If you want to configure your X Window System, there are three options: Direct configuration of the X Window configuration file, the Red Hat Display Settings tool (system-config-display), or automatic installation and configuration of the X Window during the installation process.
Even if you didn't install any graphics software when you installed RHEL, you can still use the system-config-display command. It starts its own default graphics mode if it detects a graphics driver.
The Red Hat Display Settings tool is a stand-alone program that you can run at any time from the command line. The basic routines that start with the system-config-display command are also used by the Red Hat installation program if you choose to install and configure the X Window System at that time.
The system-config-display program is a character-based menu-driven interface that helps you configure your video hardware. If you're starting from a text console, it automatically probes your video card and selects the appropriate X server image. If system-config-display cannot detect your graphics card, it allows you to select it from the list of supported video cards.
It's easy to start the Red Hat Display Settings tool. Just type system-config-display at a command line interface. It provides a simple GUI, even if you start it from a regular text console. It starts the Display Settings window similar to that shown in Figure 14-7.
Figure 14-7: The Display Settings tool, started from the text console
You can set the default resolution and color depth under the Settings tab. If the Display Settings tool successfully identifies your hardware, you'll see it listed under the Hardware tab. In this case, it detected a VMware graphics driver with a LCD monitor. You can change these settings by clicking the associated button. If your hardware supports it, you can configure:
Monitor resolutions between 640×480 and 1920×1440.
A color depth of thousands or millions of colors. Thousands corresponds to 16-bit color, and millions corresponds to 24- or 32-bit color, depending on the capability of your hardware.
But if you want to select a different hardware component, you can select it from a list. Click the Hardware tab, shown in Figure 14-8.
Figure 14-8: Display settings
You'll see options to configure your monitor and video card. Click the Configure button in the Video Card section. This should bring up the Video Card dialog box shown in Figure 14-9.
Figure 14-9: Selecting a graphics card
Browse through the list of video cards. If you do not see your graphics card here, it may not be supported. In this case, there are several options:
Select a video card at least similar to your model. Alternatively, you may find a generic server such as a VESA driver (generic) that is compatible with your video card. Test and if necessary edit the /etc/X11/xorg.conf file to complete your changes.
Check online for other Linux users who are running the X Window System with the same type of hardware. Red Hat maintains mailing lists where many users ask such questions; for the current set of lists, see www.redhat.com/mailman/listinfo.
Use the Unsupported VGA or VESA compatible X Window Server.
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The VESA (Video Electronics Standards Association) driver is also known as SVGA (Super Video Graphics Array).
Go to www.X.org and download the latest drivers. You'll need to edit the /etc/X11/xorg.conf file directly to point to this driver.
Once your selections are complete, click OK. This returns you to the Hardware tab. If your video card is so capable, you'll be able to activate the Enable Hardware 3D Acceleration option. (Otherwise, you won't even see the option in the menu.) Next, configure the Monitor. Click the Configure button in the Monitor Type section of the Hardware tab to open the dialog box shown in Figure 14-10.
Figure 14-10: Selecting a monitor
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Configuring the X Window System to run on a laptop can create challenges. If you are planning to install Red Hat Enterprise Linux on a laptop, a good source for tips and additional information is the Linux on Laptops Web site at www.linux-laptop.net. When all else failed during a recent installation, I was able to run system-config-display remotely, over an SSH connection.
There are a number of ways to configure the X Window with command line tools. If you have problems with the X Window, the first thing to do is check the log file, in /var/log/Xorg.0.log. More information is available in the "Troubleshooting" section later in this chapter.
For a quicker look at the start process, move to runlevel 3 with the init 3 command. Simulate the GUI start process with the following command:
# Xorg -probeonly
Some problems may keep the system-config-display command from working. In that case, you can use a command line option to probe your hardware and create a local xorg.conf configuration file:
# Xorg -configure
You can then back up the existing /etc/X11/xorg.conf and copy the new xorg.conf to that directory.
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Xorg -configure may not work for all hardware configurations, such as RHEL 5 within VMware.
Assuming your X server is properly configured, you should be able to start a GUI with the startx command. One thing that can go wrong is the X Font Server. The X Window System needs fonts. Linux manages fonts through the X Font Server. RHEL manages the X Font Server with the xfs service script. Many different fonts are normally available in the /usr/share/X11/fonts directory.
The X Font Server can be an Achilles' heel for X Window. If you can't start the X Window, check the status of the X Font Server with the following command:
# service xfs status
If the X Font Server is not running, you'll want to go through the following troubleshooting list:
The xfs service could be stopped or dead. In this case, you may need to try restarting xfs.
The xfs service might not be set to start in your current runlevel; you can inspect and change this with the appropriate chkconfig command.
The filesystems with /tmp or /home could be full. The xfs service can't start if either of these filesystems is full. There may also be problems if /tmp is on a different physical hard disk from other X Window files.
Fonts could be missing from the default /usr/share/X11/fonts directory. For example, missing 100 dpi or 75 dpi fonts could cause applications in a Linux GUI to look strange.
The font configuration file, /etc/X11/fs/config, could be flawed. The simplest solution is to replace it from the associated RPM package, xorg-x11-xfs.
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If you want to use an existing RPM to restore a missing configuration (or other) file, install it with the --force switch. For example, if the /etc/X11/fs/config file is missing, you can replace it from the original RPM with the rpm -ivh --force xorg-x11-xfs-1*.rpm command.
Any of these problems could make trouble for the Linux X Window. While RHEL 5 is more resiliant to X Font Server problems, you still need to know how to fix them.
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Do not confuse the X Font Server service script, xfs, with the filesystem with the same initials, which was developed for very large files and partitions by Silicon Graphics.