Hack 16. Switch Users Fast 
It's a personal computer. No, it's
a family computer. No,
it's two . . . two . . . two computers in one!
Picture this. You're working at home on an important
business document when your daughter tells you she needs to use the
computer for a while to do research for a school project. Do you have
to close all your applications and log out for her to do her work?
Nope. The following hack shows you a few ways to let your daughter
log in and work with her own desktop without you having to close your
applications and log out first.
You can get two or more users logged in and running separate
graphical desktops on the same machine in a number of ways. This hack
explores the built-in method.
3.2.1. First, a Lesson on Virtual Terminals
You might recall that people used to attach several text-based
terminals to minicomputers and mainframes so that many users could
access the computer at once. Each person could log in to the computer
and work on his separate text console, because he had his own
text-based terminal connected to the main computer. Linux simulates
that kind of behavior with a single terminal and several virtual
consoles. Most Linux distributions provide six text-based virtual
consoles and usually three virtual consoles for graphical desktops,
although more of both types are possible.
If you have used the graphical interface only on Linux and
you're not familiar with virtual consoles,
here's a quick way to see what
they're all about. Press the key combination
Ctrl-Alt-F1. You should see a text-based screen with a login prompt.
This is virtual console 1. Press the key combination Ctrl-Alt-F2.
This is virtual console 2. You can get back to the graphical desktop
by pressing Ctrl-Alt-F7, because the default virtual console for
graphical desktops is virtual console 7. If you can start up a second
graphical desktop, it will be assigned to the next available virtual
console after the previous graphical desktop, which is virtual
console 8. You can switch to that desktop by pressing Ctrl-Alt-F8.
So, when you achieve your goal of starting up two separate graphical
desktops, you can switch between them by pressing Ctrl-Alt-F7 and
Ctrl-Alt-F8.
3.2.2. The Built-In KDE and GNOME Way
Some Linux distributions
with the latest versions of
GNOME or KDE include a menu option to log in as another user on a
separate virtual terminal. For example, as of this writing, one menu
sequence (on Gentoo Linux) for GNOME is Applications System
ToolsNew Login. This brings up a second GNOME-based
graphical login screen (GDM), from which a second user
can log in and start working with her account. This works only if you
started GNOME from GDM. Here's why: after you start
a GNOME session, part of GDM is still running in the background
waiting for you to exit GNOME. The menu selection depends on this
program to be running in the background, so if you
didn't start GNOME with GDM, it
won't be running and waiting to start another
session.
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Fedora Core 2 currently does not offer the option of starting a new
login, even though it runs GDM by default. You can still get multiple
simultaneous logins with graphical desktops using the other
techniques described in this hack.
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The latest versions of KDE have a similar option. The menu sequence
on my Gentoo system is K MenuSystemNew Login.
(Beware: I take the risk of running the latest unstable versions of
software on my system, so you might not have this option.) Again,
this will work only if you logged in to KDE from the KDE graphical
login screen, KDM. This launches a second KDM graphical login screen,
from which a second user can log in to her own session.
Because your version of GNOME and/or KDE probably lacks these menu
options, here are two additional, easy ways to get two or more
graphical login screens running at once. The first way sets up
multiple login screens for KDM. The second sets up multiple login
screens for GDM.
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