Linux hard lock? When?
The first thing to try if Linux locks up on you is to try switching to a different VC (virtual console) If you are in X, hit CTRL-ALT-F2, you can use F2-F6 . If you now see the login prompt , login as root and type this to kill X:
correction what I thinking :P After you do the killall X it will drop you back to the VC you logged in on.
This of course works best when you are booting runlevel 3 and not booting into X (runlevel 5) directly. I always recommend booting runlevel 3. It can save alot of headaches, if you are having problems with X.
If your system hangs while in console mode, try switching to a different VC. Login as root and type:
ps aux | grep login
This will show all the login shells running.
$ ps aux | grep login
root 1009 0.0 0.3 2336 776 tty1 S Jan13 0:00 login -- jimh
root 1010 0.0 0.4 2316 1092 tty2 S Jan13 0:00 login -- root
This shows jimh logged in on tty1 and root logged in on tty2. You can kill the shell by using the PID. The PID for jimh is 1009, and root 1010.
If the system is locked to the point you can't do anything then you will be stuck with hitting the reset button on the computer.