Recovering from a hard X lock up

[Tim]

On Mon, 2009-08-10 at 10:39 +0100, James Allsopp wrote:
> My Fedora 10 machine locks up X completely, but I can still login via
> SSH. The monitor still shows the X window, but nothing changes, no
> clock, mouse nothing. X processes are still running, but not sure how to
> go about shutting them down. Last night, I tried to get the system to
> shut down sanely by running shutdown -h now and although the command ran
> and I couldn't login via ssh anymore, the machine did not shut down.
> 
> Can anyone tell me how to shutdown and restart X properly. Tried things
> like startx( had a x lock file exists error) and init 3, but nothing worked.

If X hadn't completely locked up, CTRL+ALT+BACKSPACE would have
restarted X (that is BACKSPACE, the delete key that deletes to the left,
not the DEL key that deletes to the right).

If the keyboard was still being listened to, then CTRL+ALT+DEL should
have rebooted (perhaps after hammering away at the keys a lot), as a
second option instead of CTRL+ALT+BACKSPACE.

If the keyboard was still being listened to, and you'd enabled the magic
keys (darn, I've forgotten the proper terms for making use of the SYS
REQ keys), you would have had more options about wresting control back.
But that requires you to know what you're doing.

However, it sounds like you've almost got the machine to shutdown, but
not quite, and left yourself in a state with way to control it any more.
You could try CTRL+ALT+DEL, or maybe CTRL+ALT+F2 to see if you can get
to a local console, then CTRL+ALT+DEL, repeatedly until something quits
and lets it continue to shutdown.

But you might well be stuck with having to just turn off the power.  Are
you avoiding that out of cautiousness, or are you hoping to recover
something that might get trashed if you pull the power?  

I've found Linux to be quite resilient to not destroying itself if the
power is rudely switched off.  Heck, way back with Fedora Core 4, we
once tried turning the power off repeatedly, at inopportune moments, to
see if we could give it problems.  No problems were detected.

I've found one or two machines that will occasionally start to shutdown,
then just sit there stuck part way through the process.  Holding down
CTRL+ALT and repeatedly hitting DEL usually whips them into shape,
forcing some stubborn thing to quit, so the computer can continue
shutting down.  It's always something that happens just as I want to nip
out, so I don't have the time to diagnose which part of the shutdown
process has got stuck.

-- 
[tim at localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

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