I have tried solutions on a half dozen sites like stack exchange and none of them work.

I tried adding a rule under /etc/crontab, using sudo crontab -e, and placing a file in /etc/cron.d. No luck.

Distro is SUSE 13.2.
Desktop is KDE.

I want to add a cron job in a file under /etc/cron.d. I do not wish to use crontab -e, as I can't even undertand how it works (or why it's not working in this case) and I'd rather just be able to open a file in a GRAPHICAL editor under /etc/cron.d

I want this job to absolutely force REBOOT with a 5 minute notification. I want the reboot to be forced, absolutely nothing stopping it.

I tried it several times without effect.

Last attempt tried to set for 5:17 pm, restarted cron, then waited, and nothing happened.

0 5 17 1/1 * ? * /sbin/reboot

Update: last attempt I created a file zz-reboot in /etc/cron.d and added:

03 18 * * * /sbin/reboot

I waited a few minutes for the clock to catch up and nothing happened.

Thank you kindly.

0 5 17 - it will run 5 AM on 17th.

http://www.dataphyx.com/cronsandbox/cronsandboxgui.php

Good stuff, Maynard!

The sandbox is a nice idea. I used cronmaker for one command that did not work, then went key one in manually. Still no workie.

03 18 * * * should fire the cron job at 18:03 daily, should it not?

I have repeatedly set the time for the cron a couple minutes ahead of the clock and waited for the clock to catch up. The cron will not execute. I have no idea why.

I discovered the problem.

The cron system requires a newline at the end of EVERY line in the crontab file.

This means that when editing a crontab, one must press ENTER at the end of the command. Cron will not process a file missing this required newline.