[linux-lvm] recovering volumes

[Joel Rees]

For the record:

I finally had a full day or two that I could sit quietly and think. I  
noticed on /. last night that some people were mentioning Christophe  
Grenier's photorec as a tool for digging out image files, so I  
downloaded it last night and it did find all my files in the lost  
physical partition that I had attached to the botched volume group.  
All 70,000+ of them, scattered across 170 or so directories. Had to  
sacrifice a partition I'd been playing with freebsd in to hold the 11G 
+ of recovered files.

The photorec download comes with testdisk, which can find blown  
partitions, so I played with that as well. It saw the missing LVM  
partitions. I'm not sure if writing the results on the disk with the  
main volume group (/hda2) helped or not, but finding them was re- 
assuring, and this morning I was able to recover the volumes  
completely. (Yeah, psychological, I know.)

The way I did it was to sacrifice the remains of an old install of  
FC4 in another partition on /hda to install a second (very minimal)  
FC5 in a single base partition, no LVM. Then I booted back up in FC6  
on /hde2 to edit /boot/grub/grub.conf in the boot partition in /hda1  
so that grub would see the new install of FC5. Then I booted the new  
FC5 and started reading the man for lvm again.

pvdisplay, I think it was, saw the missing physical volumes.

So I mounted the old boot partition under /oldfc5 and cd-ed into / 
oldfc5/etc/lvm and looked at the stuff in backup and archive. The  
uuids in the most recent archive of the lost fc5 volume group and the  
backup were the same.

So I did a pvcreate --restorefile backup/fc5 --uuid <long uuid> /dev/ 
hde3 to re-create the physical volume on the other disk. It  
complained that it didn't find the physical volume, but then it said  
volume created.

So I continued with a pvcreate --restorefile backup/fc5 --uuid <other  
long uuid> /dev/hda2 and this time it created the physical volume  
with no complaints.

So I did the vgcfgrestore --file backup/fc5 (I think it was, too bad  
I didn't save the shell.) and that gave me a message that indicated  
success. So I looked at the file system with the graphical lvm  
manager widget and it now showed all my lost logical partitions.

I had to get rid of some cruft in /etc/fstab for the old fc5, but it  
boots, and all my files are there.

I'm probably leaving out a step or two, I really should have saved  
the text of the terminal session so I would have a record.

I haven't tried booting FC6 to see if it survived the process.

On 2006/12/24, at 18:40, Joel Rees wrote:

> Using Fedora Core 5 I had a volume group on /dev/hda3 and added a  
> logical volume on /dev/hde3. Didn't read the how to, didn't know  
> it's a no-no. Decided to play with Ubuntu, and thought I'd set up  
> logical volumes for it on /dev/hde2. Apparently, I wiped out the  
> headers on /dev/hde3 and then the entire logical group for FC5  
> refused to mount. In attempting to recover the headers I've  
> apparently wiped out the headers for the whole volume group --  
> pvcreate using a recovery option or something that I failed to  
> follow with some generate command, if I remember right. Also, I set  
> up a volume group on /dev/hde2 and loaded FC6 into that since I was  
> feeling burned by Ubuntu at the time.
>
> Any guesses at how badly I'm screwed? or pointers to more  
> information than can be found on the how-to pages?
>
> Not really life-or-death data lost, but I had been using it to back  
> up the digital camera and there were about a months worth of my  
> kids experiments that I don't have a backup of. Also, it would be a  
> useful exercise for me, in terms of gaining confidence in lvm, if  
> there were some way to recover the headers just from the stuff in / 
> etc/lvm .
>
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