|
|
|
|
# lvmmerge - dracut module
|
|
|
|
|
|
|
|
|
|
## Preparation
|
|
|
|
|
- ensure that the lvm thin pool is big enough
|
|
|
|
|
- backup any (most likely /boot and /boot/efi) device with:
|
|
|
|
|
```
|
|
|
|
|
# mkdir /restoredev
|
|
|
|
|
# dev=<device>; umount $dev; dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev"); mount $dev
|
|
|
|
|
```
|
|
|
|
|
- backup the MBR
|
|
|
|
|
```
|
|
|
|
|
# dev=<device>; dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev") bs=446 count=1
|
|
|
|
|
# ls -l /dev/disk/by-path/virtio-pci-0000\:00\:07.0
|
|
|
|
|
lrwxrwxrwx. 1 root root 9 Jul 24 04:27 /dev/disk/by-path/virtio-pci-0000:00:07.0 -> ../../vda
|
|
|
|
|
```
|
|
|
|
|
- backup some partitions
|
|
|
|
|
```
|
|
|
|
|
# dev=/dev/disk/by-path/virtio-pci-0000:00:07.0
|
|
|
|
|
# dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev") bs=446 count=1
|
|
|
|
|
# umount /boot/efi
|
|
|
|
|
# dev=/dev/disk/by-partuuid/687177a8-86b3-4e37-a328-91d20db9563c
|
|
|
|
|
# dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev")
|
|
|
|
|
# umount /boot
|
|
|
|
|
# dev=/dev/disk/by-partuuid/4fdf99e9-4f28-4207-a26f-c76546824eaf
|
|
|
|
|
# dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev")
|
|
|
|
|
```
|
|
|
|
|
Final /restoredev
|
|
|
|
|
```
|
|
|
|
|
# ls -al /restoredev/
|
|
|
|
|
total 1253380
|
|
|
|
|
drwx------. 2 root root 250 Jul 24 04:38 .
|
|
|
|
|
dr-xr-xr-x. 18 root root 242 Jul 24 04:32 ..
|
|
|
|
|
-rw-------. 1 root root 209715200 Jul 24 04:34 dev-disk-by\x2dpartuuid-4fdf99e9\x2d4f28\x2d4207\x2da26f\x2dc76546824eaf
|
|
|
|
|
-rw-------. 1 root root 1073741824 Jul 24 04:34 dev-disk-by\x2dpartuuid-687177a8\x2d86b3\x2d4e37\x2da328\x2d91d20db9563c
|
|
|
|
|
-rw-------. 1 root root 446 Jul 24 04:38 dev-disk-by\x2dpath-virtio\x2dpci\x2d0000:00:07.0
|
|
|
|
|
```
|
|
|
|
|
- make a thin snapshot
|
|
|
|
|
```
|
|
|
|
|
# lvm lvcreate -pr -s rhel/root --name reset
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
- mark the snapshot with a tag
|
|
|
|
|
```
|
|
|
|
|
# lvm lvchange --addtag reset rhel/reset
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
- remove /restoredev
|
|
|
|
|
```
|
|
|
|
|
# rm -fr /restoredev
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## Operation
|
|
|
|
|
|
|
|
|
|
If a boot entry with ```rd.lvm.mergetags=<tag>``` is selected and there are LVs with ```<tag>```
|
|
|
|
|
dracut will
|
|
|
|
|
- make a copy of the snapshot
|
|
|
|
|
- merge it back to the original
|
|
|
|
|
- rename the copy back to the name of the snapshot
|
|
|
|
|
- if /restordev appears in the root, then it will restore the images
|
|
|
|
|
found in that directory. This can be used to restore /boot and /boot/efi and the
|
|
|
|
|
MBR of the boot device
|
