Comment 3 for bug 1790535

Upgraded from 16.04LTS to 18.04 (followed published instructions
  - https://linuxconfig.org/how-to-upgrade-to-ubuntu-18-04-lts-bionic-beaver).
Upgrade failed (dpkg: error processing package systemd-shim (--remove)
Upgrade was aborted (error processing packages executed)
System basically unusable after completion (many pgms/services failed, unable to open new terminal).
System would not reboot successfully.
Rebooted to Recovery Mode, attempted to fix (apt-get) - no change.
Restored to back-up state.
(Upgrade Terminal Session attached.)