disklabel differences FreeBSD, DragonFly

Andreas Klemm andreas at freebsd.org
Sat Jul 29 09:50:09 UTC 2006

On Fri, Jul 28, 2006 at 03:36:27PM -0700, Matthew Dillon wrote:
> :On Thu, Jul 27, 2006 at 02:21:59PM +0200, Joerg Sonnenberger wrote:
> :> On Thu, Jul 27, 2006 at 08:39:37AM +0200, Andreas Klemm wrote:
> :
> :Hmm, for the sake of compatibility, wouldn't it have been an option,
> :to add this extra bit to the end of the struct ?
> :	Andreas ///
>     The thing to note here is that FreeBSD had to make room for the
>     UFS1+UFS2 boot code, so it moved the boot code back to the point
>     where it abuts the 8-partition-sized disklabel.
>     So at least insofar as FreeBSD goes, the partition table cannot be
>     expanded to 16 partitions with UFS1+UFS2 boot code.  I'm guessing
>     that it *could* be expanded to 16 partitions with UFS1 only or 
>     UFS2 only boot code (assuming the boot code were relocated back
>     to where it was originally in FreeBSD-4/5 times, before UFS2 came
>     along).
>     With regards to simply recognizing a DragonFly partition... yes,
>     that would be easy to do.  Since FreeBSD is now devfs-based, the
>     bit we had to steal to support 16 partitions in /dev isn't an issue.

Couldn't all BSDs restructure the disklabel in -current so that
we would have the same base for the next major release ?

Then its only a question of drivers to suppot UFS2 or not.

But then compatibility would be there for some time ...

Incompatible to UFS's like from Sun I think we are already, so we
don't have to honour them. Remember a current thread in german BSD
group where somebody complained about FreeBSD - mounting a Sun
filesystem r/w - destroyed the filesystem. Luckily he could recover
using fsck -b 32.

	Andreas ///

Andreas Klemm - Powered by FreeBSD 6
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