what is the proper way to mount a LVM image that is mirrored?

Question

I have an Ubuntu upgrade that ended up not working -- 19.04 to 19.10 (see post for more info).

Now I need to mount my root image to edit files on it, and rebuild Grub, in the hopes of getting it back.

However, I am uncertain how to properly mount the image. My root image is mirrored on two separate PV's.

Running sudo fdisk -l | grep /dev/ I'm getting:

(Note: I used ... to abbreviate parts of the output.)

Disk /dev/loop0: ... sectors
Disk /dev/loop1: ... sectors
  ...
Disk /dev/sda: ... sectors
     /dev/sda1 ... 930.7G Linux LVM
     /dev/sda2 ...   800M Linux
Disk /dev/sdb: ... sectors
     /dev/sdb1 ... 465.8G Linux LVM
Disk /dev/mapper/ubuntu--vg-root_mlog: 4 MiB ... sectors
Disk /dev/mapper/ubuntu--vg-root_mimage_0: 214 GiB ... sectors
Disk /dev/mapper/ubuntu--vg-root_mimage_1: 214 GiB ... sectors
Disk /dev/mapper/ubuntu--vg-root: 214 GiB ... sectors
  ...

Should I be using /dev/mapper/ubuntu--vg-root to mount my root image so that the mirror stays intact?

Answer 1

Should I be using /dev/mapper/ubuntu--vg-root to mount my root image so that the mirror stays intact?

Yes sir.

It looks like, even if quite broken, your system launched the LVM stuff and your PV/VG/LV has been correctly detected. So just mounting your LV will work and keep your mirror synchronized.