Runlevel 5 - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Chapter 31. The X Window System
When the startx command is executed, it searches for the .xinitrc file in the user's home
directory to define the desktop environment and possibly other X client applications to run. If no
.xinitrc file is present, it uses the system default /etc/X11/xinit/xinitrc file instead.
The default xinitrc script then searches for user-defined files and default system files, including
.Xresources, .Xmodmap, and .Xkbmap in the user's home directory, and Xresources, Xmodmap,
and Xkbmap in the /etc/X11/ directory. The Xmodmap and Xkbmap files, if they exist, are used
by the xmodmap utility to configure the keyboard. The Xresources file is read to assign specific
preference values to applications.
After setting these options, the xinitrc script executes all scripts located in the /etc/X11/xinit/
xinitrc.d/ directory. One important script in this directory is xinput.sh, which configures settings
such as the default language.
Next, the xinitrc script attempts to execute .Xclients in the user's home directory and turns to
/etc/X11/xinit/Xclients if it cannot be found. The purpose of the Xclients file is to start the
desktop environment or, possibly, just a basic window manager. The .Xclients script in the user's
home directory starts the user-specified desktop environment in the .Xclients-default file. If
.Xclients does not exist in the user's home directory, the standard /etc/X11/xinit/Xclients
script attempts to start another desktop environment, trying GNOME first and then KDE followed by
twm.
When in runlevel 3, the user is returned to a text mode user session after ending an X session.

31.5.2. Runlevel 5

When the system boots into runlevel 5, a special X client application called a display manager is
launched. A user must authenticate using the display manager before any desktop environment or
window managers are launched.
Depending on the desktop environments installed on the system, three different display managers are
available to handle user authentication.
• GNOME — The default display manager for Red Hat Enterprise Linux, GNOME allows the user to
configure language settings, shutdown, restart or log in to the system.
• KDE — KDE's display manager which allows the user to shutdown, restart or log in to the system.
• xdm — A very basic display manager which only lets the user log in to the system.
When booting into runlevel 5, the prefdm script determines the preferred display manager by
referencing the /etc/sysconfig/desktop file. A list of options for this file is available in this file:
/usr/share/doc/initscripts-<version-number>/sysconfig.txt
where <version-number> is the version number of the initscripts package.
Each of the display managers reference the /etc/X11/xdm/Xsetup_0 file to set up the login
screen. Once the user logs into the system, the /etc/X11/xdm/GiveConsole script runs to assign
ownership of the console to the user. Then, the /etc/X11/xdm/Xsession script runs to accomplish
many of the tasks normally performed by the xinitrc script when starting X from runlevel 3,
including setting system and user resources, as well as running the scripts in the /etc/X11/xinit/
xinitrc.d/ directory.
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