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/.
