Screen Section

A “screen” represents the binding of a graphics device (Device section) and a monitor (Monitor section).

The Default Depth specifies which color depth the server should use by default. The -depth command line option can be used to override this. If neither is specified, the default depth is driver-specific, but in most cases is 8.. 24 should be maximum for most graphics devices.

Each Screen section may have multiple Display subsections and they are optional. You can set different modes and options for displaying device if you want to override the default settings.

Server Section

A “server layout” represents the binding of one or more screens (Screen sections) and one or more input devices (InputDevice sections) to form a complete configuration. If no ServerLayout sections are present, the single active screen and two active (core) input devices are selected as described in the relevant sections above.

Other Options Section

The DRI section (optional) is used to provide some information for the Direct Rendering Infrastructure. In simple terms, the DRI enables hardware-accelerated 3D graphics on Linux. More specifically, it’s a software architecture for coordinating the Linux kernel, X window system, 3D graphics hardware and an OpenGL-based rendering engine.

The Extensions section is used to specify which X11 protocol extensions should be enabled or disabled. The Extensions section is optional, as are all of the entries that may be specified in it.

The Module section is used to specify which Xorg server modules should be loaded. This section is ignored when the Xorg server is built in static form. The type of modules normally loaded in this section are Xorg server extension modules. Most other module types are loaded automatically when they are needed via other mechanisms. The Module section is optional, as are all of the entries that may be specified in it.

The Files section is used to specify some path names required by the server, and is an optional entry.

Saving settings

After you entered your configuration data, before you save them, you have the option to test the x-server hitting the F7 key. If no errors present a message will be displayed saying that the configured server works well and you can see a log file that contains the result of the tested parameters. Seeing that message you can assume that you’ve entered valid values accepted by the x-server, but, too see if you entered the right values for your hardware configuration you have to restart the x-server (the simplest way, reboot the system).

Before you make any changes to your configuration xorg.conf file, located in /etc/X11/ directory, make a backup copy of it, to restore the settings if something goes wrong and your system will be unusable. Also, BE SURE that YOU KNOW EXACTLY what you are doing.

References:

xorg.conf – Configuration File for Xorg X server
Building DRI
Introduction to DRI