[Chapter 5] 5.3 Configuring X

5.3 Configuring X

When you install the xserver-common package, xf86config is automatically launched. However, you can launch the program any time you like. To do so, log in as root and type the command:

 xf86config

Figure 5.1 shows the beginning of the xf86config dialog. As you can see, xf86config is a text-mode program; it does not support use of the mouse and it presents its questions teletype-style, using black-and-white text.

In working with xf86config, you may find that your Backspace key doesn't work as expected. If so, use Ctrl-Backspace instead.

Figure 5.1: The beginning of the xf86config dialog

Next, xf86config asks you to specify the type of mouse attached to your system, as shown in Figure 5.2. Type the number associated with your choice, and press Enter. For non-mouse pointing devices found on many laptops, you should most likely select PS/2 Mouse.

Figure 5.2: Specifying the mouse type

If you selected the Logitech MouseMan mouse, you should enable its third button by responding y to the question asking whether ChordMiddle should be enabled, as shown in Figure 5.3.

Figure 5.3: Specifying the ChordMiddle option

If your mouse has only two buttons, you should enable emulation of a three-button mouse by responding y to the question asking about Emulate3Buttons, as shown in Figure 5.4. If you enable this option you can simultaneously press both the buttons of your mouse to emulate pressing the third button.

Figure 5.4: Specifying emulation of a three-button mouse

Next, you must specify the device file associated with the mouse, as shown in Figure 5.5. The install program should have associated your system's mouse with the device /dev/mouse, which is the default choice. Simply press Enter to continue.

Figure 5.5: Specifying the mouse device

As described by the output shown in Figure 5.6, X provides special support for using extended keyboards. If you use a special keyboard layout to support national characters, you can type y to use xkb, which simplifies changing the keyboard map. After making your choice, press Enter to continue.

Figure 5.6: Specifying use of the keyboard extension

As shown in Figure 5.7, xkb supports a variety of keyboard encodings, or keymaps. Type the number that corresponds to the type of keyboard attached to your system, and press Enter.

Figure 5.7: Specifying the keymap

Next, as shown in Figure 5.8, you must specify two characteristics of your system's monitor: its vertical refresh rate (VertRefresh) and horizontal sync rate (HorizSync). You can find these values by:

Consulting your monitor's documentation
Consulting the file /usr/doc/xserver-common/Monitors.gz, which may list your monitor. Use gunzip to uncompress the file and ae or another text editor to view it.
Viewing the monitor's manufacturer's web support page
Posting a question to the newsgroup comp.os.linux.setup
Contacting the monitor manufacturer's technical support group and requesting the information

To specify the monitor's characteristics, press Enter.

Figure 5.8: Preparing to specify monitor characteristics

First, you must specify the horizontal sync rate of your monitor, as shown in Figure 5.9. Type the number associated with your choice and press Enter. If you're unsure of your monitor's horizontal sync range, but certain that it supports 800×600 resolution, specify range 2. To specify a range other than those listed, you can select choice 11; if you do so, you'll be prompted to enter the low and high values of the horizontal sync range.

WARNING: Often, otherwise similar monitor models have different horizontal sync rates. It is crucial that you accurately determine the horizontal sync rate of your monitor. If you configure X to use an inappropriate horizontal sync rate, you can permanently damage your monitor.

Figure 5.9: Specifying the horizontal sync rate

Next, as shown in Figure 5.10, you must specify the vertical sync (refresh) rate. Type the number associated with your choice and press Enter. If you're unsure of your monitor's vertical sync range, specify range 1, which is the most conservative. To specify a range other than those listed, you can select choice 5; if you do so, you'll be prompted for the low and high values of the vertical sync range.

Figure 5.10: Specifying the vertical sync rate

You must now specify identification and description strings for your monitor, as shown in Figure 5.11. You can enter any text you like. Press Enter after typing each string.

Figure 5.11: Specifying the monitor identification and description strings

Next, you must specify your video card and its characteristics. The explanations provided by xf86config, shown in Figure 5.12, point out that you can choose to select your card from a database. However, even if you do so, you'll be given the opportunity to specify non-standard values. Unless you have a specific reason for doing so, you should not override the values in the database. Moreover, you should be careful to choose only the database entry that exactly matches your card; cards having similar model names may have significantly different hardware characteristics.

Figure 5.12: Preparing to examine the card database

Figure 5.13 shows the screen you use to choose your card. Simply type the number associated with your card and press Enter. If you suspect that your card appears on a subsequent page, press q to page forward through the database. If you accidentally page past your card, simply continue moving forward; when the program reaches the last entries of the database, it cycles back to the beginning.

Figure 5.13: Examining the card database

After you choose your video card, xf86config reports your choice. As in Figure 5.14, xf86config may provide instructions, such as "Do NOT probe clocks." It's a good idea to write these down so that you remember to observe them even after they've scrolled off the screen.

Figure 5.14: The selected card definition

Next, you must specify the X server you want to use, as shown in Figure 5.15. Consult Table C.1 to determine the appropriate server. Type the number associated with the server and press Enter to continue. If you specify choice 4, you'll be prompted to specify which accelerated server you want to use. If you're in doubt, specify server 3, the XF86_SVGA server; unless your video card or monitor are quite old, they're likely to support 256-color SVGA.

Figure 5.15: Specifying the server

Next, as shown in Figure 5.16, xf86config asks whether it should change the first line of the /etc/X11/server file to point to your server. Respond by typing y and pressing Enter.

Figure 5.16: Setting the default server

Now, as shown in Figure 5.17, specify the amount of memory installed on your video card by typing the appropriate number and pressing Enter. You can determine the amount of memory by examining the documentation that accompanied your card. If you cannot locate the documentation, try a small value, such as 1024K. Generally, choosing too small a value will merely prevent your card from operating at high resolutions; however, choosing too large a value may cause the card to temporarily malfunction.

Figure 5.17: Specifying the amount of video memory

Just as you previously specified text strings that identify and describe your monitor, you should now specify strings that identify and describe your video card, as shown in Figure 5.18. Press Enter after typing each string.

Figure 5.18: Specifying the video card identification and description strings

If you selected an accelerated server, you can now enter the RAMDAC settings, as shown in Figure 5.19. Some SVGA servers also support RAMDACs. If you're not using an accelerated server, you can simply type q and press Enter to omit specification of a RAMDAC. Otherwise, type the number associated with the RAMDAC used by your card and press Enter. Determining the correct number may pose a bit of a puzzle. The descriptions given in the screen specify RAMDAC chips used on particular cards. If you can conveniently view your card, you can inspect it to see if it contains any of the listed chips. If it's not convenient to view your card, type q and press Enter to omit specification of a RAMDAC. X will autodetect most RAMDACs, so omitting the specification will not likely impair the performance of your video hardware.

Figure 5.19: Specifying the RAMDAC settings

Next, as shown in Figure 5.20, you can specify the programmable clock chip used by your video card. Most video cards lack such a chip; such cards require a Clocks line in the X configuration file. If your video card lacks a programmable clock chip, type q and press Enter to continue; otherwise type the number associated with your card's programmable clock chip and press Enter.

Figure 5.20: Specifying the clock chip

As shown in Figure 5.21, xf86config asks you to let it probe your system to determine proper clock timings. If you specified a programmable clock chip, you should omit the probe; type n and press Enter to continue. You should also omit the probe if you earlier noted that probing is not recommended for your card.

You can sometimes improve the accuracy of the clock timings by running the probe yourself after xf86config is done and adding an appropriate Clocks line to your X configuration. Consult the X documentation for information on how to do so.

Otherwise, you should let xf86config probe your system to determine appropriate clock settings: type y and press Enter to begin the probe.

WARNING: If xf86config probes your system and the screen remains black for more than 30 seconds, immediately cancel the probe by turning off the monitor, pressing Ctrl-C, and restoring power to your monitor. If the probe fails, it can permanently damage your monitor.

Figure 5.21: Beginning the automatic probe

Next, you can specify the color depths and resolutions in which X will operate, as shown in Figure 5.22. Generally, xf86config's default choices are appropriate: you can type 5 and press Enter to continue. However, you can change the resolutions allowed when operating at a given color depth by typing the number associated with the color depth and specifying the desired resolution or resolutions.

Figure 5.22: Specifying the modes

Finally, as shown in Figure 5.23, xf86config is ready to write the configuration file it has prepared. Generally, you should let it write the file to /etc/X11/XF86Config; simply type y and press Enter. However, if you prefer, you can type n and specify a different directory or filename.

Figure 5.23: Writing the configuration file

Once the file has been written, you're ready to start X.