Sidebar: Using crontab to Start Backups Automatically

crontab is simple to use -- just be sure to specify the full paths of the commands in scripts to be invoked. For example, for crontab a script would invoke /bin/tar rather than tar. The $PATH environment variable is set differently when crontab starts a process.

To update crontab, enter crontab -e. In the resulting vi session, move to the bottom of the file and add a line such as the following:

30 22 * * * /bin2/autoback

Then, enter :wq to implement the update. This example starts the autoback script found in the /bin2 directory at 10:30 pm every day.

crontab checks for jobs once every minute. You can test its functioning as follows. Suppose the time is 9:45 and you are on tty23. Enter the command

46 9 * * * echo 'testing 1-2-3' >/dev/tty23

Then enter :wq before the date changes to 9:46. Watch for the message testing 1-2-3 to appear on your screen. Don't forget to delete the line after your test is finished! For more information try man crontab.