Re: [gentoo-user] rescuing lvm data

[Florian Philipp]

Am 24.10.2012 22:08, schrieb Stefan G. Weichinger:
>
> greetings ...
>
> the server in my basement is driving me nuts ... and I start making
> mistakes ... sigh
>
> It had a LVM volume group ... consisting of two PVs ...
>
> The question in short:
>
> if I only have one PV at hand, which contains all the PEs of a given LV
> ... (how) am I able to extract/export/read the contents of that LV?

So you still have the volume group metadata, just not one of the PVs, right?

>
> background:
>
> when I searched for the reason of those crashes, I removed and swapped
> and cloned hard disks all around.
>
> Right now I am on a brand new machine and want to sort out harddisks etc.
>
> One PV wasn't detected correctly ("unknown device") even though it had
> the correct uuid. I did some "pvcreate -u" on it ... and now those LVs
> on it aren't accessible anymore (can't mount or even fsck).
>
> My luck (I hope!): I have a clone of that harddrive.
>
> But I don't want to simply plug it in because I fear to ruin things as I
> already messed up that VG further by trying stuff like vgcfgrestore etc.
>
> Yes, my fault.
>
> The clone contains all the blocks for an LV I would like to keep
> somehow. So I assume it should be possible to access them?
>

First things first: If you can, make a disk dump of every affected HDD
or at least back up the metadata with vgcfgbackup.

Have you tried activating the volume group with --partial (see `man
lvm`). Something along the lines of `lvchange --partial -a y`).

If that doesn't help, maybe `vgreduce --removemissing --force` will do
the job.

Hope this helps,
Florian Philipp