Installation guide

60 Chapter 3. Boot Process, Init, and Shutdown

After the init command has progressed through the appropriate rc directory for the runlevel, the

/etc/inittab script forks a getty process for each virtual console (login prompts) allocated to the

runlevel. Runlevels 2 through 5 get all six virtual consoles, while runlevel 1 (single user mode) gets

only one and runlevels 0 and 6 get none. The getty process opens communication pathways to tty

devices

, sets their modes, prints the login prompt, gets the user name, and initiates the login process

for the user.

In runlevel 5, /etc/inittab runs a script called /etc/X11/prefdm. The prefdm script runs the

preferred X display manager, gdm if you are running GNOME or kdm if you are running KDE, based

on the contents of the /etc/sysconfig/desktop/ directory.

Finally, the init command runs the /etc/rc.d/rc.local script.

At this point, you should be looking at a login prompt.

3.3. Running Programs at Boot Time

The ﬁle /etc/rc.d/rc.local script is run by the init command at boot time, or when changing

runlevels, after all other initialization is complete. You can use this ﬁle to add additional commands

necessary for your environment. For instance, you can start additional daemons or initialize a printer.

In addition, if you require serial ports setup at boot time, you can create and edit /etc/rc.serial.

This script runs setserial commands to conﬁgure the system’s serial ports. See the setserial

man page for more information.

3.4. Differences in the Boot Process of Other Architectures

Once the Red Hat Linux kernel loads and hands off the boot process to the init command, the same

sequence of events occurs on every architecture. So the main difference between each architecture’s

boot process is in the application used to ﬁnd and load the kernel.

For example, the Alpha architecture uses the aboot boot loader, while the Itanium architecture uses

the ELILO boot loader.

Consult the Ofﬁcial Red Hat Linux Installation Guide speciﬁc to these platforms for information on

conﬁguring their boot loaders.

3.5. SysV Init

The SysV init is a standard process used by Red Hat Linux to control which software the init com-

mand launches or shuts off on a given runlevel. SysV init chosen because it is easier to use and more

ﬂexible than the traditional BSD style init process.

The conﬁguration ﬁles for SysV init are in the /etc/rc.d/ directory. Within this directory, are the

rc, rc.local, and rc.sysinit scripts as well as the following directories:

init.d

rc0.d

rc1.d

rc2.d

rc3.d

rc4.d

rc5.d

rc6.d

4. See Section 2.3.11 for more information on tty devices.