Section 16.7. Running into Trouble

Often, something will not be quite right when you initially fire up the X server. This is almost always caused by a problem in your file. Usually, the monitor timing values are off or the video card dot clocks are set incorrectly. If your display seems to roll or the edges are fuzzy, this is a clear indication that the monitor timing values or dot clocks are wrong. Also be sure you are correctly specifying your video card chipset, as well as other options for the Device section of These days, there is only one server binary, which loads the module needed for the graphics card in question. The module that loads depends on your Device settings.

If all else fails, try to start X "bare"; that is, use a command such as:

Xorg > /tmp/x.out 2>&1

You can then kill the X server (using the Ctrl-Alt-Backspace key combination) and examine the contents of /tmp/x.out. The X server reports any warnings or errorsfor example, if your video card doesn't have a dot clock corresponding to a mode supported by your monitor. This output can be very helpful in diagnosing all kinds of problems. Examine it closely if your X server does not start up at all, does not provide the resolutions you wanted, or shows a flaky, snowy, or otherwise insufficient picture. Even if everything works to your satisfaction, you might want to check this file for interesting information that the X server has found out about your hardware. The lines starting with (**) contain data that you provided yourself in the configuration file, whereas lines starting with (--) contain data that the X server has found out itself.

Remember that you can use Ctrl-Alt with the plus or minus keys on the numeric keypad to switch between the video modes listed on the Modes line of the Screen section of If the highest-resolution mode doesn't look right, try switching to lower resolutions. This lets you know, at least, that the configurations for those lower resolutions in your X configuration are working correctly.

Also, check the vertical and horizontal size/hold knobs on your monitor. In many cases it is necessary to adjust these when starting up X. For example, if the display seems to be shifted slightly to one side, you can usually correct this using the monitor controls.

The Usenet newsgroup is devoted to discussions about It might be a good idea to watch that newsgroup for postings relating to your video configuration: you might run across someone with the same problems as your own. If this fails, please contact your Linux distributor; their support staff should be able to help you as well.

Hopefully, X is now running for you. You might now want to go back to Chapter 3 and read about the desktop environments that run on top of it. Although it is still possible to run a quite bare-bones X installation with no desktop environment and just a few terminal windows open, this is hardly why you have gone through the trouble of installing X, and the desktop environments are so flexible these days that you can configure them completely to your taste.

Part I: Enjoying and Being Productive on Linux
Part II: System Administration