update to 8.0-RELEASE --> partition gone

[Marcel Moolenaar]

On Dec 15, 2009, at 4:08 PM, Ben Morrow wrote:

> Quoth Marcel Moolenaar <xcllnt at mac.com>:
>> On Dec 15, 2009, at 2:20 PM, Steven Friedrich wrote:
>>>> 
>>> FreeBSD 8.0 no longer supports "dangerously dedicated" disks.
>> 
>> This is not true. The problem is that sysinstall creates an invalid
>> "dangerously dedicated" disk, as demonstrated by doing:
>> 	# fdisk ad8
>> 	(shows FreeBSD slice information)
>> 
>> 	# bsdlabel ad8
>> 	(shows valid but empty disk label)
>> 
>> Marian just needs to wipe out the second sector on the disk to
>> remove the BSD disklabel that prevents the kernel from using
>> the master boot record in the 1st sector. This exposes ad8s1.
>> This then will pick up the BSD disklabel in sector 65 (i.e.
>> the second sector in slice 1) to give ad8s1a...
> 
> Are you able to clarify exactly what is no longer working in 8?

Everything is working, but behaviour has changed for invalid
disks. Invalid disks are disks with conflicting partitioning
information. In FreeBSD 8.x the behaviour is deterministic
and for the broken dangerously dedicated disks that sysinstall
creates this means that we use the partition information in
the BSD disklabel. In FreeBSD 7.x this could come from either
the MBR or the BSD disklabel, with the MBR the more common
scenario.

> You seem
> to be implying here that there is only a problem if there are invalid
> and/or overlapping labels on the disk; elsewhere I have read that disks
> without an MBR aren't supported at all (I presume the faked-up MBR on a
> GPT disk counts).

Disks without an MBR are supported.

> If I currently have a working ad2{b,c,d,e}, will they
> be picked up by 8, or would I have to repartition slightly smaller with
> a useless MBR slice in front?

Yes, if you have ad2a and not ad2s1a, then you have a
proper dangerously dedicated disk and FreeBSD 8.x will
work correctly with your disk.

If you installed "dangerously dedicated" and ended up
with ad0s1a (note the "s1"), then you have an invalid
partitioning and FreeBSD 8.x will not give you what
you've been getting on FreeBSD 7.x. Most of the time
you only need to wipe out the second sector on the
disk to clean it up and have FreeBSD 8.x also give
you ad0s1a.

-- 
Marcel Moolenaar
xcllnt at mac.com