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X11 Configuration

Written by IT News on 11:30 PM

Having problem with X11 configuration? here is a short tips how to learn X11 configuration.

Before starting.

Before configuration of X11 the following information about the target system is needed:

  • Monitor specifications
  • Video Adapter chipset
  • Video Adapter memory

The specifications for the monitor are used by X11 to determine the resolution and refresh rate to run at. These specifications can usually be obtained from the documentation that came with the monitor or from the manufacturer's website. There are two ranges of numbers that are needed, the horizontal scan rate and the vertical synchronization rate.

The video adapter's chipset defines what driver module X11 uses to talk to the graphics hardware. With most chipsets, this can be automatically determined, but it is still useful to know in case the automatic detection does not work correctly.

Video memory on the graphic adapter determines the resolution and color depth which the system can run at. This is important to know so the user knows the limitations of the system.

Configuring X11

Configuration of X11 is a multi-step process. The first step is to build an initial configuration file. As the super user, simply run:

# Xorg -configure 

This will generate an X11 configuration skeleton file in the /root directory called (whether you su(1) or do a direct login affects the inherited supervisor $HOME directory variable). The X11 program will attempt to probe the graphics hardware on the system and write a configuration file to load the proper drivers for the detected hardware on the target system.

The next step is to test the existing configuration to verify that Xorg can work with the graphics hardware on the target system. To perform this task, type:

# Xorg -config 

If a black and grey grid and an X mouse cursor appear, the configuration was successful. To exit the test, just press Ctrl+Alt+Backspace simultaneously.

Note: If the mouse does not work, you will need to first configure it before proceeding. See Section 2.10.9 in the FreeBSD install chapter.

Next, tune the configuration file to taste. Open the file in a text editor such as emacs(1) or ee(1). First, add the frequencies for the target system's monitor. These are usually expressed as a horizontal and vertical synchronization rate. These values are added to the file under the "Monitor" section:

Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
HorizSync 30-107
VertRefresh 48-120

The HorizSync and VertRefresh keywords may be missing in the configuration file. If they are, they need to be added, with the correct horizontal synchronization rate placed after the HorizSync keyword and the vertical synchronization rate after the VertRefresh keyword. In the example above the target monitor's rates were entered.

X allows DPMS (Energy Star) features to be used with capable monitors. The xset(1) program controls the time-outs and can force standby, suspend, or off modes. If you wish to enable DPMS features for your monitor, you must add the following line to the monitor section:

        Option       "DPMS"

While the configuration file is still open in an editor, select the default resolution and color depth desired. This is defined in the "Screen" section:

Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
Modes "1024x768"

The DefaultDepth keyword describes the color depth to run at by default. This can be overridden with the -depth command line switch to Xorg(1). The Modes keyword describes the resolution to run at for the given color depth. Note that only VESA standard modes are supported as defined by the target system's graphics hardware. In the example above, the default color depth is twenty-four bits per pixel. At this color depth, the accepted resolution is 1024 by 768 pixels.

Finally, write the configuration file and test it using the test mode given above.

Note: One of the tools available to assist you during troubleshooting process are the X11 log files, which contain information on each device that the X11 server attaches to. Xorg log file names are in the format of /var/log/Xorg.0.log. The exact name of the log can vary from Xorg.0.log to Xorg.8.log and so forth.

If all is well, the configuration file needs to be installed in a common location where Xorg(1) can find it. This is typically /etc/X11/xorg.conf or /usr/local/etc/X11/xorg.conf.

# cp /etc/X11/xorg.conf 

The X11 configuration process is now complete. Xorg may be now started with the startx(1) utility. The X11 server may also be started with the use of xdm(1).

Note: There is also a graphical configuration tool, xorgcfg(1), which comes with the X11 distribution. It allows you to interactively define your configuration by choosing the appropriate drivers and settings. This program can be invoked from the console, by typing the command xorgcfg -textmode. For more details, refer to the xorgcfg(1) manual page.

Alternatively, there is also a tool called xorgconfig(1). This program is a console utility that is less user friendly, but it may work in situations where the other tools do not.

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