reboot after panic

[Clifton Royston]

On Tue, May 06, 2008 at 06:56:42AM -0700, Jeremy Chadwick wrote:
> On Tue, May 06, 2008 at 09:47:59AM -0400, Stephen Clark wrote:
...
> > but there is never one. It is like it hangs trying to dump the memory image.
> >
> > This mother board has both sata and pata controllers but I am using only pata
> > drives.
> 
> A kernel panic causes the kernel to dump all memory contents (from start
> to end) to whatever swap device is available.  It's written to the disk
> in a fairly "raw" format, with some header data of some sort I think.
> After it's done, the system should reboot.
> 
> My guess is that you either don't have any swap defined, swap is defined
> incorrectly (disklabel -r output would be useful), or your swap space is
> smaller than your total amount of memory.  (Swap should usually be 2x
> RAM).
> 
> dumpdir and dumpdev are used during the startup process, where
> savecore(8) is called.  The memory dump on the swap device is extracted
> and stored in a file in $dumpdir, which you can examine later.  Keep in
> mind that savecore(8) will use /dev/dumpdev, which is a symlink to
> whatever device your swap lives on -- and that's determined by reading
> /etc/fstab.
> 
> Does this help?  :-)

  You might consider the possibility that he is correct in what he has
said, rather precisely, is going on.  FreeBSD 6.2 (and apparently 6.1)
can indeed double-fault or hang during the panic dump in which case no
reboot occurs and there is nothing successfully dumped to analyze for
debugging, either.  It is likely that it only occurs with certain
hardware conditions or configurations, which is why not everyone would
see it, but that's not the same thing as it being a hardware problem.

  I've been seeing this on all of my SMP machines since October, and
have reported it onlist, and I've been successfully running FreeBSD for
nearly 10 years (starting with 3.3) and BSD/OS for years before that. 
It ain't necessarily PEBKAC.

  -- Clifton

-- 
    Clifton Royston  --  cliftonr at iandicomputing.com / cliftonr at lava.net
       President  - I and I Computing * http://www.iandicomputing.com/
 Custom programming, network design, systems and network consulting services