On Feb 3, Perry E. Metzger wrote
> 
> Jukka Marin writes:
> > What do I do when it freezes?  :-)
> 
> hit ctrl-alt-esc, I believe. That will put you at the ddb prompt. At
> that point, you can explore what is running, force a kernel core dump
> (which might be useful for someone to remotely analyse), etc.

Some more infos about this:
once you have th 'db>' promt (after ctrl-alt-esc), you have the following
commands:
'tr' will show the function calls trace (also called 'stack trace')
'ps' will list the processes with their status.
'call cpu_reboot(0x104)' will reboot the machine whithout syncing the disks,
   and creating a core dump (the flags are in /usr/include/sys/reboot.h).
You also have a 'help' command.
To understand what happens here, we need the stack trace. If you know of a
process which is hung (for example you typed 'ls' and it keeps blocked)
then 'ps' will says you on what resource it's wainting. And if you can get 
a core dump, someone else (or you) can then examine it and find in which state
the kernel was.

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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