gpart and bsdlabel

[Rolf Nielsen]

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On 2014-07-11 22:11, Michael W. Lucas wrote:
> Hi,
> 
> I'm gradually switching from the familiar and comfortable agony of 
> fdisk/disklabel to gpart.
> 
> In the past, our org has avoided certain partition letters on
> specific drives. If the drive isn't a boot drive, it has no 'a"
> partition. If it has no swap, it has no 'b' partition.
> 
> gpart assigns partition letters in the order in which they're
> created.
> 
> Is there a way to specify which partition letter you want to
> create, or start with, or something?
> 
> Thanks, ==ml
> 

I just created a 10 GB file backed md device, and did some experiments
with gpart. Here's the result.

root at lazlar:/misc/cdrecorder/Film # gpart create -s MBR md0
md0 created
root at lazlar:/misc/cdrecorder/Film # gpart add -t freebsd md0
md0s1 added
root at lazlar:/misc/cdrecorder/Film # gpart create -s BSD md0s1
md0s1 created
root at lazlar:/misc/cdrecorder/Film # gpart add -b 16 -s 4G -t
freebsd-ufs -i 6 md0s1
md0s1f added
root at lazlar:/misc/cdrecorder/Film # gpart add -b 8388624 -t
freebsd-swap -i 2 md0s1
md0s1b added
root at lazlar:/misc/cdrecorder/Film # bsdlabel md0s1
# /dev/md0s1:
8 partitions:
#          size     offset    fstype   [fsize bsize bps/cpg]
  b:   12582816    8388624      swap
  c:   20971440          0    unused        0     0     # "raw" part,
don't edit
  f:    8388608         16    4.2BSD        0     0     0

It seems the partition letters can be assigned dynamically, using the
- -i option to gpart add.

Rolf
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