[linux-lvm] pvcreate on a loopback device - error: (newbie)

[Markus Laire]

On 9/20/06, John Que <qwejohn at gmail.com> wrote:
> Hello,
>
> I had tried to do some test with LVM on a loopback device
> follwing some tutorials on the web.
>
> I get errors.
> what I do is this:
>
> dd if=/dev/zero of=/work/tmp/disk-image count=10240
> mke2fs /work/tmp/disk-image
> mount -o loop /work/tmp/disk-image /work/loop/    78  14:23
>
> pvcreate /dev/loop1
>
> error:
>  Failed to wipe new metadata area
>   /dev/loop1: Format-specific setup of physical volume failed. Failed
> to setup physical volume "/dev/loop1"
>
>
> what did I do wrong ?

If you want to use LVM on a loopback device, you don't create a
filesystem on it first.

You need to do something like
  # Create new empty disk-image
  dd if=/dev/zero of=disk-image count=10240
  # set up a loop-device for it
  losetup /dev/loop2 disk-image
  # initialize that loop-device for LVM
  pvcreate /dev/loop2
  # Create a VG on it
  vgcreate Test /dev/loop2

Now you can create Logical Volumes on that VG, e.g.:
  # Create a logical volume
  lvcreate --size 4M --name MyLV Test
  # Create a filesystem on it
  mke2fs /dev/Test/MyLV
  # mount the filesystem
  mkdir MyLV
  mount /dev/Test/MyLV MyLV

And if you want to remove everything...
  umount MyLV
  rmdir MyLV
  lvremove /dev/Test/MyLV
  vgremove Test
  losetup -d /dev/loop2
  rm disk-image

-- 
Markus Laire