Re: bootable disk: how?

[David Laight <david%l8s.co.uk@localhost>]

On Thu, Apr 17, 2008 at 05:45:11PM -0400, der Mouse wrote:
> 
> > Possibly something is confused in the CHS/LBA mapping, using mbr_ext
> > will force LBA disk reads.
> 
> Hmm.  Could this be related to the "can't determine number of heads"
> message?  (See the message referred to above.)

If fdisk is reporting that, then (I think) the disk isn't being reported
by the bios (in the list of known disks).  This can be confirmed using
'sysctl machdep.diskinfo' which should report the disks and their
corresponding bios disk number (0x8x) together with the size and
geometry reported by the bios.
If the disk isn't reported by the bios, then fdisk has to solve the
simultaenous equations from the mbr partition bounds to determine
the geometry used to set the mbr - which it assumes is the correct
bios geometry.

It might be that the bios is actually trying to boot a different disk!

        David

-- 
David Laight: david%l8s.co.uk@localhost