cron job every day to reboot at 04:00?

Issue command

sudo crontab -e

Then modify

0 4 * * *  /sbin/init 6

Save and exit

There are also some tools available:

http://kshutdown.sourceforge.net/

http://manpages.ubuntu.com/manpages/maverick/man1/qshutdown.1.html

https://launchpad.net/complexshutdown

etc.

wmp

... or this:

http://www.liberiangeek.net/2010/09/schedule-shutdownrestart-tasks-ubuntu-10-10-maverick-meerkat/

i've tested both suggestions separately and they don't work....

0 4 * * *  /sbin/init 6

&

0 4 * * * shutdown -r now

Note to test I reset time using date -s 03:59, but the linux pc did not reboot when it reached 04:00

After resetting the time you'll have to restart the cron daemon, afaik, to make the new time known to ut.

wmp

Make sure the cron daemon is running.  If it is up and running, it should read the time without restarting.

check:
ps -ef | grep cron

Also check the /var/spool/cron*/* directory:

cat /var/spool/cron*/*

You'll need to set a user to run as, and a full path to the shutdown command, so:

0 4 * * * root /sbin/shutdown -r now

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You can make it run as root if you are either:

issue this command as root
crontab -e

Or
sudo crontab -e -u root

That would make the above commands work.

i have followed the following procedure using the commands:

1. opened crontab as root
fcrontab -e

2. entered reboot command which allow reboot at 04:00 every day.
0 4 * * * shutdown -r now

( and also 0 4 * * *  /sbin/init 6)

3. set date to 03:59 to test reboot
date -s 03:59

4. restarted crontab
/etc/init.d/cron restart

However the linux ubuntu pc still does not reboot at 04:00

xterm it seems to work @ 4pm thanks when i checked the log file!

Nov  8 04:00:00 ubuntu fcron[1969]: SIGTERM signal received