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Date:      Wed, 25 Jun 2008 17:11:56 +0300
From:      Toomas Aas <toomas.aas@raad.tartu.ee>
To:        questions@freebsd.org
Subject:   Cannot get kernel core dump
Message-ID:  <200806251711.56906.toomas.aas@raad.tartu.ee>

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Hello!

I'm trying to report a problem which involves kernel panic, but I cannot get a 
core dump. The system is 7.0-STABLE from June 18th.

I've set the following in /etc/rc.conf (and of course rebooted, even several 
times):
dumpdev="/dev/ad0s1b"
dumpdir="/home/crash"

The machine has 512 MB RAM and swap partition is also 512 MB, but according to 
dumpon(8) this shouldn't be a problem, because hw.physmem is still somewhat 
smaller than the swap partition:

bsd# sysctl hw.physmem
hw.physmem: 527863808

bsd# swapinfo
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b        524288        0   524288     0%

/home partition, where I've created the crash directory, has 55 GB free space.

When the machine boots up, it dutifully reports:
kernel dumps on /dev/ad0s1b

Then I "do the thing" that causes the panic. System prints the panic message 
and hangs. Only thing left to do is press the reset button. On next boot, the 
log says
savecore: no dumps found

When the system panics and prints the panic message, it doesn't say anything 
about saving the coredump. I haven't had a kernel panic for a long time, but 
I seem to remember that in the past there was some kind of message to that 
effect.

Are there known conditions under which the core dump really isn't recorded, or 
am I simply missing something obvious?

--
Toomas



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