Chapter 6.

The X Window System

While the heart of Red Hat Linux is the kernel, for many users, the face of the operating system is the

graphical environment provided by the X Window System, also called simply X.

This chapter is an introduction to the behind the scenes world of XFree86, the open source imple 

mentation of X provided with Red Hat Linux.

6.1. The Power of X

Linux began as a powerful, server based operating system, excelling at efficiently processing com 

plicated programs requiring high CPU utilization and handling requests from hundreds or thousands

of clients through network connections. However, because of its open nature and stability, Linux has

quickly developed into a popular GUI based operating system for workstations, both in the home or

in the workplace.

In the UNIX  world, windowing environments have existed for decades, predating many of the

current mainstream operating systems. The X Window System is now the dominant graphical user

interface (GUI) for UNIX like operating systems.

To create this GUI for the user, X uses a client server architecture. An X server process is started

and X client processes can connect to it via a network or local loopback interface. The server process

handles the communication with the hardware, such as the video card, monitor, keyboard, and mouse.

The X client exists in the user space, issuing requests to the X server.

On Red Hat Linux systems, the XFree86 server fills the role of the X server. As a large scope open

source software project, with hundreds of developers around the world, XFree86 features rapid devel 

opment, a wide degree of support for various hardware devices and architectures, and the ability to

run on different operating systems and platforms.

Most Red Hat Linux desktop users are unaware of the XFree86 server running on their system. They

are much more concerned with the particular desktop environment in which they spend most of their

time. The Red Hat Linux installation program does an excellent job of configuring your XFree86

server during the installation process, ensuring that X performs optimally when first started.

The X server performs many difficult tasks using a wide array of hardware, requiring detailed config 

uration. If some aspect of your system changes, such as the monitor or video card, XFree86 will need

to be reconfigured. In addition, if you are troubleshooting a problem with XFree86 that cannot be

solved using a configuration utility, such as the X Configuration Tool (

redhat config xfree86

),

you may need to access its configuration file directly.

Tip

X Configuration Tool is capable of configuring XFree86 while the X server is active. To activate the

configuration program from the command line, type redhat config xfree86. To start X Configu 

ration Tool while in an active X session, go to the Main Menu Button (on the Panel) => System

Tools => Display. After using X Configuration Tool during an X session, you will need to log out of

the current X session, then log back in for the changes to take effect.