One of the most important aspects of getting a Linux system up and running is configuring the user interface. As RHCEs and RHCTs are expected to configure computers for non-administrative users, the Red Hat exams test your ability to configure the X Window System, which is the foundation of the Linux graphical user interface (GUI). While the GUI plays an integral part of other operating systems such as Microsoft Windows, the X Window System on Linux is essentially just another application.
Many administrators don't even bother with the GUI; the command line interface is enough for most administrative purposes. However, regular users on a Linux workstation are more productive using the GUI and the multitude of X Window-based applications. If you are helping users migrate from Microsoft Windows to Linux, the X Window System allows you to provide a less intimidating environment.
Not all Linux computers require the X Window System. For example, computers that are used as dedicated DHCP, DNS, or NFS servers generally don't serve as workstations for anyone and therefore don't need any sort of GUI. Many Linux gurus are biased against the GUI. While Red Hat and others have developed some helpful GUI tools, they are almost always "front ends," or programs that customize one or more commands at the command line interface.
But if you're administering a network of Linux computers for regular users, you'll need to know how to administer the X Window System, a skill that requires a basic understanding of the available desktops and graphical applications.
Most Linux distributions (including RHEL) have converted display software from the XFree86 to the X.org system. While the names of the configuration files and some of the commands have changed, the basic settings and tools have not. If you learned to configure the X Window using XFree86, you should have no trouble configuring the X.org system.
This chapter starts with the X server, as configured on the local computer. It continues with X clients, as generic applications that you can run from the local or a remote network computer. Once everything is configured, you're ready to take a step back to the start process for the X Window. The chapter moves on to the two major Linux graphical desktops, and finally covers a very few of the available graphical applications.
The Linux Graphical User Interface
The Red Hat Exam Prep guide suggests that you need to know how to configure the X Window, presumably for non-administrative users. Remember that RHCE candidates must successfully complete all RHCT Troubleshooting and System Maintenance requirements, including configuring the X Window System and a desktop environment. You also need to know how to configure the X Window on a local computer. There are a number of reasons why the X Window may fail.
The X configuration files can be difficult to learn. It may be more efficient to use the Red Hat GUI X Window Display Settings configuration tool, which you can start with the system-config-display command. While Linux geeks generally shy away from GUI tools, you need to use the system that works most quickly for you.
The X Window System can work over a network. Once properly configured, you can run GUI applications from a remote computer. To make this work, you need to understand modularity of the X server and X clients, as well as the way X Window security is managed on your network.
I use the Red Hat Display Settings tool and system-config-display command interchangeably; the command is the fastest way to start the tool.