Tuesday, 22 March 2016

Understanding the X11 configuration

X / X11 is the defacto display server for the vast majority of linux distributions.

There are large selection of window managers available that sit upon X - for example: XFCE, Gnome and KDE to name a few.

There are several main configuration files:

- /etc/X11/xorg.conf.d/* : Contains a group of configuration files (must be .conf) that are parsed as part of / in addition to the xorg.conf file.

- /etc/X11/xorg.conf (sometimes /etc/xorg.conf) : The main configuration file that is read upon starting the X server.

** Note: xorg.conf is not created / needed by default in some distro's - e.g. later versions of Ubuntu.

Defaults and other configuration provided by other vendors can be accessed from /usr/share/X11/xorg.conf.d/*.

In order to generate your xorg.conf file you can use the following command:

Xorg :0 -configure


X -configure

A typical xorg.conf comprises of the following:

- Modules: This section defines the relevant modules that should be loaded in order to run X e.g. glx (which is the module that provides support for OpenGL)

- Extensions: This section defines extensions - simply provide additional functionality to the X system e.g. XEvIE which allows you to intercept mouse and keyboard events.

- Files: This section defines files - such as fonts that are loaded with the X server.

- ServerFlags: This section allows you to modify the behavior of the X server e.g. Option "AutoAddDevices" "false" (which disables device hotplugging.)

- InputDevice: Defines the drivers and configuration for any input devices - mouse, keyboard etc.

- Monitor: This section defines settings such as the monitor frequency - ** Be careful here as tweaking these settings could damage your monitor - refer to your hardware vendor's manual for the relevant settings!

- Device: This is where settings relating to your graphics card are defined e.g. type, video mode etc.

- Screen: This is where settings such as the screen resolution for your monitor(s) is defined.

** Changes you make to xorg.conf should generally (with most ditro's) persist! **


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