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[linux-lvm] Re: lvm partition on lv

Markus Laire wrote:
On 8/8/06, Markus Laire <malaire gmail com> wrote:

On 8/8/06, Randall Smith <randall tnr cc> wrote:
> Let's say on /dev/vg1/test I had one LVM partition and one ext3
> partition.  How can I access those separate partitions since it's only
> one device (/dev/vg1/test)?  Normally, a partitioned block device
> (/dev/hda) would show up like /dev/hda1, dev/hda2, etc.

With loop-device, you can use only part of the block-device as new
block-device (See options -o and -s in man:losetup)

So if you know the positions where the partitions start, and their
lengths (both in bytes), you could do something like this: (I havn't
tested this, so there might be some errors in these commands. But the
basic idea should work)

# make LVM partition available at /dev/loop1
losetup -o $lvm_start -s $lvm_size /dev/loop1 /dev/vg1/test
mkdir /mnt/test
# Mount ext3-partition at /mnt/test using loop-device
mount -t ext3 -o offset=$ext3_start,sizelimit=$ext3_length
/dev/vg1/test /mnt/test

Well, last command is missing at least "loop" option - i.e. it should be

mount -t ext3 -o loop,offset=$ext3_start,sizelimit=$ext3_length
/dev/vg1/test /mnt/test

or you could use these instead
losetup -o $ext3_start -s $ext3_length /dev/loop2 /dev/vg1/test
mount -t ext3 /dev/loop2 /mnt/test

I hope I didn't make other mistakes...

($lvm_size and $ext3_length both means the size of the partition in
bytes - I should've used 'size' or 'length' for both for consistency)

Thanks.  That's perfect.

Working with Unix is so much fun. It always seems that anything is possible as long as I'm willing to learn something new.


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