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The Command-Line Interface (CLI) versus the Graphical User Interface (GUI)
Red Hat Linux installs the X Window System by default. You can perform most administrative tasks with the GUI-based tools (GUI stands for graphical user interface) that Red Hat provides. Most of the how-to instructions in this book use the X-based applications and utilities. We do that because they’re generally easier to use and because this book wasn’t written for systems administrators.
Occasionally, a utility or program doesn’t run graphically; at other times, using nongraphical methods and systems is just more interesting or convenient. Believe it or not, some geekier Linux users prefer to use a text-based, command-line interface (CLI). If you’re not familiar with doing some basic administrative tasks with a CLI, we don’t recommend using one just to prove that you can. Being less of a geek is okay. We still like and respect you. On the other hand, it makes good sense to know some basics, just in case a need arises for you to have to wing it with the text-based interface.
Command-line interfaces are generally run from a shell, which acts as a text-based interface between the Red Hat Linux operating system and you. The bash shell, which Red Hat Linux uses by default, displays a prompt like [lidia@cancun lidia]$. You enter commands at the shell prompt. That’s where the term command-line interface (or CLI) comes from.
You can start a shell from within the GNOME interface by starting a GNOME Terminal (also known generically as a terminal emulator). Click the GNOME Menu and then choose System ToolsTerminal (you can also right-click anywhere on the GNOME Desktop and choose New Terminal) to start a terminal session, as shown in Chapter 9.)
Figure 4-2: A GNOME Terminal session.
You can run individual programs without starting an interactive shell by using the GNOME Run Program menu. Click the GNOME Menu button — the red hat in the lower-left corner of the screen — and choose Run Program. The Run Program window opens; type the name of any program in the text box. The program then runs — if it’s graphically oriented. You don’t see the output if the program is designed to interact with the terminal screen (the technical term is standard output). Entering xclock, for example, displays a graphical clock on your screen.
TipThe GNOME Menu button looks like a red hat and is on the toolbar in the lower-left corner of your desktop. The button works in a manner similar to the Windows Start button.
Technical StuffThe GNOME Terminal is similar to the MS-DOS window in Windows. Opening an MS-DOS window provides a CLI in which to enter DOS commands. The underlying technology of a Windows CLI is different from that of a Linux CLI. However, its capabilities are more or less the same.
