Chapter 35. The X Window System

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While the heart of Red Hat Enterprise 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 X.
Other windowing environments have existed in the UNIX world, including some that predate the release of the X Window System in June 1984. Nonetheless, X has been the default graphical environment for most UNIX-like operating systems, including Red Hat Enterprise Linux, for many years.
The graphical environment for Red Hat Enterprise Linux is supplied by the X.Org Foundation, an open source organization created to manage development and strategy for the X Window System and related technologies. X.Org is a large-scale, rapidly developing project with hundreds of developers around the world. It features a wide degree of support for a variety of hardware devices and architectures, and can run on a variety of different operating systems and platforms. This release for Red Hat Enterprise Linux specifically includes the X11R7.1 release of the X Window System.
The X Window System uses a client-server architecture. The X server (the Xorg binary) listens for connections from X client applications via a network or local loopback interface. The server communicates with the hardware, such as the video card, monitor, keyboard, and mouse. X client applications exist in the user-space, creating a graphical user interface (GUI) for the user and passing user requests to the X server.

35.1. The X11R7.1 Release

Red Hat Enterprise Linux 5.10 now uses the X11R7.1 release as the base X Window System, which includes several video driver, EXA, and platform support enhancements over the previous release, among others. In addition, this release also includes several automatic configuration features for the X server.
X11R7.1 is the first release to take specific advantage of the modularization of the X Window System. This modularization, which splits X into logically distinct modules, makes it easier for open source developers to contribute code to the system.


Red Hat Enterprise Linux no longer provides the XFree86™ server packages. Before upgrading a system to the latest version of Red Hat Enterprise Linux, be sure that the system's video card is compatible with the X11R7.1 release by checking the Red Hat Hardware Compatibility List located online at
In the X11R7.1 release, all libraries, headers, and binaries now live under /usr/ instead of /usr/X11R6. The /etc/X11/ directory contains configuration files for X client and server applications. This includes configuration files for the X server itself, the xfs font server, the X display managers, and many other base components.
The configuration file for the newer Fontconfig-based font architecture is still /etc/fonts/fonts.conf. For more on configuring and adding fonts, refer to Section 35.4, “Fonts”.
Because the X server performs advanced tasks on a wide array of hardware, it requires detailed information about the hardware it works on. The X server automatically detects some of this information; other details must be configured.
The installation program installs and configures X automatically, unless the X11R7.1 release packages are not selected for installation. However, if there are any changes to the monitor, video card or other devices managed by the X server, X must be reconfigured. The best way to do this is to use the X Configuration Tool (system-config-display), particularly for devices that are not detected manually.
In Red Hat Enterprise Linux's default graphical environment, the X Configuration Tool is available at System (on the panel) > Administration > Display.
Changes made with the X Configuration Tool take effect after logging out and logging back in.
For more information about X Configuration Tool, refer to Chapter 36, X Window System Configuration.
In some situations, reconfiguring the X server may require manually editing its configuration file, /etc/X11/xorg.conf. For information about the structure of this file, refer to Section 35.3, “X Server Configuration Files”.
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