This brief tutorial is going to show you how to use Crontab in Ubuntu to execute scheduled tasks. Crontab is a file in most Linux systems that holds scheduled tasks that are automatically run or executed at a given date and time. You can add as many tasks you want and when the date and time come, they will automatically be processed. So, if you want to schedule a task so that your computer automatically shutdown or restart at midnight, then this tutorial is going to show you how to do that in Ubuntu using the Crontab file.


  • Shutdown / Restart Ubuntu automatically using Crontab
  • Enjoy!

To get started, press Ctrl – Alt – T on your keyboard to open Terminal. When it opens, run the commands below to open Crontab file.

sudo gedit /etc/crontab




Next, add the line below at the end of the file and save. This line below will shutdown your computer at midnight everyday.

00  0   * * *    root   poweroff




Here are few things to remember about what we added in the file.

  • The time format is military or 24 hours format ( 0  — 23)
  • The * means all legal values.    (ex. if you want the task to run everyday of the week, put * in dow column)
  • If you want a task to run on multiple days of the week, then use this format in the dow column:  1,3,5 (Monday, Wednesday, Friday).
  • If you want a task to run on the 10th of every month, put 10 in the dom column.
  • If you want a task to run only in January, February and March, put 1,2,3 in the mon column.


min hour day/month month day/week user commands 00 0 * * * root poweroff

30 12 * * 5 root reboot


The first line above power down your computer everyday at midnight, of every week of every month.

The second line reboot your computer at 12:30 PM of everyday of the month or every month and only on Friday.


So you can add as many tasks are you want.