The Magic of `screen`

Screen is an awesome little utility that, in my opinion, doesn't get enough use by web developers.

Wikipedia tells us that "GNU Screen is a software application that can be used to multiplex several virtual consoles, allowing a user to access multiple separate terminal sessions inside a single terminal window or remote terminal session. It is useful for dealing with multiple programs from a command line interface, and for separating programs from the Unix shell that started the program".

As anyone who's used SSH over a crummy connection knows, having your session disconnect while you're in the middle of doing something (editing a file in the only editor that matters, running a long-running script, etc.) kind of sucks: your task stops running when your SSH session is disconnected.

Using screen on your remote server helps prevent that problem. As soon as you log in, just run screen and you'll get a new terminal. If you type exit, that screen session will terminate. Here's a basic primer on what you can do with screen:

• screen: start a new screen session
• screen -ls: list all screen session
• screen -r or screen -r [session name]: Re-attach a screen session

While you're in a screen session, you can type Ctrl+a d to detach from the session.

So when you get disconnected from SSH and you're running a screen session, you can reconnect and run screen -ls and you'll get a list of all the currently running screen sessions. The screen session that you got disconnected from will be listed as attached because you didn't properly detach from that session. To reconnect to that session, you'll need to use screen -x to reattach (or, if you have multiple screen sessions that are currently detached, you'll need to use screen -x [session name]).

Another cool thing that this lets you do:

1. Have two people log in to a remote server using the same user account.
2. User 1 starts a screen session.
3. User 2 attaches to that screen session using screen -x [session name]

It's like screen sharing for SSH, and it's a great solution for low-bandwidth connections. Note that both users attached to a common screen session can type things in the terminal, so tread carefully - it can be very easy to make a mistake with TWO people at the wheel.

For more information, man screen.