2 Refer to Section 3.11, “/proc/tty/” for more information about tty devices.3 Refer to Section 5.2, “Runlevel 5” for more information about display managers.TipAfter the system is finished booting, it is possible to log in as root and executethese same scripts to start and stop services. For instance, the command/etc/rc.d/init.d/httpd stop stops the Apache HTTP Server.Each of the symbolic links are numbered to dictate start order. The order in which the servicesare started or stopped can be altered by changing this number. The lower the number, theearlier it is started. Symbolic links with the same number are started alphabetically.NoteOne of the last things the init program executes is the /etc/rc.d/rc.localfile. This file is useful for system customization. Refer to Section 3, “RunningAdditional Programs at Boot Time” for more information about using therc.local file.After the init command has progressed through the appropriate rc directory for the runlevel,the /etc/inittab script forks an /sbin/mingetty process for each virtual console (loginprompt) allocated to the runlevel. Runlevels 2 through 5 have all six virtual consoles, whilerunlevel 1 (single user mode) has one, and runlevels 0 and 6 have none. The /sbin/mingettyprocess opens communication pathways to tty devices2, sets their modes, prints the loginprompt, accepts the user's username and password, and initiates the login process.In runlevel 5, the /etc/inittab runs a script called /etc/X11/prefdm. The prefdm scriptexecutes the preferred X display manager3 — gdm, kdm, or xdm, depending on the contents ofthe /etc/sysconfig/desktop file.Once finished, the system operates on runlevel 5 and displays a login screen.3. Running Additional Programs at Boot TimeThe /etc/rc.d/rc.local script is executed by the init command at boot time or whenchanging runlevels. Adding commands to the bottom of this script is an easy way to performnecessary tasks like starting special services or initialize devices without writing complexinitialization scripts in the /etc/rc.d/init.d/ directory and creating symbolic links.The /etc/rc.serial script is used if serial ports must be setup at boot time. This script runsChapter 1. Boot Process, Init...8
