Screen for more productivity

Today, majority of people are using Windows but what I’m going to talk about is Screen.

Screen is a GNU utility that allows you to use multiple windows (virtual VT100 terminals) in Unix/Linux. Although, if you have a console access, you could spawn multiple terminals, there are two features I would like to highlight.

First, is the fact that screen stays active, even when SSH session is terminated. All processes initiated will keep running and could be re-attached once SSH connection is re-established. Furthermore, since screen session initiates a separate process rather than login session, it is more resource efficient.

In addition, using Screen, it is possible to share processes between multiple users and/or protect using password. For example, you create a screen session and run a command. Another person would be able to list existing screen sessions (screen –ls) and attach a session to their terminal (screen –r). Of course, that is not very secure, therefore it is possible to protect the screen session using user password.

jmarkh@ubuntu-01:~$ screen -S nmap
[detached]
jmarkh@ubuntu-01:~$ screen -S nessus
[detached]
jmarkh@ubuntu-01:~$ screen -ls
There are screens on:
15833.nessus (10-04-08 10:52:20 AM) (Detached)
15813.nmap (10-04-08 10:52:10 AM) (Detached)
15620.pts-0.ubuntu-01 (10-04-08 10:29:38 AM) (Detached)
3 Sockets in /var/run/screen/S-jmarkh.

Here are some commands/shortcuts that could be used with Screen (note that every screen command begins with Ctrl-a):

Ctrl-a c	Create new window (shell)
Ctrl-a k	Kill the current window
C-a C-x	Lock this terminal.
Ctrl-a w	List all windows (the current window is marked with "*")
Ctrl-a 0-9	Go to a window numbered 0-9
Ctrl-a n	Go to the next window
Ctrl-a Ctrl-a	Toggle between the current and previous window
Ctrl-a [	Start copy mode
Ctrl-a ]	Paste copied text
Ctrl-a ?	Help (display a list of commands)
Ctrl-a Ctrl-\	Quit screen
Ctrl-a D (Shift-d)	Power detach and logout
Ctrl-a d	Detach but keep shell window open

The man pages for screen are quite readable and make a good tutorial.

man screen