Troubleshooting Your Desktop

If your desktop is not functioning properly (or at all) it may be that your video card was not configured properly. This section helps you get your video card configured properly and your desktop up and running smoothly.

GUI doesn't Work at Start-Up

If Fedora or RHEL has been successfully installed (along with the desired desktop environment) but the GUI wasn't set to start at boot time, you may only see a simple text-based login prompt when you start Fedora or RHEL. This login prompt may look something like this:

 Fedora Core release 6 Kernel 2.6.17 on an i686 YourComputer login: 

Log in as the root user . As noted earlier, you can check if you have a GUI that is at least working well enough for you to correct it. Type the following command:

 #  startx  

If the desktop works fine when you type startx , you might want to change to a graphical login, so the GUI starts automatically every time. See the "What Happens During Desktop Startup" sidebar for information on booting to a GUI. If X crashes, see /var/log/Xorg.0.log for clues about what went wrong.

If your GUI is so distorted you can't even see to correct it, switch to a virtual terminal to correct the problem. For example, hold the Ctrl and Alt keys, and press F2. You will see a plain text login prompt. Log in as root user and type init 3 to make the garbled GUI login screen go away. As an alternative, type Ctrl+Alt+Backspace to close the X session. Then you can try tuning your video card as described in the following section.

Tip 

Switching virtual terminals is a great way to get out of a GUI that is broken or stuck and run the commands you need to fix a problem. You can use any function key from F1 through F8 with Ctrl+Alt to switch terminals. The GUI itself is probably on the F7 virtual terminal. Linux experts use virtual terminals during Fedora or RHEL installation to debug a problem or during startup to view text startup messages.

What Happens During Desktop Startup?

The X server and graphical login screen is started by the prefdm script. By default, the login screen is displayed by the GNOME display manager ( gdm command), which handles both logging in and starting the desktop environment for your console monitor, as well as graphical logins from other computers and X terminals. (If you don't like the way the login screen appears, run gdmsetup as root user. It will let you change the login greeter screen or even allow no-password logins.)

The prefdm script is launched only if the run level in the /etc/inittab file is set to 5 , as follows :

 id:5:initdefault: 

If the initdefault state is 3 , the system boots to a text-based login prompt. See Chapter 12 for information on Linux run states and start-up processes.

Some processes started during every X session are launched from scripts in the /etc/X11/xinit/xinitrc.d directory. Check those scripts to see if any of the settings they include might be causing problems. (You can also use those scripts to launch applications of your own each time X starts.)

If you are unable to get the video card and monitor configured properly, or if you don't need a GUI, you can configure the computer to start up in text mode. To do this using any shell text editor (such as the vi command described in Chapter 4), change the initdefault line in the /etc/inittab file from id:5:initdefault: to id:3:initdefault .

If you prefer to have Fedora or RHEL boot to a GUI, change the 3 to a 5.

Tuning Your Video Card and Monitor

If your GUI is starting up but needs some tuning (to get better resolution, more colors, or to fix flickering ), you can use the Display Settings window to fix your desktop. For the current Fedora and RHEL versions, the Display Settings window was enhanced so that you can use it from a command with no GUI running. The next sections describe how to run the Display Settings window, then how to review the resulting xorg.conf file to understand your settings.

Running the Display Settings Window

The Fedora Project recently replaced the Xconfigurator tool with a new Display Settings window ( system-config-display command). This window lets you set the most basic functions relating to your display, monitor, and video card. The Display Settings window is easy-to-use and no longer requires a running X desktop to use it.

To open the Display Settings window from the Desktop menu, click System Settings Display. To open that window from a text prompt (even with no GUI running), type system-config-display (as root).

From the Settings tab of the Display Settings window, you can try different resolutions (screen width and height in pixels) and color depth (from 256 colors to millions of color ). Click the Hardware tab to try to configure your monitor and video card. Click the Dual head tab if you have a video card that supports two monitors that you can use side-by-side with Fedora or RHEL. Click OK to save your changes.

Here are a few tips for using the Display Settings window:

• If you know your monitor type, but it is not being detected , click the Hardware tab and then click Configure. You can select the monitor from a list of monitors (by manufacturer) or, if it's not on the list, enter information about the monitor's horizontal and vertical sync rates from the manufacturer's instructions.

• If you don't know the vertical and horizontal sync rates, you can choose a generic monitor from the list. You could simply choose a generic CRT or Generic LCD at a resolution you would expect the monitor to support.

Changes made in the Display Settings window result in the creation of a new /etc/X11/xorg.conf file. The next section describes what the xorg.conf file contains.

Tip 

If the Display Settings window fails to create a working xorg.conf file, you can try another approach. With no GUI on as root user, type the following commands from a shell:

  # Xorg -configure   # X -xf86config /root/xorg.conf.new  

The first line creates xorg.conf.new in the /root directory. The second tries to start your GUI with that new config file. You should see the mouse cursor (an X) and a blank screen. If the GUI works, type Ctrl-Alt-Backspace to exit, and then copy /root/xorg.conf.new to /etc/X11/xorg.conf . You may need to run system-config-mouse to get the mouse working properly after this.

Understanding the xorg.conf File

Beginning with Fedora Core 2, the XFree86 X server was replaced by the X server from X.Org. Although that change should be invisible to most users, if you like to change X settings directly, you need to know that the main X configuration file is now /etc/X11/xorg.conf and not /etc/X11/XF86Config .

The xorg.conf file (located in the /etc/X11 directory) contains definitions used by the X server to use your video card, keyboard, mouse, and monitor. In general, novice users should not edit this file directly. For some video cards, however, manual configuration may be required to get the card working properly.

The following is a description of the basic information contained in the xorg.conf file:

• ServerLayout section - Binds input and output devices for your X session. Lets you set server definitions for different X servers (if necessary).

• Module section - Describes which X server modules should be loaded.

• Files section - Sets the locations of the RGB (color), modules, and fonts databases.

• InputDevice sections - Separate sections identify keyboard and mouse input devices.

• Monitor section - Sets the type of monitor, along with its horizontal sync rate, vertical refresh rate, and settings needed to operate at different resolutions.

• Device section - Identifies your video card and, optionally , video RAM and clock information for the chipset.

• Screen section - Binds the graphics board and monitor information to be referenced later by the ServerLayout section.

• Keyboard section - Sets keyboard settings, including the layout of the keyboard and the way certain key sequences are mapped to the keyboard.

• Pointer section - Selects the pointer you are using (typically a mouse linked to /dev/mouse ). Also sets speed and button emulation, when appropriate.

• DRI - Provides information for Direct Rendering Infrastructure (used for accelerated 3D graphics).

Configuring Video Cards for Gaming

Some games and video players require special features to work properly (or at all, in some cases). For games that require 3D hardware acceleration, including some that run under TransGaming's WineX, TransGaming recommends using NVIDIA GeForce Graphics cards.

Because only basic NVIDIA video card drivers are included in Fedora (NVIDIA's own drivers are not open source), you need to get NVIDIA drivers yourself to use those cards for gaming. You can get Linux NVIDIA drivers from www.nvidia.com/object/linux.html or you can install them from the rpm.livna.org Fedora repository.

Caution 

Because some components of the video drivers from NVIDIA can conflict with those that come with Fedora or RHEL. See the section on choosing a video card for gaming in Chapter 7 for further information on getting and using NVIDIA drivers in Fedora.Games that don't require 3D hardware acceleration should work fine with most video cards that are supported by the X.Org X server drivers.

Tip 

To use hardware DRI acceleration on Voodoo 3 cards, you must have your display set to use 16bpp resolution. On Voodoo 5 cards, only 16bpp and 24bpp resolutions are supported. Voodoo chipsets and other 3DFX technology is now owned by NVIDIA.

Getting More Information

If you tried configuring X and you still have a server that crashes or has a garbled display, your video card may either be unsupported or may require special configuration. Here are several locations you can check for further information:

• X.Org ( www.x.org ) - The latest information about the X servers that come with Fedora and RHEL is available from the X.Org Web site. X.Org is the freeware version of X recently used by many major Linux distributions to replace the XFree86 X server.

• X documentation - README files that are specific to different types of video cards are delivered with the X.Org X server. Visit the X doc directory (/usr/X11R6/lib/X11/doc ) for a README file specific to the type of video card (or more specifically , the video chipset) you are using. A lot of good information can also be found on the xorg.conf man page (type man xorg.conf).