So after recovering a box which had a controller failure we needed to mount the old fs to recover some stuff.
when trying to mount /dev/sdc2 we got:
mount: unknown filesystem type ‘LVM2_member’
fix is easy :
modprobe dm-mod
vgchange -ay
lvscan now yields:
ACTIVE '/dev/VolGroup/lv_root' [50.00 GiB] inherit ACTIVE '/dev/VolGroup/lv_home' [178.46 GiB] inherit ACTIVE '/dev/VolGroup/lv_swap' [3.94 GiB] inherit
mount /dev/VolGroup/lv_root /mnt/tempdisk/
et viola` !!
nJoy 😉