LVM recovery

[Guest42]

Somebody at at the office needs us to recover information of of a linux HD that won't boot, so we plugged it into our Redhat machine, and the partitions on it are as follows:

/dev/sdb1 - boot
/dev/sdb2 - swap
/dev/sdb3 - LVM

Unfortunately, since all the infomation about the volume groups in that LVM are part of the LVM itself, I'm screwed. I'd have to recover the LVM to get the info I need to recover the LVM! Is there any other way of doing this? I reckon the underlying structure of the LVM is still intact, and in grub I can see the line root="/dev/VolGroup00/vol1root". Can I use this information to mount that group, somehow?

Thanks for your time
-Guest42

 

[ady2k]

Yes, You can mount it if you are sure with logical volume name.
Good Luck...

 

[Annihilannic]

Have you tried vgscan to scan for LVM disk groups? Read the man vgscan page for details.

Annihilannic.

 

[Guest42]

None of that really help. The thing is, Redhat's hardware browser shows that there's an LVM on the partition, but LVM itself doesn't recognize it. I set LVM to level 3 verbosity, and it says that sdb3 has no label, so... I don't know if there's someway I can make LVM point to the data.

 

[marsd]

Okay. There are three logical layers to LVM: physical, volume,
and logical. If you use pvscan,vgscan,and lv? to decipher your problem and then have questions, please let us know. Please post error messages and other errata.

In the meantine:

http://www.tldp.org/HOWTO/LVM-HOWTO/

 

[Guest42]

Actually, it just wasn't seeing the VolumeGroups no way no how, which meant that unless we dumped out the raw data onto another drive and sorted it out, the partition was basically trashed. We decided it wasn't worth it. It seems like a really weird issue, but LVM basically messed up bad.

What I don't understand is why LVM overwrites the ability for Linux to see the data as plain partitions. If I were designing it, I would have a file in the top directory of each partition that tells LVM to create pointers to certain chunks of data, rather than buggering up partition tables. But I'm no linux guy, so I don't know how reasonable of an idea that is.

 

[Annihilannic]

If I recall when setting up LVM you had the choice of using partitions on the disk or the entire disk... so it may have been a choice made by the admin when originally configuring it. Either way it shouldn't affect the recoverability of the data.

Annihilannic.