XF86Config - Part II

We’re diving into a discussion this week of the XF86Config file. As noted yesterday, there are graphical and text-based tools available in the various Linux distributions to configure your X Window system, but none is as accurate or flexible as manually editing the XF86Config file. It’s a mystery to many new Linux users that’s relatively easy to solve if you know what you’re looking at and for.

Most distributions have moved to XF86Config-4, the configuration file for version 4 of XFree86. Because the basic concepts of XF86Config still apply in XF86Config-4, the first chunk of our discussion will be centered on the older style XF86Config file. Toward the end of this series, we’ll move to XF86Config-4, focusing on both the similarities and differences with the older style configuration file.

At first glance, the XF86Config file can be a daunting mish-mash of references to monitors, pointers and screens. Like any well-written configuration file, though, there is a clear logic to its layout. Today, we’ll take a quick spin through the major sections of XF86Config, providing a brief description of the function of each.

The XF86Config file normally consists of 8 sections, each related to a different element of your X Window system. When you consider the tasks necessary to draw windows, track user interaction and utilize that interaction in program execution, these sections begin to make some sense. They cover all the bases for these discrete tasks, tying them together to create an end result of graphically-based functionality. Here, in brief, is a look at the sections of the XF86Config file that help to achieve that goal.

• Files
  The files section contains the configuration details for font paths and RGB (Red, Green, Blue) color transitions. This section commonly contains subsections for the RGBPath, FontPath and ModulePath. In other words, the Files section of the XF86Config file contains a roadmap to other color-, font- and module-specific files.
• Modules
  The Modules section specifies which loadable modules will be used by the X server. Modules to interact with such devices as touchpads and joysticks will be referenced in this section.
• ServerFlags
  The ServerFlags section defines a set of X server behaviours that are triggered by user actions or internal signals. ServerFlags is, in essence, an interpreter. It both defines the signals the X server should watch for and sets the response of the server in the event these signals are received.
• Keyboard
  The Keyboard section contains all the information necessary for the X server to handle input from the keyboard. These parameters may include flags (as with the ServerFlags section), protocols and key mappings. It can also contain rules that combine protocols, mappings and actions into a single block of code.
• Pointers
  The Pointers section contains the configuration for the mouse on your X Window system. Like the Keyboard section, the Pointers section provides information to the X Window server on the type of mouse, button mappings, actions, protocols, and necessary device files to operate your mouse.
• Monitor
  The Monitor section, for obvious reasons, is crucial in the configuration of your X Window setup. By defining horizontal and vertical refresh rates, gamma values and operating modes, the Monitor section of XF86Config determines what, if anything, you’ll see as visual feedback to your actions. This is a crucial section of XF86Config for another reason, as well. The monitor is, perhaps, the most delicate link in the X Window chain of hardware. Such actions as setting refresh rates higher than your monitor is capable of handling can cause serious damage. For that reason, editing the Monitor section of the XF86Config file should be done with great caution.
• Device
  The Device section contains all the necessary settings for your video card. Chipset, dotclocks and video RAM are all defined in the Device section, along with other optional video parameters.
• Screens
  The Screen section is where much of the other information provided in XF86Config starts to come together. A single screen subsection defines the combination of devices, monitor, video modes, pointer, and keyboard for your system. In many ways, the elements of XF86Config prior to the Screens section merely define and direct the elements of X Window. It’s in the Screens section that the user pulls these various elements together to create a single set of optimal configurations for their system.

These are the basic elements of the XF86Config file for your Linux system. Many of the individual sub-sections are defined by default at installation and may or may not be commented out (utilizing the # sign at the beginning of a line of code) in your particular file. And, as I’ve already mentioned, these are the basic sections for earlier versions of XF86Config. Even though XF86Config-4 has greatly simplified the manual configuration process, it’s important to understand some of the ancestry of the current system.

Tomorrow, we’ll look at subsections - sections within the sections - and comment both on their purpose and on the value of clean coding when making modifications.