Comment 51 for bug 1396213

im not sure, but looks the problem i have here is the same problem 14.04

gave up waiting for root device
common problems:
--boot arts (cat /proc/cmdline)
-check root delay (did the system wait long enough?)
-check root (did the system wait for the right device?)
-missing modules ls/dev
ALERT! /dev/mapper/ubuntu-vg-root noes not exist!
droping to a shell.
budt box 1.21.1 (ubuntu 1.1.21.0-1ubuntu1) built-in-shell (ash)
enter 'help' for a list of built-in- commants
(initramfs)

on a live cd>

ubuntu@ubuntu:~$ sudo lvm lvscan
  ACTIVE '/dev/ubuntu-vg2/root' [929.36 GiB] inherit

ubuntu@ubuntu:~$ sudo mkdir /newroot
ubuntu@ubuntu:~$ sudo mount /dev/ubuntu-vg2/root /newroot
mount: special device /dev/ubuntu-vg2/root does not exist