[linux-lvm] lvm2 confused about double UUID

Ron Johnson ron.l.johnson at cox.net
Mon Jul 27 06:19:17 UTC 2009

On 2009-07-26 22:30, Christian Kujau wrote:
> On Sun, 26 Jul 2009 at 21:55, Ron Johnson wrote:
>> So the issue seems really the deeper fact that you've got two physical devices
>> with the same UUID.  All your lvm issues tumble out from there.
>> Is that a good summary?
> Yes, that's it. I know, having 2 physical volumes with the same UUID is 
> not cool and is certainly not supported, but due to the split that's what 
> I have here now and I assumed that I could convince LVM via the filter 
> directive to use a certain device for vg02. I mean, vg02 is working fine, 
> but I really want to format either sdb or sdc, but I'm afraid of 
> destroying something in the LVM layout...
> Let me ask another thing: when I assume for a moment that "pvs" is lying 
> and really sdc is used for vg02, I'd go ahead and 1) pvcreate sdb, thus 
> assigning a new UUID to sdb and 2) remove the filter from lvm.conf. LVM 
> should not complain any more (since we have 2 different UUIDs now) and I/O 
> still goes to sdc, as it is now apparently. If things go wrong, how can I 
> restore the LVM header on sdb? (Would "pvcreate --uuid <old-UUID>" do the 
> trick? Or restoring with dd? How many bytes are changed when using 
> pvcreate?)

Now you're getting beyond my pay grade.

But with uuidgen and tune2fs, you could give sdc1 a new UUID.  That 
would hose lvm, though, and you'd have to do surgery in /etc/lvm.

I'd go the safe/sure route and backup sdc2 if possible (have you 
written anything new to it since breaking the mirror?), and start 
over, dropping it from lvm. refdisking it (is there such a word?), 
etc, etc.

Scooty Puff, Sr
The Doom-Bringer

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