Using Screen
Steven G. Isaacson
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Although the user's perspective of modern computing is
usually graphical, much of what systems administrators do is in
character mode, perhaps through an xterm window, a
telnet session, or an actual ASCII terminal attached as the
system console. Often, we dial into the network or a system
configured as a communications server to perform administrative
tasks during what other people consider non-business hours. Such
single-threaded connections, however, leave much to be desired from
a convenience standpoint. One solution to the limitations of such
connections is a utility called "screen."
Screen is a window-managing program that allows you to interact
with one or more programs (usually login shells) from a single
session. You can cut-and-paste between windows, view scroll-back
history, log activity, and lock the screen -- all from a single
telnet or rlogin session. The most remarkable feature
of screen, however, is its ability to detach and reattach
sessions.
Detachment
Detaching a login session is analogous to putting a phone call
on hold, except that you can pick up the call again from any phone
in the world. For example, suppose you're at your desk working
with two telnet windows open. In one window, you're
replying to email and in the other, you're checking the
configuration on some remote system. Then, the phone rings and
you're called to the computer room. In the computer room, you
have to reboot a computer. While it's rebooting, you grab
another terminal, log in, and reattach to your email and remote
configuration telnet sessions.
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