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Chapter 3. Boot Process, Init, and Shutdown

them to quickly move in and out of their custom configuration without disturbing the normal set of

features at the standard runlevels.

If your machine gets into a state where it will not boot due to a bad

/etc/inittab

or will not let you

log in because you have a corrupted

/etc/passwd

or if you have simply forgotten your password,

you can boot into single user mode.

If you are using LILO, you can enter single user mode by typing linux single at the LILO

boot:

prompt.

If you are using GRUB as your boot loader, you can enter single user mode using the following steps.

In the graphical GRUB boot loader screen, select the Red Hat Linux boot label and press [e] to

edit it.

Arrow down to the kernel line and press [e] to edit it.

At the prompt, type single and press [Enter].

You will be returned to the GRUB screen with the kernel information. Press the [b] key to boot the

system into single user mode.

A very bare system will boot, and you will have a command shell from which you can fix things.

If this does not work, you will need to boot by typing linux init=/bin/bash at the LILO

boot:

prompt. This places you at a shell prompt; note that no file systems other than the root file

system are mounted, and the root file system is mounted in read only mode. To mount it in read write

mode (to allow editing of a broken

/etc/inittab

, for example) do:

mount  n /proc

mount  o rw,remount /

3.6.1. Initscript Utilities

The

/sbin/chkconfig

utility

is a simple command line

tool for maintaining

the

/etc/rc.d/init.d

directory hierarchy. It relieves system administrators from having to directly

manipulate the numerous symbolic links in the directories under

/etc/rc.d

.

In addition, there is /sbin/ntsysv that provides a text based interface, which you may find easier to

use than

chkconfig

's command line interface.

If you prefer a graphical interface, use the Services Configuration Tool program, which can be in 

voked using the

redhat config services

command.

All of these utilities must be run as root.

Please refer to the chapter titled Controlling Access to Services in Official Red Hat Linux Customiza 

tion Guide for more information regarding these tools.

Next, we will discuss information in the files within the

/etc/sysconfig/

directory which define

the parameters used by some services when they start up.

3.7. The

/etc/sysconfig/

Directory

The following information outlines some of the files found in the

/etc/sysconfig/

directory, their

function, and their contents. This information is not intended to be complete, as many of these files

have a variety of options that are only used in very specific or rare circumstances.

The

/usr/share/doc/initscripts  version number /sysconfig.txt

file contains a

more authoritative listing of the files found in the

/etc/sysconfig

directory and the configuration

options available.