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C.5. Runlevels and X
In most cases, the Red Hat Enterprise Linux installer configures a machine to boot into a graphical login environment, known as runlevel 5. It is possible, however, to boot into a text-only multi-user mode called runlevel 3 and begin an X session from there.
The following subsections review how X starts up in both runlevel 3 and runlevel 5. For more information about runlevels, see Section 12.1, “Configuring the Default Runlevel”.
C.5.1. Runlevel 3
When in runlevel 3, the best way to start an X session is to log in and type
startx
. The startx
command is a front-end to the xinit
command, which launches the X server (Xorg
) and connects X client applications to it. Because the user is already logged into the system at runlevel 3, startx
does not launch a display manager or authenticate users. See Section C.5.2, “Runlevel 5” for more information about display managers.
- 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, andXresources
,Xmodmap
, andXkbmap
in the/etc/X11/
directory. TheXmodmap
andXkbmap
files, if they exist, are used by thexmodmap
utility to configure the keyboard. TheXresources
file is read to assign specific preference values to applications. - After setting the above options, the
xinitrc
script executes all scripts located in the/etc/X11/xinit/xinitrc.d/
directory. One important script in this directory isxinput.sh
, which configures settings such as the default language. - 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 theXclients
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, then KDE, followed bytwm
.
When in runlevel 3, the user is returned to a text mode user session after ending an X session.