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Chapter 9 . Using X 365 This large section combines several variables and loads the correct keymaps. # run all system xinitrc shell scripts. for i in /etc/X11/xinit/xinitrc.d/* ; do if [ -x $i ]; then . $i fi done # now, we see if xdm/gdm/kdm has asked for a specific environment case $# in 1) case $1 in failsafe) exec xterm -geometry 80×24-0-0 ;; gnome) exec gnome-session ;; kde) exec startkde ;; anotherlevel) # we assume that switchdesk is installed. exec /usr/share/apps/switchdesk/Xclients.anotherlevel ;; esac esac # otherwise, take default action if [ -x $HOME/.xsession ]; then exec $HOME/.xsession elif [ -x $HOME/.Xclients ]; then exec $HOME/.Xclients elif [ -x /etc/X11/xinit/Xclients ]; then exec /etc/X11/xinit/Xclients else # should never get here; failsafe fallback exec xsm fi Finally, this section starts the appropriate desktop interface. If the system does not use one of the specified desktops, the xsmcommand is issued, which starts a basic X session. Xresources The XDM login screen can be customized with the Xresourcesfile that is referenced in the Xsession file. This file uses the standard Xresource format, which is discussed in more detail in the Customizing X applications section later in the chapter. ! $XConsortium: Xresources /main/8 1996/11/11 09:24:46 swick $ xlogin*login.translations: #override CtrlR: abort-display()n
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364 Part II . Getting Around in Linux These lines are similar to those in the xinitrcfile and specify the files for several variables. Notice the path that this script uses for the Xresources file, in case you need to customize it. # merge in defaults if [ -f $oldsysresources ]; then xrdb -merge $oldsysresources fi if [ -f $sysresources ]; then xrdb -merge $sysresources fi if [ -f $userresources ]; then xrdb -merge $userresources fi # merge in keymaps if [ -f $sysxkbmap ]; then setxkbmap `cat $sysxkbmap ` XKB_IN_USE=yes fi if [ -f $userxkbmap ]; then setxkbmap `cat $userxkbmap ` XKB_IN_USE=yes fi if [ -z $XKB_IN_USE -a ! -L /etc/X11/X ]; then if grep ^exec.*/Xsun /etc/X11/X > /dev/null 2>&1 && [ -f /etc/X11/XF86Conf ig ]; then xkbsymbols=`sed -n -e s/^[ ]*XkbSymbols[ ]* (.*) .*$/1/p /etc /X11/XF86Config` if [ -n $xkbsymbols ]; then setxkbmap -symbols $xkbsymbols XKB_IN_USE=yes fi fi fi # xkb and xmodmap don t play nice together if [ -z $XKB_IN_USE ]; then if [ -f $oldsysmodmap ]; then xmodmap $oldsysmodmap fi if [ -f $sysmodmap ]; then xmodmap $sysmodmap fi if [ -f $usermodmap ]; then xmodmap $usermodmap fi fi unset XKB_IN_USE
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Chapter 9 . Using X 363 DisplayManager*resources: /etc/X11/xdm/Xresources DisplayManager*session: /etc/X11/xdm/Xsession DisplayManager*authComplain: false ! SECURITY: do not listen for XDMCP or Chooser requests ! Comment out this line if you want to manage X terminals with xdm DisplayManager.requestPort: 0 Xsession The XDM application uses the Xsession script file to know which desktop to give a user after they log in. It has many of the same commands as the xinitrc file and performs a similar function for those starting X with XDM. The following is an example of Xsessiontaken from a Red Hat system, with comments. Exam Tip The Xsession file decides which window manager to use when logging in with XDM. #!/bin/bash -login # (c) 1999, 2000 Red Hat, Inc. # redirect errors to a file in user s home directory if we can for errfile in $HOME/.xsession-errors ${TMPDIR-/tmp}/xses-$USER /tmp/xses-$ USER do if ( cp /dev/null $errfile 2> /dev/null ) then chmod 600 $errfile exec > $errfile 2>&1 break fi done This section creates a file named .xsession-errors in the user s home directory, which is used to log any errors. xsetroot -solid #356390 This sets the desktop background to a solid color. # clean up after xbanner if [ -x /usr/X11R6/bin/freetemp ]; then /usr/X11R6/bin/freetemp fi userresources=$HOME/.Xresources usermodmap=$HOME/.Xmodmap sysresources=/etc/X11/xinit/Xresources sysmodmap=/etc/X11/xinit/Xmodmap # backward compatibility oldsysresources=/etc/X11/xinit/.Xresources oldsysmodmap=/etc/X11/xinit/.Xmodmap
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362 Part II . Getting Around in Linux Exam Tip Tip Both KDE and GNOME provide their own XDM replacements, which look better and provide more functionality. The new display managers are used by default when the environments are installed. Enabling and disabling XDM When enabled, the xdmapplication is started at boot by a runlevel script. Debian just adds the S99XDMscript to runlevel 2. With Red Hat, the default runlevel is changed from 3 to 5 to enable xdm. To disable XDM you need either to remove the startup script in Debian or to change the runlevel from 5 to 3 in Red Hat. This can quickly be done with a telinit 3 command. The xdm process is started from a runlevel script in distributions that use Sys V init. Configuring XDM XDM can be difficult and complicated to configure, since it has several files that must be maintained. The following sections cover the most important files to look at when dealing with XDM. xdm-config The main configuration file for XDM is xdm-config. This file sets the basic operation of xdm. For most installations it should never be changed, but if you configure your system to allow remote logins, you may need to make some adjustments. That is covered in more detail in the next section. The following is a sample of an xdmconfig file. ! $XFree86: xc/programs/xdm/config/xdm-conf.cpp,v 1.1.1.2.4.2 1999/10/12 18:33:2 9 hohndel Exp $ ! ! $XConsortium: xdm-conf.cpp /main/3 1996/01/15 15:17:26 gildea $ DisplayManager.errorLogFile: /var/log/xdm-error.log DisplayManager.pidFile: /var/run/xdm.pid DisplayManager.keyFile: /etc/X11/xdm/xdm-keys DisplayManager.servers: /etc/X11/xdm/Xservers DisplayManager.accessFile: /etc/X11/xdm/Xaccess ! All displays should use authorization, but we cannot be sure ! X terminals will be configured that way, so by default ! use authorization only for local displays :0, :1, etc. DisplayManager._0.authorize: true DisplayManager._1.authorize: true ! The following three resources set up display :0 as the console. DisplayManager._0.setup: /etc/X11/xdm/Xsetup_0 DisplayManager._0.startup: /etc/X11/xdm/GiveConsole DisplayManager._0.reset: /etc/X11/xdm/TakeConsole !
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Chapter 9 . Using X 361 Exam Tip The startx command is a script that executes the xinit process. The xinitrc and .xinitrc files A script file is executed whenever the xinit process starts up. Each user can create his or her own personal .xinitrc in their home directory. If this file does not exist, the system-wide xinitrc stored in /etc/X11/xinit or /usr/X11/xinit/ xinitrc will be used. If you put multiple tasks in your .xinitrc file, the last one should not be sent to the background or the X server may exit. Exam Tip A user s .xinitrc script is run when a user starts X with the startx command. If no .xinitrc is found, the xinit process runs the system-wide xinitrc script. The Xclients and .Xclients files Some distributions have the xinitrcfile call the Xclientsscript file. Red Hat uses this file to test and see which window managers are installed and to run the one that you have configured as your preference. A user may have his or her own Xclients file in ~/.Xclients. Using XDM An alternative to booting to text mode and manually running startx is to run a display manager. There are several display managers available, but XFree comes with XDM. It is shown in Figure 9-10. XDM lets you boot up to a GUI login screen and go directly into X. When you exit out of X you are brought back to the GUI login screen. Figure 9-10: XDM
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360 Part II . Getting Around in Linux startx This startx command is actually a script that sets several variables and finally calls the xinit application. The following is an example of a startxscript with comments. #!/bin/sh # # (c) 1999 Red Hat Software, Inc. bindir=/usr/X11R6/bin userclientrc=$HOME/.xinitrc userserverrc=$HOME/.xserverrc sysclientrc=/etc/X11/xinit/xinitrc sysserverrc=/etc/X11/xinit/xserverrc clientargs= serverargs= This sets several variables that point to other script files that get called later. if [ -f $userclientrc ]; then clientargs=$userclientrc else if [ -f $sysclientrc ]; then clientargs=$sysclientrc fi fi if [ -f $userserverrc ]; then server=$userserverrc else if [ -f $sysserverrc ]; then server=$sysserverrc fi fi These lines do a test -fcheck to see if the files in the previous variables exist. The next section, omitted here, executes the script files stored in the variables. These are the xinitrc and xserverrcfiles. # set up default Xauth info for this machine mcookie=`mcookie` serverargs= $serverargs -auth $HOME/.Xauthority xauth add $display . $mcookie xauth add `hostname -f`$display . $mcookie This block sets up the X security information by executing xauth. The xauth tool is covered in more detail later in this chapter. xinit $clientargs — $server $display $serverargs Finally, the startx script executes xinit.
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Chapter 9 . Using X 359 For example, to create the necessary files for /usr/X11R6/lib/X11/fonts/ newfonts, you would run the following: mkfontdir /usr/X11R6/lib/X11/fonts/newfonts When this command runs, it creates the fonts.dir file. The following is an example of this file: UTI___14.pcf.gz -adobe-utopia-regular-i-normal–15-140-75-75-p-79-iso8859-1 UTI___24.pcf.gz -adobe-utopia-regular-i-normal–25-240-75-75-p-133-iso8859-1 courO08.pcf.gz -adobe-courier-medium-o-normal–8-80-75-75-m-50-iso8859-1 Another file that is used in the font directories is fonts.alias. It is a hand-created file that consists of two columns separated by a white space such as a space or tab. The first column contains the alias and the second column contains a font name or pattern to match. Once the new font files are created, you need to instruct the running X server to reread the font directories. This is done with the xset command. To have it reread the font directories you would use the following: xset fp rehash Exam Tip The mkfontdir command must be run whenever new fonts are added to your system. Starting X Objective 2.10 X Setup XDM. Turn xdm on and off, change the xdm greeting, change default bit- planes for xdm, set-up xdm for use by X-stations You can run X on your system in two ways. The first method is to invoke it manually from the command line after login. The second way is to have the system boot into a graphical mode with a GUI login. Starting X manually The X Window System can be manually started with the startxcommand. The next several sections follow the flow of scripts that begins when the user executes startx. The problem is that distributions vary on the exact path they take through the startup scripts and on what each script calls. It is recommended that you walk through the scripts for your distribution and version to know exactly what happens. Plus, it s excellent experience!
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358 Part II . Getting Around in Linux Figure 9-9: xvidtune Configuring fonts The X font server keeps track of all of the fonts installed on a system and lets a client use them, either locally or from across the network. Usually the font server does its work in the background, but when new fonts are added you need to make sure the font server is notified. The X server knows to get fonts from the font server with the following entry in the XF86Config file: FontPath unix/:-1 The syntax for this is as follows: FontPath
/:
This example tells the X server to use the font server on the local system, since the unix transport, no hostname, and the -1port is used. If you use a network font server, you would need to change this line. For example, suppose you have a font server named font.ournetwork.com listening on port 7100. You would use this directive: FontPath tcp/font.ournetwork.com:7100 Font files are stored in the /usr/X11R6/lib/X11//fonts directory tree. Each subdirectory off this tree contains fonts and a couple of files that tell the X server about the fonts installed. If you install new fonts, you need to run mkfontdir to create these files. The syntax for mkfontdir is as follows: mkfontdir
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