On Ubuntu there is a cool feature if you have ssh'd into a computer and are doing a 'sudo do-release-upgrade' and trying to move to the next version via ssh but lose connection, you can then get back to it either by the console of via another new ssh session after reconnecting. On ubuntu you type “sudo screen -D -r” when wanting to get back to that.
This is actually possible for anyone and you can do the same thing on any distro by setting up screen as you login. So for example if you ssh to a server, then just run the command 'screen' first as you login. Now if you ever get disconnected there will be a screen process that you can reattach to anytime. Just log back in either via new ssh session or the console and type 'screen -r' if logged in as the same user, or sudo first if you are not.
Pretty basic and can save you a nightmare if apt-get is waiting for input and gotten stuck mid way through an upgrade or something :)
If you don't have screen installed you can also use byobu which does the same thing but is newer and most likely included. Depends if you are used to screens and got used to that or if its your first time you can just use byobu and go with the newer more full featured option. You can also use byobu with screen by typing 'byobu-select-backend' and choosing screen if installed.
One cool thing about byobu is that it can start automatically whenever you login to ssh, which can be super useful (you don't have to remember). Just login to the server via ssh then type 'byobu-enable' and logout. When you next login byobu is auto started. Now you can always get your shell back in a disconnection event.
With byobu just logging back in reconnects (if auto start enabled) you to he last session automatically (even from console) so no commands needed to retrieve it but you can also select a session if there were multiple with the byobu-select-session command. It also lets you do silly things like split the screen and wotnot but we don't really talk about it.