Schedule Cron wih Bash

Question

This is the command I want to run:

00 03 * * * backup.sh

I understand that this will run the script backup.sh at 3am every morning. How can I add this cron command on my linux server using a bash script?

Answer 1

As root:

echo "00 03 * * * root backup.sh" >>/etc/crontab

or

echo "00 03 * * * root backup.sh" >/etc/cron.d/mybackupjob

As your own user:

crontab -l >tmp; echo "00 03 * * * backup.sh" >>tmp; crontab tmp; rm tmp

Answer 2

crontab -e will attempt to invoke your EDITOR, so your first script could set this to a second script which just has to append the line in question to the crontab:

#!/bin/sh
EDITOR=/path/to/second/script crontab -e

Second script:

#!/bin/sh
echo "00 03 * * * /path/to/bin/backup.sh" >> $1

Answer 3

How can I add this cron command on my linux server using a bash script?

If you want to run this as root, you could place a file in /etc/cron.d named backup with the following contents:

00 03 * * * root backup.sh

This assumes that backup.sh is in the standard PATH, you probably want to use a fully qualified path here instead of relying on PATH:

00 03 * * * root /path/to/bin/backup.sh

On many distributions, you could also place (probably via a symlink) the backup.sh script into something like /etc/cron.daily and it would run every night. This is often simpler and more maintainable than writing your own crontab entries.

If you want to run this as a user, you can run...

crontab -e

...to edit your own crontab file and adding the entry there:

00 03 * * * /path/to/bin/backup.sh

Note that there we don't need to specify a user name (that's only necessary in /etc/cron.d, /etc/crontab, and other global system locations.

Answer 4

You know about the /etc/cron.d directory, right? If not, type 'man cron'.