Ubuntu – Command with percent symbols not running in crontab

I have three solution suggestions for you.

1. Invoke the crontab with crontab -e -u root

2. Make sure that you have an empty line at the end of the cronjob file, meaning that every line ends with a newline.

3. You might need to redirect the output to devnull: shutdown -r now > /dev/null

Here are two helpful webpages for cronjobs:

CRON Tester

CRON Generator

You can also handle the cronjobs neatly with webmin.

Other than that, you have at least two more ways for restarting your computer at midnight.

One is to run the shutdown command as a script automatically at login but with specific time as a parameter instead of "now":

shutdown -r 00:00

However, this will yield a broadcast message of upcoming shutdown at every login (might not be a bad thing at all). Well you can also make this be run at boot time by adding the script in init.d, still yielding the message, though.

Another is to use atcommand:

at 0am

Enter command shutdown -r now and save it with ctrl+d or do a script for the command and do:

at -f restart_script.sh 0am

Hope these help you to get the result you wanted.

A few notes here before this would work:

1. Don't use sudo in a cron job. Instead edit root's crontab instead of your own, e.g. sudo crontab -e and then enter commands without sudo.
2. As @mikewhatever mentioned, this is an odd use for cron, and would likely be better placed in /etc/rc.local before the exit 0 line.
3. If you tell us exactly what you're looking for, we might be able to direct you to a log or config option (restarting your network services at startup feels a little hackish).
4. On most systems @reboot should also run after a hard shutdown or crash, but there are different cron implementations so YMMV. I've seen comments in different places asserting both.

EDIT (2016/02/17): Removed incorrect blurb on absolute paths; kudos @muru
EDIT (2016/10/17): Added shutdown note
EDIT (2017/09/11): Revised shutdown note. Not really sure on that one.