From Linux Man Pages
xorg.conf - Configuration File for Xorg
INTRODUCTION
Xorg supports several mechanisms for supplying/obtaining configuration and run-time parameters: command line
options, environment variables, the xorg.conf configuration file, auto-detection, and fallback defaults. When
the same information is supplied in more than one way, the highest precedence mechanism is used. The list of
mechanisms is ordered from highest precedence to lowest. Note that not all parameters can be supplied via all
methods. The available command line options and environment variables (and some defaults) are described in the
Xserver(1) and Xorg(1) manual pages. Most configuration file parameters, with their defaults, are described
below. Driver and module specific configuration parameters are described in the relevant driver or module manual
page.
DESCRIPTION
Xorg uses a configuration file called xorg.conf for its initial setup. This configuration file is searched for
in the following places when the server is started as a normal user:
/etc/X11/<cmdline>
/usr/etc/X11/<cmdline>
/etc/X11/$XORGCONFIG
/usr/etc/X11/$XORGCONFIG
/etc/X11/xorg.conf-4
/etc/X11/xorg.conf
/etc/xorg.conf
/usr/etc/X11/xorg.conf.<hostname>
/usr/etc/X11/xorg.conf-4
/usr/etc/X11/xorg.conf
/usr/lib/X11/xorg.conf.<hostname>
/usr/lib/X11/xorg.conf-4
/usr/lib/X11/xorg.conf
where <cmdline> is a relative path (with no ".." components) specified with the -config command line option,
$XORGCONFIG is the relative path (with no ".." components) specified by that environment variable, and <hostname>
is the machine's hostname as reported by gethostname(3).
When the Xorg server is started by the "root" user, the config file search locations are as follows:
<cmdline>
/etc/X11/<cmdline>
/usr/etc/X11/<cmdline>
$XORGCONFIG
/etc/X11/$XORGCONFIG
/usr/etc/X11/$XORGCONFIG
/etc/X11/xorg.conf-4
/etc/X11/xorg.conf
/etc/xorg.conf
/usr/etc/X11/xorg.conf.<hostname>
/usr/etc/X11/xorg.conf-4
/usr/etc/X11/xorg.conf
/usr/lib/X11/xorg.conf.<hostname>
/usr/lib/X11/xorg.conf-4
/usr/lib/X11/xorg.conf
where <cmdline> is the path specified with the -config command line option (which may be absolute or relative),
$XORGCONFIG is the path specified by that environment variable (absolute or relative), and <hostname> is the
machine's hostname as reported by gethostname(3).
The xorg.conf file is composed of a number of sections which may be present in any order. Each section has the
form:
Section "SectionName"
SectionEntry
...
EndSection
The section names are:
Files File pathnames
ServerFlags Server flags
Module Dynamic module loading
InputDevice Input device description
Device Graphics device description
VideoAdaptor Xv video adaptor description
Monitor Monitor description
Modes Video modes descriptions
Screen Screen configuration
ServerLayout Overall layout
DRI DRI-specific configuration
Vendor Vendor-specific configuration
The following obsolete section names are still recognised for compatibility purposes. In new config files, the
InputDevice section should be used instead.
Keyboard Keyboard configuration
Pointer Pointer/mouse configuration
The old XInput section is no longer recognised.
The ServerLayout sections are at the highest level. They bind together the input and output devices that will be
used in a session. The input devices are described in the InputDevice sections. Output devices usually consist
of multiple independent components (e.g., a graphics board and a monitor). These multiple components are bound
together in the Screen sections, and it is these that are referenced by the ServerLayout section. Each Screen
section binds together a graphics board and a monitor. The graphics boards are described in the Device sections,
and the monitors are described in the Monitor sections.
Config file keywords are case-insensitive, and "_" characters are ignored. Most strings (including Option names)
are also case-insensitive, and insensitive to white space and "_" characters.
Each config file entry usually takes up a single line in the file. They consist of a keyword, which is possibly
followed by one or more arguments, with the number and types of the arguments depending on the keyword. The
argument types are:
Integer an integer number in decimal, hex or octal
Real a floating point number
String a string enclosed in double quote marks (")
Note: hex integer values must be prefixed with "0x", and octal values with "0".
A special keyword called Option may be used to provide free-form data to various components of the server. The
Option keyword takes either one or two string arguments. The first is the option name, and the optional second
argument is the option value. Some commonly used option value types include:
Integer an integer number in decimal, hex or octal
Real a floating point number
String a sequence of characters
Boolean a boolean value (see below)
Frequency a frequency value (see below)
Note that all Option values, not just strings, must be enclosed in quotes.
Boolean options may optionally have a value specified. When no value is specified, the option's value is TRUE.
The following boolean option values are recognised as TRUE:
1, on, true, yes
and the following boolean option values are recognised as FALSE:
0, off, false, no
If an option name is prefixed with "No", then the option value is negated.
Example: the following option entries are equivalent:
Option "Accel" "Off"
Option "NoAccel"
Option "NoAccel" "On"
Option "Accel" "false"
Option "Accel" "no"
Frequency option values consist of a real number that is optionally followed by one of the following frequency
units:
Hz, k, kHz, M, MHz
When the unit name is omitted, the correct units will be determined from the value and the expectations of the
appropriate range of the value. It is recommended that the units always be specified when using frequency option
values to avoid any errors in determining the value.
FILES SECTION
The Files section is used to specify some path names required by the server. Some of these paths can also be set
from the command line (see Xserver(1) and Xorg(1)). The command line settings override the values specified in
the config file. The Files section is optional, as are all of the entries that may appear in it.
The entries that can appear in this section are:
FontPath "path"
sets the search path for fonts. This path is a comma separated list of font path elements which the Xorg
server searches for font databases. Multiple FontPath entries may be specified, and they will be concate-
nated to build up the fontpath used by the server. Font path elements may be either absolute directory
paths, or a font server identifier. Font server identifiers have the form:
<trans>/<hostname>:<port-number>
where <trans> is the transport type to use to connect to the font server (e.g., unix for UNIX-domain sock-
ets or tcp for a TCP/IP connection), <hostname> is the hostname of the machine running the font server,
and <port-number> is the port number that the font server is listening on (usually 7100).
When this entry is not specified in the config file, the server falls back to the compiled-in default font
path, which contains the following font path elements:
/usr/lib/X11/fonts/misc/
/usr/lib/X11/fonts/TTF/
/usr/lib/X11/fonts/Type1/
/usr/lib/X11/fonts/CID/
/usr/lib/X11/fonts/75dpi/
/usr/lib/X11/fonts/100dpi/
The recommended font path contains the following font path elements:
/usr/lib/X11/fonts/local/
/usr/lib/X11/fonts/misc/
/usr/lib/X11/fonts/75dpi/:unscaled
/usr/lib/X11/fonts/100dpi/:unscaled
/usr/lib/X11/fonts/Type1/
/usr/lib/X11/fonts/CID/
/usr/lib/X11/fonts/Speedo/
/usr/lib/X11/fonts/75dpi/
/usr/lib/X11/fonts/100dpi/
Font path elements that are found to be invalid are removed from the font path when the server starts up.
RGBPath "path"
sets the path name for the RGB color database. When this entry is not specified in the config file, the
server falls back to the compiled-in default RGB path, which is:
/usr/share/X11/rgb
Note that an implicit .txt is added to this path if the server was compiled to use text rather than binary format
RGB color databases.
ModulePath "path"
sets the search path for loadable Xorg server modules. This path is a comma separated list of directories
which the Xorg server searches for loadable modules loading in the order specified. Multiple ModulePath
entries may be specified, and they will be concatenated to build the module search path used by the
server.
SERVERFLAGS SECTION
In addition to options specific to this section (described below), the ServerFlags section is used to specify
some global Xorg server options. All of the entries in this section are Options, although for compatibility pur-
poses some of the old style entries are still recognised. Those old style entries are not documented here, and
using them is discouraged. The ServerFlags section is optional, as are the entries that may be specified in it.
Options specified in this section (with the exception of the "DefaultServerLayout" Option) may be overridden by
Options specified in the active ServerLayout section. Options with command line equivalents are overridden when
their command line equivalent is used. The options recognised by this section are:
Option "DefaultServerLayout" "layout-id"
This specifies the default ServerLayout section to use in the absence of the -layout command line option.
Option "NoTrapSignals" "boolean"
This prevents the Xorg server from trapping a range of unexpected fatal signals and exiting cleanly.
Instead, the Xorg server will die and drop core where the fault occurred. The default behaviour is for
the Xorg server to exit cleanly, but still drop a core file. In general you never want to use this option
unless you are debugging an Xorg server problem and know how to deal with the consequences.
Option "DontVTSwitch" "boolean"
This disallows the use of the Ctrl+Alt+Fn sequence (where Fn refers to one of the numbered function keys).
That sequence is normally used to switch to another "virtual terminal" on operating systems that have this
feature. When this option is enabled, that key sequence has no special meaning and is passed to clients.
Default: off.
Option "DontZap" "boolean"
This disallows the use of the Ctrl+Alt+Backspace sequence. That sequence is normally used to terminate
the Xorg server. When this option is enabled, that key sequence has no special meaning and is passed to
clients. Default: off.
Option "DontZoom" "boolean"
This disallows the use of the Ctrl+Alt+Keypad-Plus and Ctrl+Alt+Keypad-Minus sequences. These sequences
allows you to switch between video modes. When this option is enabled, those key sequences have no spe-
cial meaning and are passed to clients. Default: off.
Option "DisableVidModeExtension" "boolean"
This disables the parts of the VidMode extension used by the xvidtune client that can be used to change
the video modes. Default: the VidMode extension is enabled.
Option "AllowNonLocalXvidtune" "boolean"
This allows the xvidtune client (and other clients that use the VidMode extension) to connect from another
host. Default: off.
Option "DisableModInDev" "boolean"
This disables the parts of the Xorg-Misc extension that can be used to modify the input device settings
dynamically. Default: that functionality is enabled.
Option "AllowNonLocalModInDev" "boolean"
This allows a client to connect from another host and change keyboard and mouse settings in the running
server. Default: off.
Option "AllowMouseOpenFail" "boolean"
This allows the server to start up even if the mouse device can't be opened/initialised. Default: false.
Option "VTInit" "command"
Runs command after the VT used by the server has been opened. The command string is passed to "/bin/sh
-c", and is run with the real user's id with stdin and stdout set to the VT. The purpose of this option
is to allow system dependent VT initialisation commands to be run. This option should rarely be needed.
Default: not set.
Option "VTSysReq" "boolean"
enables the SYSV-style VT switch sequence for non-SYSV systems which support VT switching. This sequence
is Alt-SysRq followed by a function key (Fn). This prevents the Xorg server trapping the keys used for
the default VT switch sequence, which means that clients can access them. Default: off.
Option "XkbDisable" "boolean"
disable/enable the XKEYBOARD extension. The -kb command line option overrides this config file option.
Default: XKB is enabled.
Option "BlankTime" "time"
sets the inactivity timeout for the blanking phase of the screensaver. time is in minutes. This is
equivalent to the Xorg server's `-s' flag, and the value can be changed at run-time with xset(1).
Default: 10 minutes.
Option "StandbyTime" "time"
sets the inactivity timeout for the "standby" phase of DPMS mode. time is in minutes, and the value can
be changed at run-time with xset(1). Default: 20 minutes. This is only suitable for VESA DPMS compatible
monitors, and may not be supported by all video drivers. It is only enabled for screens that have the
"DPMS" option set (see the MONITOR section below).
Option "SuspendTime" "time"
sets the inactivity timeout for the "suspend" phase of DPMS mode. time is in minutes, and the value can
be changed at run-time with xset(1). Default: 30 minutes. This is only suitable for VESA DPMS compatible
monitors, and may not be supported by all video drivers. It is only enabled for screens that have the
"DPMS" option set (see the MONITOR section below).
Option "OffTime" "time"
sets the inactivity timeout for the "off" phase of DPMS mode. time is in minutes, and the value can be
changed at run-time with xset(1). Default: 40 minutes. This is only suitable for VESA DPMS compatible
monitors, and may not be supported by all video drivers. It is only enabled for screens that have the
"DPMS" option set (see the MONITOR section below).
Option "Pixmap" "bpp"
This sets the pixmap format to use for depth 24. Allowed values for bpp are 24 and 32. Default: 32
unless driver constraints don't allow this (which is rare). Note: some clients don't behave well when
this value is set to 24.
Option "PC98" "boolean"
Specify that the machine is a Japanese PC-98 machine. This should not be enabled for anything other than
the Japanese-specific PC-98 architecture. Default: auto-detected.
Option "NoPM" "boolean"
Disables something to do with power management events. Default: PM enabled on platforms that support it.
Option "Xinerama" "boolean"
enable or disable XINERAMA extension. Default is disabled.
Option "AllowDeactivateGrabs" "boolean"
This option enables the use of the Ctrl+Alt+Keypad-Divide key sequence to deactivate any active keyboard
and mouse grabs. Default: off.
Option "AllowClosedownGrabs" "boolean"
This option enables the use of the Ctrl+Alt+Keypad-Multiply key sequence to kill clients with an active
keyboard or mouse grab as well as killing any application that may have locked the server, normally using
the XGrabServer(3) Xlib function. Default: off.
Note that the options AllowDeactivateGrabs and AllowClosedownGrabs will allow users to remove the grab
used by screen saver/locker programs. An API was written to such cases. If you enable this option, make
sure your screen saver/locker is updated.
Option "HandleSpecialKeys" "when"
This option controls when the server uses the builtin handler to process special key combinations (such as
Ctrl+Alt+Backspace). Normally the XKEYBOARD extension keymaps will provide mappings for each of the
special key combinations, so the builtin handler is not needed unless the XKEYBOARD extension is disabled.
The value of when can be Always, Never, or WhenNeeded. Default: Use the builtin handler only if needed.
The server will scan the keymap for a mapping to the Terminate action and, if found, use XKEYBOARD for
processing actions, otherwise the builtin handler will be used.
Option "AIGLX" "boolean"
enable or disable AIGLX. AIGLX is enabled by default.
Option "IgnoreABI" "boolean"
Allow modules built for a different, potentially incompatible version of the X server to load. Disabled by
default.
MODULE SECTION
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 types of modules normally loaded in this section are Xorg server
extension modules, and font rasteriser 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.
Entries in this section may be in two forms. The first and most commonly used form is an entry that uses the
Load keyword, as described here:
Load "modulename"
This instructs the server to load the module called modulename. The module name given should be the mod-
ule's standard name, not the module file name. The standard name is case-sensitive, and does not include
the "lib" prefix, or the ".a", ".o", or ".so" suffixes.
Example: the Type 1 font rasteriser can be loaded with the following entry:
Load "type1"
The second form of entry is a SubSection, with the subsection name being the module name, and the contents of the
SubSection being Options that are passed to the module when it is loaded.
Example: the extmod module (which contains a miscellaneous group of server extensions) can be loaded, with the
Xorg-DGA extension disabled by using the following entry:
SubSection "extmod"
Option "omit XFree86-DGA"
EndSubSection
Modules are searched for in each directory specified in the ModulePath search path, and in the drivers, input,
extensions, fonts, and internal subdirectories of each of those directories. In addition to this, operating sys-
tem specific subdirectories of all the above are searched first if they exist.
To see what font and extension modules are available, check the contents of the following directories:
/usr/lib/modules/fonts
/usr/lib/modules/extensions
The "bitmap" font modules is loaded automatically. It is recommended that at very least the "extmod" extension
module be loaded. If it isn't some commonly used server extensions (like the SHAPE extension) will not be avail-
able.
INPUTDEVICE SECTION
The config file may have multiple InputDevice sections. There will normally be at least two: one for the core
(primary) keyboard, and one of the core pointer. If either of these two is missing, a default configuration for
the missing ones will be used. Currently the default configuration may not work as expected on all platforms.
InputDevice sections have the following format:
Section "InputDevice"
Identifier "name"
Driver "inputdriver"
options
...
EndSection
The Identifier and Driver entries are required in all InputDevice sections. All other entries are optional.
The Identifier entry specifies the unique name for this input device. The Driver entry specifies the name of the
driver to use for this input device. When using the loadable server, the input driver module "inputdriver" will
be loaded for each active InputDevice section. An InputDevice section is considered active if it is referenced
by an active ServerLayout section, if it is referenced by the -keyboard or -pointer command line options, or if
it is selected implicitly as the core pointer or keyboard device in the absence of such explicit references. The
most commonly used input drivers are "keyboard" and "mouse".
In the absence of an explicitly specified core input device, the first InputDevice marked as CorePointer (or
CoreKeyboard) is used. If there is no match there, the first InputDevice that uses the "mouse" (or "keyboard" or
"kbd") driver is used. The final fallback is to use built-in default configurations.
InputDevice sections recognise some driver-independent Options, which are described here. See the individual
input driver manual pages for a description of the device-specific options.
Option "CorePointer"
When this is set, the input device is installed as the core (primary) pointer device. There must be
exactly one core pointer. If this option is not set here, or in the ServerLayout section, or from the
-pointer command line option, then the first input device that is capable of being used as a core pointer
will be selected as the core pointer. This option is implicitly set when the obsolete Pointer section is
used.
Option "CoreKeyboard"
When this is set, the input device is to be installed as the core (primary) keyboard device. There must
be exactly one core keyboard. If this option is not set here, in the ServerLayout section, or from the
-keyboard command line option, then the first input device that is capable of being used as a core key-
board will be selected as the core keyboard. This option is implicitly set when the obsolete Keyboard
section is used.
Option "AlwaysCore" "boolean"
Option "SendCoreEvents" "boolean"
Both of these options are equivalent, and when enabled cause the input device to always report core
events. This can be used, for example, to allow an additional pointer device to generate core pointer
events (like moving the cursor, etc).
Option "HistorySize" "number"
Sets the motion history size. Default: 0.
Option "SendDragEvents" "boolean"
???
DEVICE SECTION
The config file may have multiple Device sections. There must be at least one, for the video card being used.
Device sections have the following format:
Section "Device"
Identifier "name"
Driver "driver"
entries
...
EndSection
The Identifier and Driver entries are required in all Device sections. All other entries are optional.
The Identifier entry specifies the unique name for this graphics device. The Driver entry specifies the name of
the driver to use for this graphics device. When using the loadable server, the driver module "driver" will be
loaded for each active Device section. A Device section is considered active if it is referenced by an active
Screen section.
Device sections recognise some driver-independent entries and Options, which are described here. Not all drivers
make use of these driver-independent entries, and many of those that do don't require them to be specified
because the information is auto-detected. See the individual graphics driver manual pages for further informa-
tion about this, and for a description of the device-specific options. Note that most of the Options listed here
(but not the other entries) may be specified in the Screen section instead of here in the Device section.
BusID "bus-id"
This specifies the bus location of the graphics card. For PCI/AGP cards, the bus-id string has the form
PCI:bus:device:function (e.g., "PCI:1:0:0" might be appropriate for an AGP card). This field is usually
optional in single-head configurations when using the primary graphics card. In multi-head configura-
tions, or when using a secondary graphics card in a single-head configuration, this entry is mandatory.
Its main purpose is to make an unambiguous connection between the device section and the hardware it is
representing. This information can usually be found by running the Xorg server with the -scanpci command
line option.
Screen number
This option is mandatory for cards where a single PCI entity can drive more than one display (i.e., multi-
ple CRTCs sharing a single graphics accelerator and video memory). One Device section is required for
each head, and this parameter determines which head each of the Device sections applies to. The legal
values of number range from 0 to one less than the total number of heads per entity. Most drivers require
that the primary screen(0) be present.
Chipset "chipset"
This usually optional entry specifies the chipset used on the graphics board. In most cases this entry is
not required because the drivers will probe the hardware to determine the chipset type. Don't specify it
unless the driver-specific documentation recommends that you do.
Ramdac "ramdac-type"
This optional entry specifies the type of RAMDAC used on the graphics board. This is only used by a few
of the drivers, and in most cases it is not required because the drivers will probe the hardware to deter-
mine the RAMDAC type where possible. Don't specify it unless the driver-specific documentation recommends
that you do.
DacSpeed speed
DacSpeed speed-8 speed-16 speed-24 speed-32
This optional entry specifies the RAMDAC speed rating (which is usually printed on the RAMDAC chip). The
speed is in MHz. When one value is given, it applies to all framebuffer pixel sizes. When multiple val-
ues are give, they apply to the framebuffer pixel sizes 8, 16, 24 and 32 respectively. This is not used
by many drivers, and only needs to be specified when the speed rating of the RAMDAC is different from the
defaults built in to driver, or when the driver can't auto-detect the correct defaults. Don't specify it
unless the driver-specific documentation recommends that you do.
Clocks clock ...
specifies the pixel that are on your graphics board. The clocks are in MHz, and may be specified as a
floating point number. The value is stored internally to the nearest kHz. The ordering of the clocks is
important. It must match the order in which they are selected on the graphics board. Multiple Clocks
lines may be specified, and each is concatenated to form the list. Most drivers do not use this entry,
and it is only required for some older boards with non-programmable clocks. Don't specify this entry
unless the driver-specific documentation explicitly recommends that you do.
ClockChip "clockchip-type"
This optional entry is used to specify the clock chip type on graphics boards which have a programmable
clock generator. Only a few Xorg drivers support programmable clock chips. For details, see the appro-
priate driver manual page.
VideoRam mem
This optional entry specifies the amount of video ram that is installed on the graphics board. This is
measured in kBytes. In most cases this is not required because the Xorg server probes the graphics board
to determine this quantity. The driver-specific documentation should indicate when it might be needed.
BiosBase baseaddress
This optional entry specifies the base address of the video BIOS for the VGA board. This address is nor-
mally auto-detected, and should only be specified if the driver-specific documentation recommends it.
MemBase baseaddress
This optional entry specifies the memory base address of a graphics board's linear frame buffer. This
entry is not used by many drivers, and it should only be specified if the driver-specific documentation
recommends it.
IOBase baseaddress
This optional entry specifies the IO base address. This entry is not used by many drivers, and it should
only be specified if the driver-specific documentation recommends it.
ChipID id
This optional entry specifies a numerical ID representing the chip type. For PCI cards, it is usually the
device ID. This can be used to override the auto-detection, but that should only be done when the driver-
specific documentation recommends it.
ChipRev rev
This optional entry specifies the chip revision number. This can be used to override the auto-detection,
but that should only be done when the driver-specific documentation recommends it.
TextClockFreq freq
This optional entry specifies the pixel clock frequency that is used for the regular text mode. The fre-
quency is specified in MHz. This is rarely used.
Options
Option flags may be specified in the Device sections. These include driver-specific options and driver-
independent options. The former are described in the driver-specific documentation. Some of the latter
are described below in the section about the Screen section, and they may also be included here.
VIDEOADAPTOR SECTION
Nobody wants to say how this works. Maybe nobody knows ...
MONITOR SECTION
The config file may have multiple Monitor sections. There should normally be at least one, for the monitor being
used, but a default configuration will be created when one isn't specified.
Monitor sections have the following format:
Section "Monitor"
Identifier "name"
entries
...
EndSection
The only mandatory entry in a Monitor section is the Identifier entry.
The Identifier entry specifies the unique name for this monitor. The Monitor section provides information about
the specifications of the monitor, monitor-specific Options, and information about the video modes to use with
the monitor. Specifying video modes is optional because the server now has a built-in list of VESA standard
modes. When modes are specified explicitly in the Monitor section (with the Modes, ModeLine, or UseModes key-
words), built-in modes with the same names are not included. Built-in modes with different names are, however,
still implicitly included.
The entries that may be used in Monitor sections are described below.
VendorName "vendor"
This optional entry specifies the monitor's manufacturer.
ModelName "model"
This optional entry specifies the monitor's model.
HorizSync horizsync-range
gives the range(s) of horizontal sync frequencies supported by the monitor. horizsync-range may be a
comma separated list of either discrete values or ranges of values. A range of values is two values sepa-
rated by a dash. By default the values are in units of kHz. They may be specified in MHz or Hz if MHz or
Hz is added to the end of the line. The data given here is used by the Xorg server to determine if video
modes are within the specifications of the monitor. This information should be available in the monitor's
handbook. If this entry is omitted, a default range of 28-33kHz is used.
VertRefresh vertrefresh-range
gives the range(s) of vertical refresh frequencies supported by the monitor. vertrefresh-range may be a
comma separated list of either discrete values or ranges of values. A range of values is two values sepa-
rated by a dash. By default the values are in units of Hz. They may be specified in MHz or kHz if MHz or
kHz is added to the end of the line. The data given here is used by the Xorg server to determine if video
modes are within the specifications of the monitor. This information should be available in the monitor's
handbook. If this entry is omitted, a default range of 43-72Hz is used.
DisplaySize width height
This optional entry gives the width and height, in millimetres, of the picture area of the monitor. If
given this is used to calculate the horizontal and vertical pitch (DPI) of the screen.
Gamma gamma-value
Gamma red-gamma green-gamma blue-gamma
This is an optional entry that can be used to specify the gamma correction for the monitor. It may be
specified as either a single value or as three separate RGB values. The values should be in the range 0.1
to 10.0, and the default is 1.0. Not all drivers are capable of using this information.
UseModes "modesection-id"
Include the set of modes listed in the Modes section called modesection-id. This make all of the modes
defined in that section available for use by this monitor.
Mode "name"
This is an optional multi-line entry that can be used to provide definitions for video modes for the moni-
tor. In most cases this isn't necessary because the built-in set of VESA standard modes will be suffi-
cient. The Mode keyword indicates the start of a multi-line video mode description. The mode description
is terminated with the EndMode keyword. The mode description consists of the following entries:
DotClock clock
is the dot (pixel) clock rate to be used for the mode.
HTimings hdisp hsyncstart hsyncend htotal
specifies the horizontal timings for the mode.
VTimings vdisp vsyncstart vsyncend vtotal
specifies the vertical timings for the mode.
Flags "flag" ...
specifies an optional set of mode flags, each of which is a separate string in double quotes. "Inter-
lace" indicates that the mode is interlaced. "DoubleScan" indicates a mode where each scanline is
doubled. "+HSync" and "-HSync" can be used to select the polarity of the HSync signal. "+VSync" and
"-VSync" can be used to select the polarity of the VSync signal. "Composite" can be used to specify
composite sync on hardware where this is supported. Additionally, on some hardware, "+CSync" and
"-CSync" may be used to select the composite sync polarity.
HSkew hskew
specifies the number of pixels (towards the right edge of the screen) by which the display enable sig-
nal is to be skewed. Not all drivers use this information. This option might become necessary to
override the default value supplied by the server (if any). "Roving" horizontal lines indicate this
value needs to be increased. If the last few pixels on a scan line appear on the left of the screen,
this value should be decreased.
VScan vscan
specifies the number of times each scanline is painted on the screen. Not all drivers use this infor-
mation. Values less than 1 are treated as 1, which is the default. Generally, the "DoubleScan" Flag
mentioned above doubles this value.
ModeLine "name" mode-description
This entry is a more compact version of the Mode entry, and it also can be used to specify video modes for
the monitor. is a single line format for specifying video modes. In most cases this isn't necessary
because the built-in set of VESA standard modes will be sufficient.
The mode-description is in four sections, the first three of which are mandatory. The first is the dot
(pixel) clock. This is a single number specifying the pixel clock rate for the mode in MHz. The second
section is a list of four numbers specifying the horizontal timings. These numbers are the hdisp, hsync-
start, hsyncend, and htotal values. The third section is a list of four numbers specifying the vertical
timings. These numbers are the vdisp, vsyncstart, vsyncend, and vtotal values. The final section is a
list of flags specifying other characteristics of the mode. Interlace indicates that the mode is inter-
laced. DoubleScan indicates a mode where each scanline is doubled. +HSync and -HSync can be used to
select the polarity of the HSync signal. +VSync and -VSync can be used to select the polarity of the
VSync signal. Composite can be used to specify composite sync on hardware where this is supported. Addi-
tionally, on some hardware, +CSync and -CSync may be used to select the composite sync polarity. The
HSkew and VScan options mentioned above in the Modes entry description can also be used here.
Option "DPMS" "bool"
This option controls whether the server should enable the DPMS extension for power management for this
screen. The default is to enable the extension.
Option "SyncOnGreen" "bool"
This option controls whether the video card should drive the sync signal on the green color pin. Not all
cards support this option, and most monitors do not require it. The default is off.
Option "TargetRefresh" "rate"
This optional entry specifies the vertical refresh rate that the server should aim for when selecting
video modes. Without this option, the default is to prefer modes with higher refresh rates.
MODES SECTION
The config file may have multiple Modes sections, or none. These sections provide a way of defining sets of
video modes independently of the Monitor sections. Monitor sections may include the definitions provided in
these sections by using the UseModes keyword. In most cases the Modes sections are not necessary because the
built-in set of VESA standard modes will be sufficient.
Modes sections have the following format:
Section "Modes"
Identifier "name"
entries
...
EndSection
The Identifier entry specifies the unique name for this set of mode descriptions. The other entries permitted in
Modes sections are the Mode and ModeLine entries that are described above in the Monitor section.
SCREEN SECTION
The config file may have multiple Screen sections. There must be at least one, for the "screen" being used. A
"screen" represents the binding of a graphics device (Device section) and a monitor (Monitor section). A Screen
section is considered "active" if it is referenced by an active ServerLayout section or by the -screen command
line option. If neither of those is present, the first Screen section found in the config file is considered the
active one.
Screen sections have the following format:
Section "Screen"
Identifier "name"
Device "devid"
Monitor "monid"
entries
...
SubSection "Display"
entries
...
EndSubSection
...
EndSection
The Identifier and Device entries are mandatory. All others are optional.
The Identifier entry specifies the unique name for this screen. The Screen section provides information specific
to the whole screen, including screen-specific Options. In multi-head configurations, there will be multiple
active Screen sections, one for each head. The entries available for this section are:
Device "device-id"
This mandatory entry specifies the Device section to be used for this screen. This is what ties a spe-
cific graphics card to a screen. The device-id must match the Identifier of a Device section in the con-
fig file.
Monitor "monitor-id"
specifies which monitor description is to be used for this screen. If a Monitor name is not specified, a
default configuration is used. Currently the default configuration may not function as expected on all
platforms.
VideoAdaptor "xv-id"
specifies an optional Xv video adaptor description to be used with this screen.
DefaultDepth 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.
DefaultFbBpp bpp
specifies which framebuffer layout to use by default. The -fbbpp command line option can be used to over-
ride this. In most cases the driver will chose the best default value for this. The only case where
there is even a choice in this value is for depth 24, where some hardware supports both a packed 24 bit
framebuffer layout and a sparse 32 bit framebuffer layout.
Options
Various Option flags may be specified in the Screen section. Some are driver-specific and are described
in the driver documentation. Others are driver-independent, and will eventually be described here.
Option "Accel"
Enables XAA (X Acceleration Architecture), a mechanism that makes video cards' 2D hardware acceleration
available to the Xorg server. This option is on by default, but it may be necessary to turn it off if
there are bugs in the driver. There are many options to disable specific accelerated operations, listed
below. Note that disabling an operation will have no effect if the operation is not accelerated (whether
due to lack of support in the hardware or in the driver).
Option "BiosLocation" "address"
Set the location of the BIOS for the Int10 module. One may select a BIOS of another card for posting or
the legacy V_BIOS range located at 0xc0000 or an alternative address (BUS_ISA). This is only useful under
very special circumstances and should be used with extreme care.
Option "InitPrimary" "boolean"
Use the Int10 module to initialize the primary graphics card. Normally, only secondary cards are soft-
booted using the Int10 module, as the primary card has already been initialized by the BIOS at boot time.
Default: false.
Option "NoInt10" "boolean"
Disables the Int10 module, a module that uses the int10 call to the BIOS of the graphics card to initial-
ize it. Default: false.
Option "NoMTRR"
Disables MTRR (Memory Type Range Register) support, a feature of modern processors which can improve video
performance by a factor of up to 2.5. Some hardware has buggy MTRR support, and some video drivers have
been known to exhibit problems when MTRR's are used.
Option "XaaNoCPUToScreenColorExpandFill"
Disables accelerated rectangular expansion blits from source patterns stored in system memory (using a
memory-mapped aperture).
Option "XaaNoColor8x8PatternFillRect"
Disables accelerated fills of a rectangular region with a full-color pattern.
Option "XaaNoColor8x8PatternFillTrap"
Disables accelerated fills of a trapezoidal region with a full-color pattern.
Option "XaaNoDashedBresenhamLine"
Disables accelerated dashed Bresenham line draws.
Option "XaaNoDashedTwoPointLine"
Disables accelerated dashed line draws between two arbitrary points.
Option "XaaNoImageWriteRect"
Disables accelerated transfers of full-color rectangular patterns from system memory to video memory
(using a memory-mapped aperture).
Option "XaaNoMono8x8PatternFillRect"
Disables accelerated fills of a rectangular region with a monochrome pattern.
Option "XaaNoMono8x8PatternFillTrap"
Disables accelerated fills of a trapezoidal region with a monochrome pattern.
Option "XaaNoOffscreenPixmaps"
Disables accelerated draws into pixmaps stored in offscreen video memory.
Option "XaaNoPixmapCache"
Disables caching of patterns in offscreen video memory.
Option "XaaNoScanlineCPUToScreenColorExpandFill"
Disables accelerated rectangular expansion blits from source patterns stored in system memory (one scan
line at a time).
Option "XaaNoScanlineImageWriteRect"
Disables accelerated transfers of full-color rectangular patterns from system memory to video memory (one
scan line at a time).
Option "XaaNoScreenToScreenColorExpandFill"
Disables accelerated rectangular expansion blits from source patterns stored in offscreen video memory.
Option "XaaNoScreenToScreenCopy"
Disables accelerated copies of rectangular regions from one part of video memory to another part of video
memory.
Option "XaaNoSolidBresenhamLine"
Disables accelerated solid Bresenham line draws.
Option "XaaNoSolidFillRect"
Disables accelerated solid-color fills of rectangles.
Option "XaaNoSolidFillTrap"
Disables accelerated solid-color fills of Bresenham trapezoids.
Option "XaaNoSolidHorVertLine"
Disables accelerated solid horizontal and vertical line draws.
Option "XaaNoSolidTwoPointLine"
Disables accelerated solid line draws between two arbitrary points.
Each Screen section may optionally contain one or more Display subsections. Those subsections provide
depth/fbbpp specific configuration information, and the one chosen depends on the depth and/or fbbpp that is
being used for the screen. The Display subsection format is described in the section below.
DISPLAY SUBSECTION
Each Screen section may have multiple Display subsections. The "active" Display subsection is the first that
matches the depth and/or fbbpp values being used, or failing that, the first that has neither a depth or fbbpp
value specified. The Display subsections are optional. When there isn't one that matches the depth and/or fbbpp
values being used, all the parameters that can be specified here fall back to their defaults.
Display subsections have the following format:
SubSection "Display"
Depth depth
entries
...
EndSubSection
Depth depth
This entry specifies what colour depth the Display subsection is to be used for. This entry is usually
specified, but it may be omitted to create a match-all Display subsection or when wishing to match only
against the FbBpp parameter. The range of depth values that are allowed depends on the driver. Most
driver support 8, 15, 16 and 24. Some also support 1 and/or 4, and some may support other values (like
30). Note: depth means the number of bits in a pixel that are actually used to determine the pixel
colour. 32 is not a valid depth value. Most hardware that uses 32 bits per pixel only uses 24 of them to
hold the colour information, which means that the colour depth is 24, not 32.
FbBpp bpp
This entry specifies the framebuffer format this Display subsection is to be used for. This entry is only
needed when providing depth 24 configurations that allow a choice between a 24 bpp packed framebuffer for-
mat and a 32bpp sparse framebuffer format. In most cases this entry should not be used.
Weight red-weight green-weight blue-weight
This optional entry specifies the relative RGB weighting to be used for a screen is being used at depth 16
for drivers that allow multiple formats. This may also be specified from the command line with the
-weight option (see Xorg(1)).
Virtual xdim ydim
This optional entry specifies the virtual screen resolution to be used. xdim must be a multiple of either
8 or 16 for most drivers, and a multiple of 32 when running in monochrome mode. The given value will be
rounded down if this is not the case. Video modes which are too large for the specified virtual size will
be rejected. If this entry is not present, the virtual screen resolution will be set to accommodate all
the valid video modes given in the Modes entry. Some drivers/hardware combinations do not support virtual
screens. Refer to the appropriate driver-specific documentation for details.
ViewPort x0 y0
This optional entry sets the upper left corner of the initial display. This is only relevant when the
virtual screen resolution is different from the resolution of the initial video mode. If this entry is
not given, then the initial display will be centered in the virtual display area.
Modes "mode-name" ...
This optional entry specifies the list of video modes to use. Each mode-name specified must be in double
quotes. They must correspond to those specified or referenced in the appropriate Monitor section (includ-
ing implicitly referenced built-in VESA standard modes). The server will delete modes from this list
which don't satisfy various requirements. The first valid mode in this list will be the default display
mode for startup. The list of valid modes is converted internally into a circular list. It is possible
to switch to the next mode with Ctrl+Alt+Keypad-Plus and to the previous mode with Ctrl+Alt+Keypad-Minus.
When this entry is omitted, the valid modes referenced by the appropriate Monitor section will be used.
If the Monitor section contains no modes, then the selection will be taken from the built-in VESA standard
modes.
Visual "visual-name"
This optional entry sets the default root visual type. This may also be specified from the command line
(see the Xserver(1) man page). The visual types available for depth 8 are (default is PseudoColor):
StaticGray
GrayScale
StaticColor
PseudoColor
TrueColor
DirectColor
The visual type available for the depths 15, 16 and 24 are (default is TrueColor):
TrueColor
DirectColor
Not all drivers support DirectColor at these depths.
The visual types available for the depth 4 are (default is StaticColor):
StaticGray
GrayScale
StaticColor
PseudoColor
The visual type available for the depth 1 (monochrome) is StaticGray.
Black red green blue
This optional entry allows the "black" colour to be specified. This is only supported at depth 1. The
default is black.
White red green blue
This optional entry allows the "white" colour to be specified. This is only supported at depth 1. The
default is white.
Options
Option flags may be specified in the Display subsections. These may include driver-specific options and
driver-independent options. The former are described in the driver-specific documentation. Some of the
latter are described above in the section about the Screen section, and they may also be included here.
SERVERLAYOUT SECTION
The config file may have multiple ServerLayout sections. 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.
In multi-head configurations, it also specifies the relative layout of the heads. A ServerLayout section is con-
sidered "active" if it is referenced by the -layout command line option or by an Option "DefaultServerLayout"
entry in the ServerFlags section (the former takes precedence over the latter). If those options are not used,
the first ServerLayout section found in the config file is considered the active one. If no ServerLayout sec-
tions are present, the single active screen and two active (core) input devices are selected as described in the
relevant sections above.
ServerLayout sections have the following format:
Section "ServerLayout"
Identifier "name"
Screen "screen-id"
...
InputDevice "idev-id"
...
options
...
EndSection
Each ServerLayout section must have an Identifier entry and at least one Screen entry.
The Identifier entry specifies the unique name for this server layout. The ServerLayout section provides infor-
mation specific to the whole session, including session-specific Options. The ServerFlags options (described
above) may be specified here, and ones given here override those given in the ServerFlags section.
The entries that may be used in this section are described here.
Screen screen-num "screen-id" position-information
One of these entries must be given for each screen being used in a session. The screen-id field is manda-
tory, and specifies the Screen section being referenced. The screen-num field is optional, and may be
used to specify the screen number in multi-head configurations. When this field is omitted, the screens
will be numbered in the order that they are listed in. The numbering starts from 0, and must be consecu-
tive. The position-information field describes the way multiple screens are positioned. There are a num-
ber of different ways that this information can be provided:
x y
Absolute x y
These both specify that the upper left corner's coordinates are (x,y). The Absolute keyword is
optional. Some older versions of Xorg (4.2 and earlier) don't recognise the Absolute keyword, so it's
safest to just specify the coordinates without it.
RightOf "screen-id"
LeftOf "screen-id"
Above "screen-id"
Below "screen-id"
Relative "screen-id" x y
These give the screen's location relative to another screen. The first four position the screen imme-
diately to the right, left, above or below the other screen. When positioning to the right or left,
the top edges are aligned. When positioning above or below, the left edges are aligned. The Relative
form specifies the offset of the screen's origin (upper left corner) relative to the origin of another
screen.
InputDevice "idev-id" "option" ...
One of these entries should be given for each input device being used in a session. Normally at least two
are required, one each for the core pointer and keyboard devices. If either of those is missing, suitable
InputDevice entries are searched for using the method described above in the INPUTDEVICE section. The
idev-id field is mandatory, and specifies the name of the InputDevice section being referenced. Multiple
option fields may be specified, each in double quotes. The options permitted here are any that may also
be given in the InputDevice sections. Normally only session-specific input device options would be used
here. The most commonly used options are:
"CorePointer"
"CoreKeyboard"
"SendCoreEvents"
and the first two should normally be used to indicate the core pointer and core keyboard devices respec-
tively.
Options
In addition to the following, any option permitted in the ServerFlags section may also be specified here.
When the same option appears in both places, the value given here overrides the one given in the Server-
Flags section.
Option "IsolateDevice" "bus-id"
Restrict device resets to the specified bus-id. See the BusID option (described in DEVICE SECTION, above)
for the format of the bus-id parameter. This option overrides SingleCard, if specified. At present, only
PCI devices can be isolated in this manner.
Option "SingleCard" "boolean"
As IsolateDevice, except that the bus ID of the first device in the layout is used.
Here is an example of a ServerLayout section for a dual headed configuration with two mice:
Section "ServerLayout"
Identifier "Layout 1"
Screen "MGA 1"
Screen "MGA 2" RightOf "MGA 1"
InputDevice "Keyboard 1" "CoreKeyboard"
InputDevice "Mouse 1" "CorePointer"
InputDevice "Mouse 2" "SendCoreEvents"
Option "BlankTime" "5"
EndSection
DRI SECTION
This optional section is used to provide some information for the Direct Rendering Infrastructure. Details about
the format of this section can be found on-line at <http://dri.freedesktop.org/>.
VENDOR SECTION
The optional Vendor section may be used to provide vendor-specific configuration information. Multiple Vendor
sections may be present, and they may contain an Identifier entry and multiple Option flags. The data therein is
not used in this release.
FILES
For an example of an xorg.conf file, see the file installed as /usr/lib/X11/xorg.conf.eg.
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