Re: [gentoo-user] Kernel crash - howto find out what happened?

[Alexander Puchmayr <alexander.puchmayr@linznet.at>]

On Dienstag, 14. Oktober 2008, Daniel da Veiga wrote:
> On Sun, Oct 12, 2008 at 07:08, Alexander Puchmayr
>
> <alexander.puchmayr@linznet.at> wrote:
> > Hi there!
> >
> > MY gentoo system (an amd64@4400+, 2GB ram, nforce4-chipset) worked fine
> > for nearly two years, but now it frequently freezes, sometimes (not
> > always) scrollock and capslock LED blinking).
> >
> > Since I'm using the box as desktop, I have only a frozen X-server and
> > no possibility to switch to console (maybe there's some hint whats
> > happened?).
> >
> > How do I find out what happened, why it crashed? Modern systems have
> > MCE-logs, but how do I read it in this case? After reboot, all
> > information seems to be gone since mcelog is always empty.
> >
> > I assume there's some problem with some hardware, I already tested RAM
> > with memtest86, but no errors.
>
> I had one of this freezes today.
> Simply killed X using CTRL+SYSREQ+K and got back a console with error
> messages.
>
> Have you tried the SYSREQ keys?

How does this work? I've tried it but I didn't get this working at all. 
AFAIK, first step is to compile the CONFIG_MAGIC_SYSRQ into the kernel. 
Then, make sure there's a "1" in /proc/sys/kernel/sysrq; well it is.
/usr/src/linux/Documentation/sysrq.txt says press "ALT-SysRq-<command key>", 
I've tried it out with SysRq=printScreen and cmd='h' for help, but nothing 
happens, even under normal conditions. What did I make wrong? 

Alex