How to do a kernel dump?

[Denny White]

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Today Olivier Nicole spake forth boldly:
> Hi,
>
> I'd like to get a kernel dump when the machine panics.
>
> I set-up dumpdev="/dev/rda0s1b" in /etc/rc.conf.
>
> My swap is:
>
> amanda<on>41: swapinfo
> Device          1K-blocks     Used    Avail Capacity  Type
> /dev/rda0s1b      1048448        0  1048448     0%    Interleaved
>
> My memory is only 256 MB, so the swap is large enough to keep up to 4
> dumps. But still no dump, no image created in /var/crash, the system
> reboots in multi-user mode and period.
>
> When I try savecore by hand I get:
>
> savecore: reboot after panic: page fault
> savecore: system went down at Thu Mar  2 01:13:26 2006
> savecore: no dump, not enough free space on device (235544 available,
> need 264924)
>
> How should I understand that? Is it because I use the raw device (that
> is not clear in the handbook).
>
> System is:
>
> FreeBSD amanda.cs.ait.ac.th 4.11-RELEASE-p14 FreeBSD
> 4.11-RELEASE-p14 #5: Tue Feb 28 16:07:07 ICT 2006
> root at amanda.cs.ait.ac.th:/usr/obj/usr/src/sys/SMALL  i386
>
> Thanks in advance,
>
> Olivier
> _______________________________________________
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>

This isn't guaranteed 100% correct, but at least if it's not,
maybe it'll get someone else involved.
Below my "dumpdev" in rc.conf I have
savecore_flags="-z"
to compress the core dump & kernel with gzip. Also, read man savecore
again, esp the part about minfree in /var/crash & free kilobytes for
non-superusers in the file system after the copies would be made.
Hope this helps.
Denny White

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