[linux-lvm] Please help me recover my LVM configuration

[linux-lvm] Please help me recover my LVM configuration

[David Ziring]

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Hi all, 

I’m hoping I can get some help recovering my data.  A week or so back I accidentally overwrote the partition table on one of the two drives containing my data.  I luckily didn’t touch the partition itself, so I believe all the data is still there, but in rebuilding the partition table I (think I) nuked the uuid of the drive.  Now I’m not sure how to progress.  
Please help this relative neophyte – there is a lot of nostalgia sitting on those drives.  Tell me what information you need and I will get it.

DZ

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Re: [linux-lvm] Please help me recover my LVM configuration

[evilensky]

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On Jul 29, 2011, at 10:30 PM, David Ziring wrote:

> Hi all,
>  
> I’m hoping I can get some help recovering my data.  A week or so back I accidentally overwrote the partition table on one of the two drives containing my data.  I luckily didn’t touch the partition itself, so I believe all the data is still there, but in rebuilding the partition table I (think I) nuked the uuid of the drive.  Now I’m not sure how to progress.  


If all that is over-written is the partition table, testdisk (http://www.cgsecurity.org/wiki/TestDisk) is about the simplest partition recovery solution I've found.

-Ev


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Re: [linux-lvm] Please help me recover my LVM configuration

[Ray Van Dolson]

On Fri, Jul 29, 2011 at 08:30:25PM -0700, David Ziring wrote:
> Hi all,
>  
> I’m hoping I can get some help recovering my data.  A week or so back I
> accidentally overwrote the partition table on one of the two drives containing
> my data.  I luckily didn’t touch the partition itself, so I believe all the
> data is still there, but in rebuilding the partition table I (think I) nuked
> the uuid of the drive.  Now I’m not sure how to progress. 
> Please help this relative neophyte – there is a lot of nostalgia sitting on
> those drives.  Tell me what information you need and I will get it.
>  
> DZ

Was the lost partition also the one housing /etc/lvm?  If not, you can
get the UUID that way....

If it was, fortunately LVM keeps metadata information about itself.
You should able to dump it via:

     dd if=/dev/sda2 bs=512 count=255 skip=1 of=/tmp/sda2.txt

Where /dev/sda2 is your LVM partition.

You can then examine the output file with "strings" and pull out the
UUID information or even completely recreate your configuration files.

What I have done in the past is to just examine this information and
then use dmsetup to create a temporary device, mount it and copy out
the information from /etc/lvm.

Then it's the standard vgcfgrestore dance...

Dumped some instructions from a work wiki here that may be of help
(sorry it's PDF):

    http://www.bludgeon.org/~rayvd/files/LVM_Missing_Metadata.pdf

Ray

Re: [linux-lvm] Please help me recover my LVM configuration

[David Ziring]

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Following up on this message, I don’t want anyone to think I’m asking for help without doing my own research.  

I found  a set of instructions at http://www.barryodonovan.com/index.php/2007/12/08/lvm-recovery and it’s similar to my problem (although my physical volume is on a partition instead of the entire disk) and I want to make sure that the plan to repair my system won’t wipe existing data.

So, assuming the data is still on /dev/sdc1, if I recreate the PV, will I lose data?  i.e., will pvcreate –vvvv –u <my uuid> /dev/sdc1 destroy the data on the partition?
Similiarly, will vgcreate –v <my volumename> /dev/sdc1 kill my data?

Am I heading in entirely the wrong direction?

Thanks,
DZ

From: David Ziring 
Sent: Friday, July 29, 2011 8:30 PM
To: linux-lvm@redhat.com 
Subject: Please help me recover my LVM configuration

Hi all, 

I’m hoping I can get some help recovering my data.  A week or so back I accidentally overwrote the partition table on one of the two drives containing my data.  I luckily didn’t touch the partition itself, so I believe all the data is still there, but in rebuilding the partition table I (think I) nuked the uuid of the drive.  Now I’m not sure how to progress.  
Please help this relative neophyte – there is a lot of nostalgia sitting on those drives.  Tell me what information you need and I will get it.

DZ

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Re: [linux-lvm] Please help me recover my LVM configuration

[Eugene Vilensky]

On Sat, Jul 30, 2011 at 5:06 PM, David Ziring <zeke@thebayou.net> wrote:
> So, assuming the data is still on /dev/sdc1, if I recreate the PV, will I
> lose data?� i.e., will pvcreate �vvvv �u <my uuid> /dev/sdc1 destroy the
> data on the partition?
> Similiarly, will vgcreate �v <my volumename> /dev/sdc1 kill my data?

David,

If all that you have destroyed is the partition table, you may be able
to simply recover that appropriately, reboot, and vgscan everything
back into place.  If you still have your partition table intact�if
there is more extensive damage, Ray has shared about as detailed
instructions as one can find on a mailing list for a class of problem.

I wouldn't go about re-creating anything until you've ascertained what
has been lost, which is slightly unclear from your mailings.

-Ev