Re: turning off COMPAT_386BSD_MBRPART in disklabel

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

On Thu, Feb 03, 2011 at 05:59:15AM -0500, Thor Lancelot Simon wrote:
> On Thu, Feb 03, 2011 at 08:01:34AM +0000, David Laight wrote:
> > 
> > The disklabel describes the partition layout of the disk (not the type
> > 169 mbr partition), it has to be saved on the disk.
> >
> > Saving it is ALL the partitions (and, IIRC, anywhere else it manages to find
> > a copy!) avoids confusion and allows the pbr boot code to find it.
> 
> But this is potentially very dangerous, in combination with
> COMPAT_386BSD_MBRPART, because FreeBSD considers labels to be per-"slice"
> (per fdisk-partition) and uses the 0x165 partition type.  So if we are not
> very careful, we can hopelessly wreck FreeBSD installations in other
> MBR partitions.

I'm not advocating (above) writing the NetBSD format label to a
type 165 mbr partition.
Quite clearly anything written to such a partition probably ought to
have relative sector numbers.

It might be an interesting exercise to detect a relative disklabel
in a type 169 partition - and convert it to absolute....
OTOH that isn't needed now.

        David

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