More than 8 labels per slice

Robert Watson rwatson at
Tue Apr 27 17:36:57 PDT 2004

On Tue, 27 Apr 2004, Harald Schmalzbauer wrote:

> is there any chance that FreeBSD can adopt the OpenBSD changes reagrding
> UFS labels? I'm using one label per jail and this old 8 label limit
> forces me to use different slices which sometimes, when I have to change
> label sizes, is a big handicap.  Having 16 labels would improove the
> jail-handling greatly IMHO. Having 32 labels (like I think NetBSD) was
> even greater, but lifting the 8 label limit would suffice I think. 

I can't speak specifically to the OpenBSD changes, but in FreeBSD 5.x, you
can nest disk labels inside other disk labels:

paprika# mdconfig -a -t swap -s 16m
prika# disklabel -w md0 auto
paprika# ls /dev/md0*
/dev/md0        /dev/md0a       /dev/md0c
paprika# disklabel -w md0a auto
paprika# ls /dev/md0*
/dev/md0        /dev/md0a       /dev/md0aa      /dev/md0ac      /dev/md0c

So you can sub-divide slices and partitions into other slices and
partitions.  At 8 subdivisions per layer, that adds up fairly quickly,
although it's a little less convenient to lay out.  In 5.x, we also
support the GPT format, which supports up to 64k partitions per disk, but
I'm not sure that code is enabled on i386 by default, only ia64.  If not,
we probably should enable it there.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at      Senior Research Scientist, McAfee Research

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