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

Ivan Voras ivoras at
Mon Apr 23 19:42:56 UTC 2007

Tom Cumming wrote:
> All of the doc's I can find are for getting a kernel dump after it's booted
> (i.e., set the dumpdev using dumpon, etc.). I have a panic during boot and
> it says it won't dump b/c there's no dump device. I cannot find any doc's
> anywhere that mention how to set the dump device before you boot (i.e.,
> from
> the loader, patch the kernel, whatever...). Does anyone know how to get an
> early dump?

Can you boot from a Live CD ("Fixit CD", CD1 in the set), and either
configure it from there, or build a kernel with debugging installed so
it presents you the debugger when it panics?

If you have a "snapshot" CD of 7-current, its kernel is already
configured with KDB, so if it panics, you can get a backtrace and
transcribe it.

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