Introducing The X Window System

Warning

This article is badly out of date. It is retained for historical purposes only.

The X Window System is the graphical interface for Linux (and I think every other variant of UNIX, too). A word of caution for users of MS Windows: unless you are looking for fight, don’t ever call it “X Windows” around a UNIX person! Flame wars have raged for years over this. The proper term is “The X Window System.” If you must shorten it, call it X11, or just X. They’ll know what you mean. I will be using these terms interchangeably below.

Like everything else on Linux, the X Window System is based on a network paradigm. The program that actually controls your display, drawing the boxes and buttons you see, is called the X Server. Each X server is made for a specific video card, so there are several X servers to choose from. Programs that use the X server to display themselves on your screen are called X clients. Unlike MS Windows, the X server and X client can run on different computers and talk to each other across the network. This means that you can run a program on another machine and make it display itself on your own! (This is a fairly advanced topic and will not be covered in this article, I just thought I should mention it because it’s cool).

Obtaining XFree86

A version of the X Window System that runs on Intel platforms and is used in all Linux distributions (as well as FreeBSD and other free Unixes) is produced by the XFree86 Project. Obtaining it is usually not an issue, since it is included with the operating system distribution. Each distributor tweaks and tests the X Window System to work best with their distribution, so check with your Linux distributor for updates first. But if you need to upgrade in order to support a new video card, or if you just want to be on the cutting edge, you can always get the latest version in source or binary form at XFree86.org.

Installing and Configuring XFree86

In almost every case, the installation of XFree86 should be handled by your distribution’s setup utility during Linux installation. If you chose not to install it at the time you installed Linux, the package utility for your distribution should allow you to install it. See your distribution documentation for details.

Even after it is installed, you may still have some work to do before X will run properly. It needs to know about your video card and monitor so that it can use the correct X server and the optimal screen resolutions and refresh rates. Some distributions contain special tools for configuring X on your system. Red Hat uses the X Configurator to automatically detect information about your video card. To run it, become SuperUser and type setup at the terminal. (This setup utility can also be used to configure your sound card, system time, and other things as well). SuSE Linux has a utility called sax which performs this task. You can access it through the menus in Yast, the SuSE setup tool.

If these automated tools fail to get you up and running, or are not available in your distribution, you can configure XFree86 using tools that come in the XFree86 distribution.

XF86Setup

The easier of the two standard configuration utilities is XF86Setup (remember that Linux is case sensitive, so you must type the name exactly as it appears).

If it finds an existing XFree86 configuration file it will offer to use it as a starting point. Whether you do this is up to you, but if your X system is not working now, I would recommend starting over from scratch. It then informs you that it will try to switch into graphics mode. XF86Setup uses the VGA X server to host the graphical setup program. This server should run on any VGA compatible video card, but there are some cards that are not as compatible as they claim to be. If you don’t get something that looks like an XFree86 setup program, skip to the section on xf86config below.

If Linux was able to detect your mouse, it should already be working. If not, the first screen of XF86Setup explains how to use the program via the keyboard. The first screen is used to configure your mouse to work under X. Several types of mice are supported, but most will choose either Microsoft (for serial mice) or PS/2. From the “Mouse Device” list choose the port where your mouse is attached. PS/2 mice will be /dev/psaux while serial mice will probably be /dev/cua0. If your mouse is already working, do not change this setting. If you have a two-button mouse, I recommend pressing the button “Emulate 3 Buttons”. This simulates a middle mouse button click when you hit the left and right buttons at the same time. (Press the Apply button and try it). The middle mouse button is used in many X programs. You may also adjust the other settings to your liking.

The second screen allows you to choose a keyboard layout. The default will probably work, but if you have a “Windows-ready” keyboard you may want to pick the 104-key from the list. The picture of the keyboard will change as you select new ones, so you can just compare it to your own until something matches (or comes close). You can also adjust how the Shift, Control, and CapsLock keys work here. I recommend you stick with the defaults.

The next screen is the most vital, where you must select your video card. If you get this wrong, X will not work. The list of supported cards is quite extensive, so unless your card is a brand new model, it is likely to be found here. After you select your card, it is a good idea to read the README file for your card (just press the button). It will tell you about any special configuration options or bugs you should be aware of. The “Detailed Setup” option allows you to pick special configuration options, specify the RAMDAC or chip set for your card, and other details that are likely to confuse you completely. Don’t use it unless you have to.

On the next screen you must tell XFree86 about your monitor. Pick the highest resolution and refresh rate supported by your monitor (you should be able to find this information in your monitor documentation). If you have an old monitor, be careful not to over-estimate! While the new multi-frequency monitors will adjust themselves to the video card as needed and turn themselves off if there is a problem, older fixed-frequency monitors can be severely damaged (we’re talking smoke and flames here, literally) if you use a higher refresh rate than the monitor supports.

The next screen is for “Mode Selection”, where you will choose your default screen resolution and color depth. Normal resolution these days is 800x600, but you may want to use a higher resolution if your monitor supports it. You may choose more than one resolution, and X will allow you to switch between them, but I recommend using only one to start with. The color depth setting is at the bottom of the screen; 8bpp (Bits Per Pixel) is 256 colors, faster but not that pretty for photographs or clean fades; 16bpp is “high color”, 64 thousand colors, much prettier; 24bpp or higher is “true color”, excellent for editing photos. The choice is yours, but here you must choose only one.

The final screen allows you to adjust other options for your X Window System. The defaults should be fine. I highly recommend that you enable the first option, “Allow server to be killed with hotkey sequence (Ctrl-Alt-Backspace)”. This is your emergency escape hatch from X in case something hangs and the interface stops responding. (While Linux itself is rock solid stable, some of the programs you install might not be so great!)

Once you’ve filled out all the screens to your satisfaction, press the “Done” button at the bottom. XF86Setup then gives you a chance to change your mind in case you hit “Done” by accident. If you press “Okay”, it will attempt to run your X server with the new settings. If all goes well, you will see a (rather ugly) graphical screen running at your default resolution and color depth, and a Congratulations message. If you see scrambled eggs instead, something was not configured correctly. Press Ctrl-Alt-Backspace to kill the X server. You’ll get an error message. Start over again.

If the Congratulations message is visible, you have the option of using the xvidtune utility to adjust the image on your screen. (If your monitor has controls to adjust the image, use those control instead). Once you are satisfied, you can save the configuration to the default configuration file, or to a file under another name if you prefer. A backup copy of the original will be saved if it exists. You will then be returned to the command prompt. Type startx and enjoy the show!

xf86config

If XF86Setup will not work on your computer for some reason, you can fall back to the old text-based method for configuring XFree86. Type xf86config to start the script. Read each screen carefully, as the messages contain important clues about answering the questions. At any time you can press Ctrl-C to abort the process.

The first question asks you to choose your mouse type from a menu. Serial mice are probably type 1, Microsoft compatible. Next it asks whether you want your two-button mouse to emulate three buttons. This simulates a middle mouse button click when you hit the left and right buttons at the same time. The middle mouse button is used in many X programs. I recommend answering YES.

Next you are asked to type the name of the device where your mouse is connected. The default /dev/mouse may not work if Linux did not detect your mouse during installation. PS/2 mice will be /dev/psaux while serial mice will probably be /dev/cua0. If your mouse is already working, do not change this setting. Just take the default.

Next you are asked whether you want to use the XKB keyboard extension. Answer yes, and select the appropriate keyboard layout from the menu. Most folks can get by with option 1, the standard 101-key US keyboard.

The next step asks to configure your monitor. You will need to have your monitor manual handy to get the horizontal and vertical refresh rates required here. For the horizontal sync range, if you cannot find this exact information, choose the line that corresponds to the highest resolution and refresh rate supported by your monitor. If you have an old monitor, be careful not to over-estimate! While the new multi-frequency monitors will adjust themselves to the video card as needed and turn themselves off if there is a problem, older fixed-frequency monitors can be severely damaged (we’re talking smoke and flames here, literally) if you use a higher refresh rate than the monitor supports. For the vertical refresh rate, if you cannot find the exact numbers, the 50-90 range should work on most monitors. If you have an especially old monitor, you may want to pick the smallest range just to be safe.

You are then asked to provide identification or description strings for your monitor, vendor, and model. These names are optional. If you know them, go ahead and fill them in, if not just hit enter.

Next comes the vital part, where you are asked about your video card. You are given the option to select a video card from the card database. If you want to get this working, answer YES here. You will then be presented with a list of video cards. This list contains hundreds of cards and there is no way to back up, so read the list carefully and choose the correct video card for your system. When you see your card, type its number and press enter. Information from the card database about your card will be displayed. Note any special tips given here, such as “Do NOT probe clocks”. This may mean something later in the process. If this is the correct card, press enter. If not, you must press Ctrl-C and start the whole process over again.

The next screen will ask you which X server to run. If you found your card on the list, you should have 5 options, the fifth being “Choose the server from the card definition”. Always pick this option if it is available. If this option is not present, it may mean your video card is unsupported. You can try using one of the first 3 servers, but there is no guarantee that any of them will work. In fact, if XF86Setup failed, they probably won’t. Visit the XFree86 web site to find out about X support for your card, or contact the card manufacturer for more information on chip set compatibility.

After picking the X server, you will be asked whether you want to set the symbolic link to your server. Always answer YES. Then you will be asked about the amount of video memory on your card. Choose the appropriate value (given here in kbytes). Next you are asked to enter description strings for your video card. Again, these are optional, press enter to use the defaults. Next you are asked to select a RAMDAC. Unless you know for certain which RAMDAC is on your video card, press “q” to quit this step without choosing one. Most X servers will autodetect this setting properly anyway. The next screen asks about clock chips. My advice here is the same, press enter to continue. Then you will be asked if you want X to probe for clocks. If your card definition in the database said don’t do this (I told you that would come up later) then don’t. It could crash your system. If in doubt, skip it.

Finally, you are given the opportunity to choose your default screen resolution and color depth. The configuration script will have some default resolutions listed based on the capabilities of your card. Normal resolution these days is 800x600, but you may want to use a higher resolution if your monitor supports it. You may choose more than one resolution via the menus, which are self-explanatory. X will allow you to switch between the different resolutions you choose, but I recommend using only one to start with. The first resolution listed will be the default.

The color depth settings are: 8bpp (Bits Per Pixel) is 256 colors, faster but not that pretty for photographs or clean fades; 16bpp is “high color”, 64 thousand colors, much prettier; 24bpp or higher is “true color”, excellent for editing photos. The choice is yours, but again the first one listed is the default.

Once you are satisfied with your mode settings, choose the last option and you will be asked if you want to save the XF86Config file. Answer YES, and you are back at the command prompt. If everything went well, you can type startx and enjoy the show!