disklabel differences FreeBSD, DragonFly

[Dmitry Marakasov]

* David Gilbert (dgilbert at dclg.ca) wrote:
> Dmitry> About `lack' of partitions - don't forget that labels can be
> Dmitry> nested.  Just do `bsdlabel -w /dev/ad0s1e` - you'll get
> Dmitry> /dev/ad0s1ea.
> Don't also forget that gpt(8) exists and seems to provide for large
> numbers of partitions.  It even seems to be compiled into GENERIC by
> default.
Afaik, one is unable to boot from gpt partitions. However, I myself
didn't try it yet. Do gpt fully eliminate need in mbr/bsdlabel
partitioning? There is also issue with UFS filesystems and bsdlabel
- some filesystem data is stored in label itself:

# bsdlabel /dev/ad0s1
#        size   offset    fstype   [fsize bsize bps/cpg]
  a:   262144        0    4.2BSD     2048 16384 16392 
                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For example, fsck(8) makes use of it - you can

newfs /dev/ad0s1a && fsck /dev/ad0s1a

but you can't

newfs /dev/ad0 && fsck /dev/ad0

the latter will complain about unknown filesystem type and you'll
have to use fsck_ufs instead. This shouldn't affect automatic fsck
(because of fstab), but I can't guarantee that there are no any
other drawbacks.

-- 
Best regards,
 Dmitry                          mailto:amdmi3 at mail.ru