Posted 08 November, 2018
In a recovery of a system I found myself in annoying pickle of having two disks with a similar LVM layout and more precise with a equally named volume group. This can cause issues, however in my case it just stopped me from mounting the original device. To make matters worse the sizes of the volumes where nearly identically in size. Not really a user of LVM, it was time for google to save me.
Activating both identical volume failed :
[email protected]:~# vgchange -ay device-mapper: create ioctl on pve-swapLVM-Do7QVk4UeQXTTqVtB5b0pISJQy1YL1YJ4RB7lZXsAvYVGcYs9e7TZcFuHfkUBZJz failed: Device or resource busy device-mapper: create ioctl on pve-rootLVM-Do7QVk4UeQXTTqVtB5b0pISJQy1YL1YJgnTssDJJQj59LISgspFSLEH2pzqQLYw9 failed: Device or resource busy 1 logical volume(s) in volume group "pve" now active device-mapper: create ioctl on pve-dataLVM-46zXzJmc3xbdOtJdsVXrSlb5siaAacfRmhJ3Ac2ET7201zotB4DEX2kVu9gSafDC-tpool failed: Device or resource busy 2 logical volume(s) in volume group "pve" now active
So first thing I found was lvmdiskscan this will search for disk that are formatted with LVM. Not surprisingly I found two disks (new and old one) and a third data disk. (RAID)
[email protected]:~# lvmdiskscan /dev/sda2 [ 256.00 MiB] /dev/sda3 [ 465.51 GiB] LVM physical volume /dev/sdb2 [ 510.00 MiB] /dev/sdb3 [ 465.15 GiB] LVM physical volume /dev/sdc [ 29.10 TiB] 1 disk 2 partitions 0 LVM physical volume whole disks 2 LVM physical volumes
note : partition /dev/sda3 and /dev/sdb3 are dangerously similar !
Now we know that the partitions are very similar, however perhaps I might be lucky that the logical volumes where different lvscan :
[email protected]:~# lvscan inactive '/dev/pve/swap' [58.12 GiB] inherit inactive '/dev/pve/root' [96.00 GiB] inherit ACTIVE '/dev/pve/data' [295.03 GiB] inherit ACTIVE '/dev/pve/swap' [8.00 GiB] inherit ACTIVE '/dev/pve/root' [96.00 GiB] inherit inactive '/dev/pve/data' [338.60 GiB] inherit
note : there is a slight different in sizing of the volumes, this is good information. However the names are equal. This is causing the issue.
If we can change the volume group name (pve) this should be enough to mount it. However I don’t want to take the active ones, as that might crash my current system (?) So let’s check using vgdisplay :
[email protected]:~# vgdisplay --- Volume group --- VG Name pve System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 64 VG Access read/write VG Status resizable MAX LV 0 Cur LV 3 Open LV 0 Max PV 0 Cur PV 1 Act PV 1 VG Size 465.15 GiB PE Size 4.00 MiB Total PE 119078 Alloc PE / Size 114983 / 449.15 GiB Free PE / Size 4095 / 16.00 GiB VG UUID Do7QVk-4UeQ-XTTq-VtB5-b0pI-SJQy-1YL1YJ --- Volume group --- VG Name pve System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 7 VG Access read/write VG Status resizable MAX LV 0 Cur LV 3 Open LV 2 Max PV 0 Cur PV 1 Act PV 1 VG Size 465.51 GiB PE Size 4.00 MiB Total PE 119170 Alloc PE / Size 115075 / 449.51 GiB Free PE / Size 4095 / 16.00 GiB VG UUID 46zXzJ-mc3x-bdOt-JdsV-XrSl-b5si-aAacfR
Since there is a slight difference in size (449.51 vs 449.15) and I know the current disk in use is my new system (/dev/sda) (check using df -h).
I know I need /dev/sdb3 with 465.15 GB in size, this is the first in the list with UUID (Do7QVk-4UeQ-XTTq-VtB5-b0pI-SJQy-1YL1YJ)
Finally we know what we want to rename, it seems almost too simple using vgrename :
[email protected]:~# vgrename Do7QVk-4UeQ-XTTq-VtB5-b0pI-SJQy-1YL1YJ pveb Processing VG pve because of matching UUID Do7QVk-4UeQ-XTTq-VtB5-b0pI-SJQy-1YL1YJ Volume group "Do7QVk-4UeQ-XTTq-VtB5-b0pI-SJQy-1YL1YJ" successfully renamed to "pveb"
After this we can activate the volume group using vgchange :
And voila one can mount the new device :
mkdir -p /data/oldroot mkdir -p /data/data mount /dev/pveb/root /data/oldroot mount /dev/pveb/data /data/data
Tadaaa ! The data is available once more 🙂
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