While there is rarely a need to manually edit the /etc/X11/xorg.conf file, it is useful to understand
the various sections and optional parameters available, especially
when troubleshooting.
The /etc/X11/xorg.conf file is
comprised of many different sections which address specific aspects
of the system hardware.
Each section begins with a Section
"<section-name>" line
(where <section-name> is the
title for the section) and ends with an EndSection line. Within each of the sections are
lines containing option names and at least one option value,
sometimes surrounded with double quotes (").
Lines beginning with a hash mark (#)
are not read by the X server and are used for human-readable
comments.
Some options within the /etc/X11/xorg.conf file accept a boolean switch
which turns the feature on or off. Acceptable boolean values
are:
-
1, on,
true, or yes
— Turns the option on.
-
0, off,
false, or no
— Turns the option off.
The following are some of the more important sections in the
order in which they appear in a typical /etc/X11/xorg.conf file. More detailed information
about the X server configuration file can be found in the
xorg.conf man page.
The optional ServerFlags section
contains miscellaneous global X server settings. Any settings in
this section may be overridden by options placed in the ServerLayout section (refer to
Section 7.3.1.3 ServerLayout
for details).
Each entry within the ServerFlags
section is on its own line and begins with the term Option followed by an option enclosed in double
quotation marks (").
The following is a sample ServerFlags
section:
Section "ServerFlags"
Option "DontZap" "true"
EndSection
|
The following lists some of the most useful options:
-
"DontZap" "<boolean>" — When the value of
<boolean> is set to true, this
setting prevents the use of the [Ctrl]-[Alt]-[Backspace] key
combination to immediately terminate the X server.
-
"DontZoom" "<boolean>" — When the value of
<boolean> is set to true, this
setting prevents cycling through configured video resolutions using
the [Ctrl]-[Alt]-[Keypad-Plus] and
[Ctrl]-[Alt]-[Keypad-Minus]
key combinations.
The ServerLayout section binds together
the input and output devices controlled by the X server. At a
minimum, this section must specify one output device and at least
two input devices (a keyboard and a mouse).
The following example illustrates a typical ServerLayout section:
Section "ServerLayout"
Identifier "Default Layout"
Screen 0 "Screen0" 0 0
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
EndSection
|
The following entries are commonly used in the ServerLayout section:
-
Identifier — Specifies a unique
name for this ServerLayout section.
-
Screen — Specifies the name of a
Screen section to be used with the X
server. More than one Screen option may be
present.
The following is an example of a typical Screen entry:
The first number in this example Screen
entry (0) indicates that the first monitor
connector or head on the video card uses
the configuration specified in the Screen
section with the identifier "Screen0".
If the video card has more than one head, another Screen entry would be necessary with a different
number and a different Screen section
identifier.
The numbers to the right of "Screen0"
give the X and Y absolute coordinates for the upper-left corner of
the screen (0 0 by default).
-
InputDevice — Specifies the name
of an InputDevice section to be used with
the X server.
There must be at least two InputDevice
entries: one for the default mouse and one for the default
keyboard. The options CorePointer and
CoreKeyboard indicate that these are the
primary mouse and keyboard.
-
Option "<option-name>" — An optional
entry which specifies extra parameters for the section. Any options
listed here override those listed in the ServerFlags section.
Replace <option-name> with
a valid option listed for this section in the xorg.conf man page.
It is possible to create more than one ServerLayout section. However, the server only reads
the first one to appear unless an alternate ServerLayout section is specified as a command line
argument.
The Files section sets paths for
services vital to the X server, such as the font path.
The following example illustrates a typical Files section:
Section "Files"
RgbPath "/usr/X11R6/lib/X11/rgb"
FontPath "unix/:7100"
EndSection
|
The following entries are commonly used in the Files section:
-
RgbPath — Specifies the location
of the RGB color database. This database defines all valid color
names in X and ties them to specific RGB values.
-
FontPath — Specifies where the X
server must connect to obtain fonts from the xfs font server.
By default, the FontPath is unix/:7100. This tells the X server to obtain font
information using UNIX-domain sockets for inter-process
communication (IPC) on port 7100.
Refer to Section 7.4 Fonts
for more information concerning X and fonts.
-
ModulePath — An optional
parameter which specifies alternate directories which store X
server modules.
The Module section specifies which
modules from the /usr/X11R6/lib/modules/
directory the X server is to load. Modules add additional
functionality to the X server.
The following example illustrates a typical Module section:
Section "Module"
Load "dbe"
Load "extmod"
Load "fbdevhw"
Load "glx"
Load "record"
Load "freetype"
Load "type1"
Load "dri"
EndSection
|
Each InputDevice section configures one
input device for the X server. Systems typically have at least two
InputDevice sections, keyboard and
mouse.
The following example illustrates a typical InputDevice section for a mouse:
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mice"
Option "Emulate3Buttons" "no"
EndSection
|
The following entries are commonly used in the InputDevice section:
-
Identifier — Specifies a unique
name for this InputDevice section. This is
a required entry.
-
Driver — Specifies the name of
the device driver X must load for the device.
-
Option — Specifies necessary
options pertaining to the device.
For a mouse, these options typically include:
-
Protocol — Specifies the protocol
used by the mouse, such as IMPS/2.
-
Device — Specifies the location
of the physical device.
-
Emulate3Buttons — Specifies
whether to allow a two button mouse to act like a three button
mouse when both mouse buttons are pressed simultaneously.
Consult the xorg.conf man page for a
list of valid options for this section.
By default, the InputDevice section has
comments to allow users to configure additional options.
Each Monitor section configures one
type of monitor used by the system. While one Monitor section is the minimum, additional instances
may occur for each monitor type in use with the machine.
The best way to configure a monitor is to configure X during the
installation process or by using the X
Configuration Tool. For more about using the X Configuration Tool, refer to the chapter titled
X Window System Configuration in the
Red Hat Enterprise Linux System Administration
Guide.
This example illustrates a typical Monitor section for a monitor:
Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "DDC Probed Monitor - ViewSonic G773-2"
DisplaySize 320 240
HorizSync 30.0 - 70.0
VertRefresh 50.0 - 180.0
EndSection
|
 |
Warning |
| |
Be careful if manually editing values in the Monitor section of /etc/X11/xorg.conf. Inappropriate values can damage
or destroy a monitor. Consult the monitor's documentation for a
listing of safe operating parameters.
|
The following are commonly entries used in the Monitor section:
-
Identifier — Specifies a unique
name for this Monitor section. This is a
required entry.
-
VendorName — An optional
parameter which specifies the vendor of the monitor.
-
ModelName — An optional parameter
which specifies the monitor's model name.
-
DisplaySize — An optional
parameter which specifies, in millimeters, the physical size of the
monitor's picture area.
-
HorizSync — Specifies the range
of horizontal sync frequencies compatible with the monitor in kHz.
These values help the X server determine the validity of built in
or specified Modeline entries for the
monitor.
-
VertRefresh — Specifies the range
of vertical refresh frequencies supported by the monitor, in kHz.
These values help the X server determine the validity of built in
or specified Modeline entries for the
monitor.
-
Modeline — An optional parameter
which specifies additional video modes for the monitor at
particular resolutions, with certain horizontal sync and vertical
refresh resolutions. Refer to the xorg.conf man page for a more detailed explanation
of Modeline entries.
-
Option "<option-name>" — An optional
entry which specifies extra parameters for the section. Replace
<option-name> with a valid
option listed for this section in the xorg.conf man page.
Each Device section configures one
video card on the system. While one Device
section is the minimum, additional instances may occur for each
video card installed on the machine.
The best way to configure a video card is to configure X during
the installation process or by using the X
Configuration Tool. For more about using the X Configuration Tool, refer to the chapter titled
X Window System Configuration in the
Red Hat Enterprise Linux System Administration
Guide.
The following example illustrates a typical Device section for a video card:
Section "Device"
Identifier "Videocard0"
Driver "mga"
VendorName "Videocard vendor"
BoardName "Matrox Millennium G200"
VideoRam 8192
Option "dpms"
EndSection
|
The following entries are commonly used in the Device section:
-
Identifier — Specifies a unique
name for this Device section. This is a
required entry.
-
Driver — Specifies which driver
the X server must load to utilize the video card. A list of drivers
can be found in /usr/X11R6/lib/X11/Cards,
which is installed with the hwdata
package.
-
VendorName — An optional
parameter which specifies the vendor of the video card.
-
BoardName — An optional parameter
which specifies the name of the video card.
-
VideoRam — An optional parameter
which specifies the amount of RAM available on the video card in
kilobytes. This setting is only necessary for video cards the X
server cannot probe to detect the amount of video RAM.
-
BusID — An optional entry which
specifies the bus location of the video card. This option is only
mandatory for systems with multiple cards.
-
Screen — An optional entry which
specifies which monitor connector or head on the video card the
Device section configures. This option is
only useful for video cards with multiple heads.
If multiple monitors are connected to different heads on the
same video card, separate Device sections
must exist and each of these sections must have a different
Screen value.
Values for the Screen entry must be an
integer. The first head on the video card has a value of 0. The value for each additional head increments
this value by one.
-
Option "<option-name>" — An optional
entry which specifies extra parameters for the section. Replace
<option-name> with a valid
option listed for this section in the xorg.conf man page.
One of the more common options is "dpms", which activates the Service Star energy
compliance setting for the monitor.
Each Screen section binds one video
card (or video card head) to one monitor by referencing the
Device section and the Monitor section for each. While one Screen section is the minimum, additional instances
may occur for each video card and monitor combination present on
the machine.
The following example illustrates a typical Screen section:
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 16
SubSection "Display"
Depth 24
Modes "1280x1024" "1280x960" "1152x864" "1024x768" "800x600" "640x480"
EndSubSection
SubSection "Display"
Depth 16
Modes "1152x864" "1024x768" "800x600" "640x480"
EndSubSection
EndSection
|
The following entries are commonly used in the Screen section:
-
Identifier — Specifies a unique
name for this Screen section. This is a
required entry.
-
Device — Specifies the unique
name of a Device section. This is a
required entry.
-
Monitor — Specifies the unique
name of a Monitor section. This is a
required entry.
-
DefaultDepth — Specifies the
default color depth in bits. In the previous example, 16, which provides thousands of colors, is the
default. Multiple DefaultDepth entries are
permitted, but at least one is required.
-
SubSection "Display" — Specifies
the screen modes available at a particular color depth. A
Screen section may have multiple
Display subsections, but at least one is
required for the color depth specified in the DefaultDepth entry.
-
Option "<option-name>" — An optional
entry which specifies extra parameters for the section. Replace
<option-name> with a valid
option listed for this section in the xorg.conf man page.
The optional DRI section specifies
parameters for the Direct Rendering
Infrastructure (DRI). DRI is an
interface which allows 3D software applications to take advantage
of 3D hardware acceleration capabilities built into most modern
video hardware. In addition, DRI can improve 2D performance via
hardware acceleration, if supported by the video card driver.
This section is ignored unless DRI is enabled in the Module section.
The following example illustrates a typical DRI section:
Section "DRI"
Group 0
Mode 0666
EndSection
|
Since different video cards use DRI in different ways, do not
alter the values for this section without first referring to
https://dri.sourceforge.net/.
