First of all, what screen does. You start screen inside a terminal session (local or SSH remote), and then you can create additional sessions though Ctrl-A C. The initial screen is number 0, the next one 1, and so on. You can switch between screens with Ctrl-A # where # is the screen number. This way, you can have multiple things going within a single ssh connection, very handy. But that’s not all!

If you get disconnected (it happens and you reconnect, your screen sessions will still be there, and running too. You can reattach with screen -r. To do a nice disconnect, you can do Ctrl-A D (detach) before closing your ssh connection.

You can also have multiple screen sessions by name, screens within screens (that confuses me for the control keys so I tend not to use that), and an absolute supertrick is that you can actually share a screen session with someone else. That’s sometimes mighty handy with two engineers to look at something, and also for showing things to clients.

The tool itself is absolutely ancient (aka rock solid, in maintenance mode), I did a quick check and I see references as far back as 1987. I remember using it long long ago, might’ve been a XENIX box. I reckon screen’s authors deserve a prize for creating one of the most useful tools ever!

Default Linux installs often don’t have it, but rectifying that is as simple as sudo apt-get install screen or sudo yum install screen. Then, man screen is your friend, but there are also quite a few decent tutorials on the web.