LVM record every LVM VG and LV metadata operation and save it to /etc/lvm/backup automatically, old version backup files are archived to /etc/lvm/archive.
The backup file can be used to rollback LVM metadata changes, for example, if you have removed the VG/PV or even re-initialize disk with pvcreate, don’t panic, as long as file system was not re-created, you can use vgcfgrestore to restore all the data.
The following is to demonstrate how to recover a LV after it is completed destroyed from PV level (pvremove)
1. Create test LV and write some data
# pvcreate /dev/sdb1 /dev/sdb2 Physical volume "/dev/sdb1" successfully created Physical volume "/dev/sdb2" successfully created # vgcreate vg01 /dev/sdb1 /dev/sdb2 Volume group "vg01" successfully created # lvcreate -L100M -n lv01 vg01 Logical volume "lv01" created # mkfs.ext3 /dev/vg01/lv01 # mount /dev/vg01/lv01 /mnt/ # cp /etc/hosts /mnt/ # ls /mnt/ hosts lost+found
2. Destroy LV, VG and PV
# vgremove vg01 Do you really want to remove volume group "vg01" containing 1 logical volumes? [y/n]: y Do you really want to remove active logical volume lv01? [y/n]: y Logical volume "lv01" successfully removed Volume group "vg01" successfully removed # pvcreate /dev/sdb1 /dev/sdb2 Physical volume "/dev/sdb1" successfully created Physical volume "/dev/sdb2" successfully created
3. Lets recover the LV and the data
Find out the backup file to restore from
# vgcfgrestore -l vg01 .. file: /etc/lvm/archive/vg01_00002.vg VG name: vg01 Description: Created *before* executing 'vgremove vg01' Backup time: Tue May 10 15:41:31 2011
First attempt failed, because PV UUID is changed
# vgcfgrestore -f /etc/lvm/archive/vg01_00002.vg vg01 Couldn't find device with uuid 'pVf1J2-rAsd-eWkD-mCJc-S0pc-47zc-ImjXSB'. Couldn't find device with uuid 'J14aVl-mbuj-k9MM-63Ad-TBAa-S0xF-VElV2W'. Cannot restore Volume Group vg01 with 2 PVs marked as missing. Restore failed.
Find old UUID
# grep -B 2 /dev/sdb /etc/lvm/archive/vg01_00002.vg
pv0 {
id = "pVf1J2-rAsd-eWkD-mCJc-S0pc-47zc-ImjXSB"
device = "/dev/sdb1" # Hint only
--
pv1 {
id = "J14aVl-mbuj-k9MM-63Ad-TBAa-S0xF-VElV2W"
device = "/dev/sdb2" # Hint only
Recreate PV with the old UUID
# pvcreate -u pVf1J2-rAsd-eWkD-mCJc-S0pc-47zc-ImjXSB /dev/sdb1 Physical volume "/dev/sdb1" successfully created # pvcreate -u J14aVl-mbuj-k9MM-63Ad-TBAa-S0xF-VElV2W /dev/sdb2 Physical volume "/dev/sdb2" successfully created
Run vgcfgrestore again
# vgcfgrestore -f /etc/lvm/archive/vg01_00002.vg vg01 Restored volume group vg01
Data was also recovered
# mount /dev/vg01/lv01 /mnt/ mount: special device /dev/vg01/lv01 does not exist # lvchange -a y vg01/lv01 # mount /dev/vg01/lv01 /mnt/ # cat /mnt/hosts 127.0.0.1 localhost