problems obtaining kernel dump

[Fabian Keil]

Roman Bogorodskiy <novel at FreeBSD.org> wrote:

> I'm having a problem obtaining kernel dump. The box has 512Mb of RAM.
> 
> In rc.conf I have:
> 
> dumpdev="/dev/ad4s1b"
> dumpdir="/var/crash"
> 
> swapinfo -h gives the following:
> 
> Device          1K-blocks     Used    Avail Capacity
> /dev/ad4s1b       1048576       0B     1.0G     0%
> 
> /var/crash directory exists, and the root partition where it is placed
> has enough space as well:
> 
> /dev/ad4s1a    989M    350M    560M    38%    /
> 
> The box runs fresh FreeBSD/i386 -CURRENT.
> 
> So, I do swapoff and then perform actions to reproduce the crash and it 
> breaks me into ddb prompt.
> 
> I do:
> 
> call doadump
> continue
> 
> it reboots, and when I run "savecore -v /var/crash /dev/ad4s1b" it
> prints:
> 
> unable to open bounds file, using 0
> checking for kernel dump on device /dev/ad4s1b
> mediasize = 1073741824
> sectorsize = 512
> magic mismatch on last dump header on /dev/ad4s1b
> savecore: no dumps found
> 
> The same happens when I do 'panic' instead of 'call doadump' like
> handbook suggests. What am I doing wrong? I googled for similar
> problems, found some mail threads but didn't find meaningful advises
> though.

I'm seeing a similar problem with an amd64 system on a SATA disk
running CURRENT from 20080727 (can't update as I'm using Pawel's
ZFS patch and upgraded most of the zpools).

Calling panic leads to an instant reboot,
nothing seems to be dumped.

Fabian
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