Linux – how can I schedule a reboot in Linux

You must reboot after a kernel update (unless you are using KSplice), anything else is optional. Personally I reboot on a monthly cycle during a maintenance window to make sure the server and all services come back as expected. This way I can be reasonably certain if I have to do an out of schedule reboot (i.e. critical kernel update) that the system will come back up properly. Automated monitoring of servers and services (i.e. Nagios) also goes a long way to helping this process (reboot, watch the lights go red and then hopefully all back to green).

P.S. if you do reboot regularily you'll want to make sure you tune your fsck checks (i.e. maximal mount count between checks appropriately, otherwise a quick 2 minute reboot might take 30 minutes if the server starts fsck'ing a couple terabytes of data. I typically set my mount count to 0 (tune2fs -c 0) and the interval between checks to 6 months or so and then manually force an fsck every once in a while and reset the count.

If it is one-time deal, you can use shutdown command with -r as argument. Instead of using shutdown now, you can add time as parameter (e.g. shutdown -r 12:30).