My Linux server (Redhat 6.2) hangs and I can't access it through SSH or anything. What can I do to reboot it ?

Contact the data center and ask for a manual reboot. They are the only ones who can really help when you can get access to it.

If nothing is responsive on it, you're pretty much out of luck. If you know how to and you have a static ip to allow access to, you may want to setup telnet on a non-standard port and only allow your ip access to it incase something does occur and ssh goes down or is inaccessible in the future.

Thats a good point but what if something is wrong with the box for example a full partition preventing anything from running. I do like the telnet on a different port suggestion.

Thanks. I do have access to it. How do I do a manual reboot ?

If you are in Redhat and somehow logged in through telnet or have access to a prompt, just "shutdown -r now" and cross your fingers.

That's the problem - I don't have access to any prompt right now as we mostly do our work via SSH. I tried attaching a keyboard directly to the server - should I be able to reboot it that way ?

If you're at the computer and you've got a keyboard attatched, turn a monitor on, or if you're confident that you can do it without a monitor, just type root, enter, password, enter, shutdown -r now, enter.

If you're actually at the computer you can easily hard boot it, or you can play it safe and use the shutdown or reboot command.

Thanks, guys. Had to do a manual reboot (I did cross my fingers :)) - and everything is back up now... Phew!