This is a random issue that you might run into on Ubuntu 16.04 with Plesk install. It has been fixed for newer images as of Jun, 5th 2018.
- Load Knoppix or Gparted to your DVD drive from the cloud panel.
- Mount your partitions using the following guide: https://unsrewiki.1sys1.com/index.php/2019/05/13/unable-to-mount-lvm2_member/
3. chroot to mnt.
# chroot /mnt
4. Disable apparmor and you will get the odd output bellow, but don’t worry it means it worked:
# systemctl disable apparmor apparmor.service is not a native service, redirecting to systemd-sysv-install Executing /lib/systemd/systemd-sysv-install disable apparmor insserv: warning: current start runlevel(s) (empty) of script
apparmor' overrides LSB defaults (S). insserv: warning: current stop runlevel(s) (S) of scriptapparmor’ overrides LSB defaults (empty).
5. Eject the DVD from the server and reboot back to local and server should boot right up.