> > I've tried running 'installboot /dev/sd0a /usr/mdec/bootxx /boot' as
> > described in the installboot manpage (yes, /dev/sd0a is my root file system)
> > but this complains that the device is busy (same result in single user
> > mode).
> 
> Isn't that meant to be:
> 
>   installboot /dev/rsd0c /usr/mdec/bootxx /boot
> 
> (partition c)?
> 

No. The boot program goes on a partition (yes, you can have multiple
boot programs, if you like), not on a "disk".

But you should use the raw device, i.e. /dev/rsd0a in this case.

-pk