I had a development desktop fail and had to extract the data from the LVM managed hard drive. Easy, right? Pull out the drive, hook it up to an enclosure, plug into a laptop USB port and suck all the data down. And typically, it wasn’t that simple. The following error message appeared:
# mount /dev/sdb1 /mnt unknown filesystem type lvm2_member
Blast. Turns out, this disk has been part of an LVM volume group and the laptop didn’t know anything about this configuration. The solution, fortunately, is simple.
Install LVM, if it isn’t already:
# apt-get install lvm2
List physical volumes, and their labelled volume groups:
# pvs PV VG Fmt Attr PSize PFree /dev/sdb1 VolGroup01 lvm2 a- 27.95g 22.95g
There’s a volume group, VolGroup01, which I do vaguely remember configuring. So, scan for this, make active, scan for logical volumes and mount. That’s it, like so:
# vgscan Reading all physical volumes. This may take a while... Found volume group "VolGroup01" using metadata type lvm2 # vgchange -a y VolGroup01 1 logical volume(s) in volume group "VolGroup01" now active # lvscan ACTIVE '/dev/VolGroup01/dataVol00' [5.00 GiB] inherit # mount /dev/VolGroup01/dataVol00 /mnt
And now the data on the stray disk is available, mounted under /mnt. Do with it what you will.
Matt Parsons is a freelance Linux specialist who has designed, built and supported Unix and Linux systems in the finance, telecommunications and media industries.
He lives and works in London.