Chapter 3. Boot Process, Init, and Shutdown

59

S40atd  > ../init.d/atd

S45pcmcia  > ../init.d/pcmcia

S55sshd  > ../init.d/sshd

S56rawdevices  > ../init.d/rawdevices

S56xinetd  > ../init.d/xinetd

S60lpd  > ../init.d/lpd

S75keytable  > ../init.d/keytable

S80isdn  > ../init.d/isdn

S80sendmail  > ../init.d/sendmail

S85gpm  > ../init.d/gpm

S90canna  > ../init.d/canna

S90crond  > ../init.d/crond

S90FreeWnn  > ../init.d/FreeWnn

S90xfs  > ../init.d/xfs

S95anacron  > ../init.d/anacron

S95firstboot  > ../init.d/firstboot

S97rhnsd  > ../init.d/rhnsd

S99local  > ../rc.local

S99mdmonitor  > ../init.d/mdmonitor

As you can see, none of the scripts that actually start and stop the services are located in the

/etc/rc.d/rc5.d/

directory. Rather, all of the files in

/etc/rc.d/rc5.d/

are symbolic links

pointing to scripts located in the

/etc/rc.d/init.d/

directory. Symbolic links are used in each of

the

rc

directories so that the runlevels can be reconfigured by creating, modifying, and deleting the

symbolic links without affecting the actual scripts they reference.

The name of each symbolic link begin with either a

K

or an

S

. The

K

links are processes that are killed

on that runlevel, while those beginning with an

S

are started.

The

init

command first stops all of the

K

symbolic links in the directory by issuing the

/etc/rc.d/init.d/ command

stop

command, where

command

is the process to be

killed. It then starts all of the

S

symbolic links by issuing

/etc/rc.d/init.d/ command

start

.

Tip

After the system is finished booting, you can log in as root and execute these same scripts to start

and stop services. For instance, the command /etc/rc.d/init.d/httpd stop will stop the Apache

Web server.

Each of the symbolic links are numbered to dictate start order. You can change the order in which the

services are started or stopped by changing this number. Those symbolic links with the same number

are started alphabetically.

In the example

/etc/rc.d/rc5.d/

directory above, the

init

command will kill

pppoe

,

innd

,

ntpd

,

httpd

,

mysqld

,

pvmd

,

rarpd

,

bootparamd

,

nfs

,

rstatd

,

rusersd

,

rwalld

,

rwhod

,

squid

,

amd

,

mcserv

,

yppasswdd

,

dhcpd

,

smb

,

vncserver

,

arpwatch

,

named

,

snmpd

,

pxe

,

routed

,

mars nwe

,

ldap

,

kadmin

,

kprop

,

krb524

,

krb5kdc

,

gated

,

nscd

,

ypserv

,

ups

, and

irda

.

After all processes are killed,

init

looks into the same directory and finds start scripts for

kudzu

,

reconfig

,

ipchains

,

portmap

,

nfslock

,

autofs

,

random

,

netfs

,

apmd

,

identd

,

atd

,

pcmcia

,

sshd

,

rawdevices

,

xinetd

,

lpd

,

keytable

,

isdn

,

sendmail

,

gpm

,

canna

,

crond

,

FreeWnn

,

xfs

,

anacron

,

firstboot

,

rhnsd

, and

mdmonitor

.

The last thing the

init

program does is run any scripts located in

/etc/rc.d/rc.local

(see Sec 

tion 3.3 for more on customizing the

rc.local

file). At this point, the system is considered to be

operating at runlevel 5.