[linux-lvm] Altering a Physical Volume's UUID

[linux-lvm] Altering a Physical Volume's UUID

[Mark Krenz]

  Hi,  I'm using LVM with Xen virtual machines by creating sparse image
files with something like 

  dd if=/dev/zero of=diskimage bs=1 count=1 seek=1073741824

 Then I use a loopback device to use the diskimage as a block device and
create a physical volume, volume group and logical volumes on it.

  This all works great, but when I copy the diskimage file to another
file and try to setup a loopback device for it, I get complaints about
there being multiple identifical UUIDs for physical volumes and volume
groups.


  So is there a way to change the UUID of a physical volume and volume
group?


  If you are wondering why I would need to copy the diskimage file, its
because I'm setting up Xen template images for different OSes that I can
then simply copy into place, make a few modifications and then be on my
way.

-- 
Mark S. Krenz
IT Director
Suso Technology Services, Inc.
http://suso.org/

Re: [linux-lvm] Altering a Physical Volume's UUID

[Luca Berra]

On Fri, Sep 08, 2006 at 12:55:06PM +0000, Mark Krenz wrote:
>  So is there a way to change the UUID of a physical volume and volume
>group?
>
i'd try with vgcfgbackup, sed, pvcreate, vgcfgrestore.

L.

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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Re: [linux-lvm] Altering a Physical Volume's UUID [solved]

[Mark Krenz]

  Hey, that works!  Thank you very much Luca.  For other people's
benifit that may find this in a search, here is what I did:

This assumes that you ALREADY have a disk file called lvmdisk1 with lvm partitions on it

# losetup /dev/loop0 lvmdisk1
# vgscan
# vgcfgbackup -f TemplateVG.cfg TemplateVG

Now edit TemplateVG.cfg file and change the IDs for the volume group,
physical volume and logical volumes too.  I made it easy by just
incrementing the last character by one, a becomes b, x becomes y, etc.
Keep track of what ID you gave the physical volume.

# vgchange -a n TemplateVG 

Now run pvcreate using the --uuid option and use the NEW uuid that you
generated an changed to in the VG config file.

# pvcreate -ff --uuid CFhjSe-EqSc-pnDz-4UcP-ylxh-hcY6-oV6BGR --restorefile TestDiskVG.cfg /dev/loop2

It will complain that it couldn't find the physical volume with the
specified uuid, but it will still create the physical volume.


# vgcfgrestore -f TemplateVG.cfg TemplateVG

# vgchange -a y TemplateVG

That's it, now you can change the volume group name if that's what you
need to do.  You should try mounting one of the logical volumes now to
make sure the data is still in tact.




On Fri, Sep 08, 2006 at 03:35:10PM GMT, Luca Berra [bluca@comedia.it] said the following:
> On Fri, Sep 08, 2006 at 12:55:06PM +0000, Mark Krenz wrote:
> > So is there a way to change the UUID of a physical volume and volume
> >group?
> >
> i'd try with vgcfgbackup, sed, pvcreate, vgcfgrestore.
> 
> L.
> 
> -- 
> Luca Berra -- bluca@comedia.it
>        Communication Media & Services S.r.l.
> /"\
> \ /     ASCII RIBBON CAMPAIGN
>  X        AGAINST HTML MAIL
> / \
> 
> _______________________________________________
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> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/


-- 
Mark S. Krenz
IT Director
Suso Technology Services, Inc.
http://suso.org/