[TriLUG] How would you diagnose "random" system hangs?

[James Olin Oden]

On 5/6/07, Andrew Perrin <clists at perrin.socsci.unc.edu> wrote:
> My home system has been freezing up at apparently random times -- usually
> when I'm at work, so I come home to a frozen machine that has to be
> cold-booted. How would you go about checking this out? I've let memtest86
> run continuously for 24 hours with no errors, so I don't think it's
> memory. I have the sensors reporting hourly to a log, and there are no
> temperature concerns (generally between 37 and 40C). There's nothing of
> interest in syslog that rings any bells to me. Any ideas?
>
> The machine is an ASUS A8N-E, nForce chipset, with an Athlon64 dual-core
> CPU and 4GB of RAM in it. It's running debian etch, but with a
> home-compiled kernel 2.6.20.7.

You might trying using magic-sysrq sequence to get something from the kernel:

   http://snafu.freedom.org/linux2.2/docs/sysrq.txt

If you can't get anything from that you at least know that its a hard
freeze.  Now a hard freeze can be in the kernel, but typically its in
the hardware.  Even things like the timing on the front side bus
getting hosed can cause this.  Looking at the sensors is a good thing,
but it may not tell you what you want.  Unfortunately, at the point
that you know its a hard freeze, various hardware monitoring tools
that hook into a jtag port become or the processor fits over become
more usefull.

If it really is in the kernel, then trying different distros with
different kernels can verify this (or at least point in this
direction).  Is it a 2.6 kernel thing?  If it doesn't happen on 2.4
but it does on 2.6, then its likely it is.  If you knew that much you
could then start trying different 2.6 kernels.

In the end, a hard hang can be very difficult to figure out.

Good luck...james
>
> ----------------------------------------------------------------------
> Andrew J Perrin - andrew_perrin (at) unc.edu - http://perrin.socsci.unc.edu
> Assistant Professor of Sociology; Book Review Editor, _Social Forces_
> University of North Carolina - CB#3210, Chapel Hill, NC 27599-3210 USA
> New Book: http://www.press.uchicago.edu/cgi-bin/hfs.cgi/00/178592.ctl
>
>
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