@Marco-Ceppi 's solution is already integrated into
When you run
do-release-upgrade it starts a screen session automatically. If your ssh session gets disconnected, you can resume the installation. All you have to do is open a new ssh session, and run
do-release-upgrade again. It will reconnect to your previous installation.
A second risk, pointed out by @sepp2k is that your sshd server might need to be upgraded, and it could perhaps not restart correctly. Therefore the upgrade program runs a second deamon, at the port specified. You should check your network configuration to make sure you have access through this port, before resuming.
Moreover, the screen-session
do-release-upgrade starts by itself is run under root account, so IF you own screen-session crashes, you will be able to recover by running
sudo screen -x, if (for some reason) the command
do-release-upgrade doesn't recover it by itself, which seems to be common.