[linux-lvm] Help restoring a corrupted PV partition ( 18th )

Zdenek Kabelac zkabelac at redhat.com
Mon Oct 18 21:40:39 UTC 2021

Dne 18. 10. 21 v 20:08 Brian McCullough napsal(a):
> I have had a disk go bad on me, causing me to lose one PV.
> If I am not providing sufficient, or the proper, information, feel free
> to ask for more.
> I seem to have retrieved the partition using ddrescue and put it on to
> a new drive, but it seems to be missing some label information, because
> pvscan doesn't recognize it as a PV partition.
> Using hexdump, I see the string " LVM2 " at 0x1004, but nothing before
> that.  The whole 16 bytes is:
> 0x01000  16 d6 8e db 20 4c 56 4d  32 20 78 5b 35 41 25 72
>                          L  V  M  2
> I find what appears to be an LVM2 vgconfig block starting at 0x01200,
> extracted that to a file and was able to read the UUID that this PV
> should have.  It is one of about a dozen that make up this VG.
> On another machine, I dumped a PV partition, and find "LABLEONE" at
> 0x200, with the same " LVM2 " at 0x01000.
> I was concerned that my dump was offset, but the comparison to the
> "good" one suggests that that isn't the problem, but just the missing
> "LABLEONE" and related information at 0x0200.
> How to fix?
> If I do a "pvcreate --uuid xxxx" would this fix that recovered partition
> so that pvscan and friends can work properly, and I can finally boot
> that machine?


It's quite important to be aware how the disk corruption happened.
Was this plain disk hw error -  or some crash of raid setup ?

Normally you could restore PV with this:

pvcreate --uuid  XXXX --restorefile  file_with_vg_backup  /dev/ddddd
vgcfgrestore --restorefile   file_with_vg_backup   vgname

But if the content of device was scramble by some 'raid' bug - you might have 
problem to retrieve any usable data afterward.



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