Debugging kernel panics
Greg 'groggy' Lehey
grog at FreeBSD.org
Mon Sep 15 22:20:20 PDT 2003
On Tuesday, 9 September 2003 at 3:46:07 -0400, Michael Reynolds wrote:
> I've recently cvsup'd from 4.8-STABLE to 4.9-PRERELEASE. After a
> reboot, my machine's kernel panics at the initialization of the xl1
> device (a 3com nic). I've checked out the FAQ on the site, under
> advanced topics, regarding kernel panics, and read the relevant man
> pages. I have 2 swap partitions, ad0s1b, and ad2s1b. I have set
> dumpdev to "ad2s1b" in /etc/rc.conf and /boot/loader.conf. I've also
> built a debug kernel. However, it appears a kernel core is not being
> dumped on panic. I've manually executed savecore, with force option,
> and it wrote a 0 byte vmcore.
That probably means that there wasn't a dump there. You normally
don't need to force it.
> Is there anywhere else I need to specify the dump device?
No, that's all.
> Do I need to specify the full path instead of just the device?
Ah, yes, of course. There's no way for the dump routines to guess a
path. Try /dev/ad2s1b.
> I've not had a kernel panic before, so I'm pretty much a newbie when
> it comes to that aspect. I have no custom code added to the kernel.
> Any help will be *greatly* appreciated.
A couple of other points:
1. Your swap partition needs to be at least fractionally larger than
your real memory. The dump routines write a dump and a header.
2. You need enough space for the dump on /var/crash. Otherwise it
won't save the dump.
Greg
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