So to run a command every Monday at 5:30 in the afternoon:

30 17 * * 1 /path/to/command

or every 15 minutes

*/15 * * * * /path/to/command

Note that the day-of-week goes from 0-6 where 0 is Sunday.