Chapter 10. Installing the X
Window System
We come now to the X Window System--one of the most powerful and
important software packages available for Linux. If you've ever used
X on a Unix system before, you're in luck; running
X under Linux is almost no different from Unix systems.
And, if you've never had the occasion to use it before, never fear:
salvation is at hand.
It's difficult to describe the X Window System in a nutshell.
X is a complete windowing graphics interface for
Unix systems. It provides a huge number of options to both the programmer
and the user. For instance, there are at least half a dozen
window managers available for X, each one offering a different
interface for manipulating windows. By customizing the attributes of
the window manager, you have complete control over how windows are
placed on the screen, the colors and borders used to decorate them, and
so forth.
X was originally developed by Project Athena at MIT and Digital
Equipment Corporation. The current version
of X is Version 11 revision 6 (X11R6), which
was first released in April 1994. Since the release of Version 11, X has
virtually taken over as the de facto standard for Unix graphical environments.
It is now developed and distributed by The Open Group, an association
that is composed of many large computer manufacturers.
Despite its commercial use, the X Window System remains distributable under a
liberal license from the X Consortium. As such, a complete
implementation of X is freely available for Linux systems. XFree86, an
implementation of X, originally for i386 Unix
systems, is the version most often used by Linux. Today, this version
supports not only Intel-based systems, but also Alpha
AXP, MicroSPARC, PowerPC, and other
architectures. Further architectures will follow. XFree86 is based on
X386-1.2, which was part of the official X11R5 sources, but is no longer
maintained and is therefore outdated. The current
versions now have only a very little part in common with their
ancestors. Support for innumerable graphics boards and many other
operating systems (including Linux) has been added--and XFree86
implements the latest version X11R6.3.
In
this chapter, we
will tell you how to install and configure the X Window System,
and in the next chapter, we will explore how to use X.
Linux distributions automatically install X (if you ask them
to). If you're lucky, you won't need this chapter at all. But
a large percentage of users aren't lucky--the distribution
doesn't recognize some graphics hardware, writes a file to
the wrong location so the X server can't start up, or has some
other problem. One of the big advantages of this book is that
we take you down to the depths of X configuration so you can
get it running no matter what your distribution does. You may
not need to read this chapter, but if you do need it, you'll
appreciate everything that's here.
10.1. X Concepts
X is based on a client-server model in which the X server is a
program that runs on your system and handles all access to the graphics
hardware. An X client is an applications program that communicates
with the server, sending it requests such as "draw a line" or
"pay attention to keyboard input." The X server takes care of
servicing these requests by drawing a line on the display or sending
user input (via the keyboard, mouse, or whatever) to the client application.
Examples of X clients are xterm (which emulates a terminal within
a window) or xman (an X-based manual-page reader).
It is important to note that X is a network-oriented graphics system.
That is, X clients can run either locally (on the same system that the
server is running) or remotely (on a system somewhere on a TCP/IP network).
The X server listens to both local and remote network sockets for
requests from clients. This feature is obviously quite powerful.
If you have a connection to a TCP/IP network, you can log in
to another system over
the network and run an X application there, directing it to display on your
local X server.
Further advantages of X are security (if the user so
desires), the modular separation of functions, and
the support for many different architectures. All this makes the
X Window System technically superior by far to all other
window systems.
The X Window System makes a distinction between application behavior
and window management.
Clients running under X are displayed within one or more windows
on your screen. However, how windows are manipulated (placed on the display,
resized, and so forth) and how they are decorated (the appearance of
the window frames) is not controlled by the X server. Instead, it is
handled by another X client called a window manager that runs
concurrently with the other X clients.
Your choice of window manager
will decide to some extent how X as a whole looks and feels. Most
window managers are utterly flexible and configurable; the user can
select the look of the window decoration, the focus policy, the meaning
of the mouse buttons when the mouse is on the background part of the screen rather than on an application window, and many other things by editing the configuration files of the
window manager. More modern systems even let you configure those
aspects over a graphical user interface.
In order to fully understand the concept of window
managers, you need to know that the window manager does not
affect the presentation of the window created by the client. The
window manager is only in charge of painting the window
decoration, that is, the frame and the buttons that let you close,
move, and resize
windows.
There can be only one window manager on any X
server. Theoretically, it is even possible to completely do away
with window managers, but then you would not be able to move
windows around the screen; put a hidden window on top; or
minimize, maximize, or resize windows
unless the programs themselves
provide this functionality.
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