Panic on boot. How do I get a kernel dump.

Eric Anderson anderson at
Fri Apr 27 01:30:36 UTC 2007

On 04/26/07 20:24, Wilkinson, Alex wrote:
>     0n Thu, Apr 26, 2007 at 03:35:15PM -0700, Tom Cumming wrote: 
>     >>What about using the "panic" command in ddb? :)
>     >
>     >
>     >The problem is not getting it to panic, the problem is getting it to save
>     >core after the panic. I can find no way to configure the dump device before
>     >I boot, only after the OS is up. This means a panic during boot will not
>     >dump core because the dump device is not configured.
> Boot off of a good kernel and:
>    # boot -s
>    # fsck -p
>    # mount /var
>    # savecore /kernel.broken /var/crash

Does this make any sense?

I think what Tom was trying to say was that while the kernel is booting, 
say right at root mount time, there is no dump device set, so the kernel 
doesn't know where to dump the dump when a 'call doadump' is initiated.

I think what he (and others) want to know is: how to set the dump device 
at the loader prompt so you can get a crash dump before the dump device 
normally would get set up in /etc/rc.d/dumpon


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