Upgrade 2012R2 Core to 2016 Core blank window

I usually do release upgrades over VPN, so I've tried this a few times. Whenever it updates my openvpn package I lose connection, so I reconnect afterwards.

do-release-upgrade starts a backup SSH session on port 1022 and a backup screen session. If you do not have screen installed this will NOT be available.

You can get the screen session by running:

sudo screen -list
There is a screen on:
    2953.ubuntu-release-upgrade-screen-window   (09/13/2012 04:48:02 AM)    (Detached)
1 Socket in /var/run/screen/S-root.

Then to reattach do:

sudo screen -d -r root/2953.ubuntu-release-upgrade-screen-window

Using the previously listed screen after root/

You should be back to where you lost connection.

I've managed to upgrade without any further problems a long the way by doing this things:

• Don't install updates when asked about in the setup step
• Pulled the LAN cable after the setup prepared the machine and restarted for the first time.

I can't really recommend this solution based on facts. But in my case it did work flawlessly without any issues after the upgrade.