Andrew Hudson - Fedora™ Unleashed, 2008 edition

The Modulesection of the xorg.conffile specifies loadable modules or drivers to load for the X session. This section might look like this:

Section "Module"

Load "dbe"

Load "extmod"

Load "fbdevhw"

Load "glx"

Load "record"

Load "freetype"

Load "type1"

Load "dri"

EndSection

These modules can range from special video card support to font rasterizers. The modules are located in subdirectories under the /usr/lib/modulesdirectory.

The InputDevicesection configures a specific device, such as a keyboard or mouse, as in this example:

Section "InputDevice"

Identifier "Keyboard0"

Driver "kbd"

Option "XkbModel" "pc105"

Option "XkbLayout" "us"

EndSection

Section "InputDevice"

Identifier "Mouse0" Driver "mouse"

Option "Protocol" "IMPS/2"

Option "Device" "/dev/input/mice"

Option "ZAxisMapping" "4 5"

Option "Emulate3Buttons" "yes"

EndSection

You can configure multiple devices, and there might be multiple InputDevicesections. The preceding example specifies a basic keyboard and a two-button PS/2 mouse (actually, a Dell touchpad pointer). An InputDevicesection that specifies use of a USB device could be used at the same time (to enable mousing with PS/2 and USB pointers) and might look like this:

Section "InputDevice"

Identifier "Mouse0"

Driver "mouse"

Option "Device" "/dev/input/mice"

Option "Protocol" "IMPS/2"

Option "Emulate3Buttons" "off"

Option "ZAxisMapping" "4 5"

EndSection

If you change your computer's pointing device, you should then run Fedora's system-config-mouse client, which automatically updates your system's xorg.conffile.

From Fedora Core 3 onward, the location for the mouse device changed from /dev/mouseto /dev/input/mice. Unfortunately, when system-config-displaywrites the xorg.conffile, it sometimes gets a little confused and still maps the mouse to /dev/mouserather than /dev/input/mice. This is where a little knowledge of vicomes in handy!

The Monitorsection configures the designated display device as declared in the ServerLayoutsection, as shown in this example:

Section "Monitor"

Identifier "Monitor0"

VendorName "Monitor Vendor"

ModelName "Monitor Model"

DisplaySize 300 220

HorizSync 31.5-48.5

VertRefresh 50-70

Option "dpms"

EndSection

Note that the X server automatically determines the best video timings according to the horizontal and vertical sync and refresh values in this section. If required, old-style mode- line entries (used by distributions and servers prior to XFree86 4.0) might still be used. If the monitor is automatically detected when you configure X (see the "Configuring X" section later in this chapter), its definition and capabilities are inserted in your xorg.conffile from the MonitorsDBdatabase. This database contains more than 600 monitors and is located in the /usr/share/hwdatadirectory.

The Devicesection provides details about the video graphics chipset used by the computer, as in this example:

Section "Device"

Identifier "Videocard0"

Driver "radeon"

VendorName "Videocard vendor"

BoardName "ATI Radeon Mobility M6"

EndSection

This example identifies an installed video card as using an ATI Mobility M6 graphics chipset. The Driverentry tells the Xorgserver to load the radeon_drv.omodule from the /usr/lib/modules/driversdirectory. Different chipsets have different options. For example, here's the entry for a NeoMagic video chipset:

Section "Device"

Identifier "NeoMagic (laptop/notebook)"

Driver "neomagic"

VendorName "NeoMagic (laptop/notebook)"

BoardName "NeoMagic (laptop/notebook)"

Option "externDisp"

Option "internDisp"

EndSection

In this example, the Devicesection specifies the driver for the graphics card ( neomagic_drv.o) and enables two chipset options (externDispand internDisp)to allow display on the laptop's LCD screen and an attached monitor.

The Xorgserver supports hundreds of different video chipsets. If you configure X11 but subsequently change the installed video card, you need to edit the existing Devicesection or generate a new xorg.conffile, using one of the X configuration tools discussed in this chapter, to reflect the new card's capabilities. You can find details about options for some chipsets in a companion man page. You should look at these sources for hints about optimizations and troubleshooting.

The Screensection ties together the information from the previous sections (using the Screen0, Device, and Monitor Identifierentries). It can also specify one or more color depths and resolutions for the session. Here's an example:

Section "Screen"

Identifier "Screen0"

Device "Videocard0"

Monitor "Monitor0" DefaultDepth 24

SubSection "Display"

Viewport 0 0 Depth 16

Modes "1024x768" "800x600" "640x480"

EndSubSection

EndSection

In this example, a color depth of thousands of colors and a resolution of 1024×768 is the default, with optional resolutions of 800×600 and 640×480. Multiple Displaysubsection entries with different color depths and resolutions (with settings such as Depth 24for millions of colors) can be used if supported by the graphics card and monitor combination. You can also use a DefaultDepth entry (which is 24, or thousands of colors, in the example), along with a specific color depth to standardize display depths in installations

You can also specify a desktop resolution larger than that supported by the hardware in your monitor or notebook display. This setting is known as a virtual resolution in the Displaysubsection. This allows, for example, an 800×600 display to pan (that is, slide around inside) a virtual window of 1024×768.

If your monitor and graphics card support multiple resolutions and the settings are properly configured, you can use the key combination of Ctrl+Alt+Keypad+ or Ctrl+Alt+Keypad to change resolutions on-the-fly during your X session.

Although the Fedora installer can be used to configure X during installation, problems can arise if the PC's video card is not recognized. If you are unable to configure X during installation (refer to Chapter 1, "Installing Fedora"), do not specify booting to a graphical configuration and skip the X configuration portion of the installation. Note that some installs, such as for servers, don't require that X be configured for use to support active X sessions, but might require installation of X and related software to support remote users and clients.