Gmirror dump device does not exist?

Michal Mertl mime at
Fri Jan 6 01:41:09 PST 2006

Nick Pavlica wrote:
> All,
>   I have just set up a FBSD6.0 server configured with gmirror/raid1
> using two SATA drives ad4 & ad6 according to these instructions:
>   Everything is functioning properly with the exception of a boot
> warning that indicates that a dump device does not exist.  I'm sure
> that I just missed something simple during the setup procedure.  Does
> anyone have the quick fix for this?

It is not possible to dump kernel to gmirror.

The reason is that at the time, when the kernel is dumping core, it is
usually in pretty bad state, kernel internals may be corrupted and so
on. The dumping code is therefore written to be quite low level so that
even wedged kernel can be dumped. The dumping code is part of hard disk
controller's drivers. The gmirror is quite high-level device and geom
itself needs working scheduler so there will probably never be a way to
dump on gmirror provided swap. When the dumpon command is issued the
check is performed whether the driver for the disk you want to dump on
supports kernel core dumps.


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