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The System Boot Process

(Chap. 13)

ICE System Consultant 2nd

2002 8 7

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Objectives

Describe the four phases of the boot processModify the kernels configuration file

Describe the eight run levels

Explain the purpose of the /etc/inittab file

Describe the steps in the init process to bring a system to

multi-user mode

List the directories that hold the run control scripts used to

stop and start system processes and servicesDescribe the steps to add a new run control script

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Run Levels

%who r command Shows current run level

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The Boot Process

Power onPOST (in PROM)

PROM parameter (boot-device)

Read the 1 ~ 15 sector (boot block)

Ufsboot (secondary booting program) loading to memory

Kernel load

Kernel module load

Initialize the kernel (read the /etc/system file)

/etc/init process

Read the /etc/inittab file

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The Boot Process (Cont.)

Boot PROM phasePOST to boot block

Boot programs phase

Ufsboot to load kernel

Kernel initialize phase

Kernel module load to reading /etc/system file

Init phase

Kernel starts /etc/init to rc script

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/etc/system File

ModdirSets the search path for default loadable kernel modules

Root device and root filesystem configurationSets the root file system type to the listed value

Default value is ufsSets the root device (physical name)

ForceloadForces the kernel modules to be loaded during kernel

initializationSetChanges kernel parameters to modify the operation of the

system

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/etc/inittab File

To change run levelWhen the system boots, the init daemon starts processes

by reading information from the /etc/inittab file

Include

Systems default run levelwhat process to start, monitor, or restart if terminated

What actions to take for new run level

Form

Id : identifier for the entryRstate : run level for this entry

Action : how the process is to be treated

Process : execute

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Run Control Script

/sbin directoryEach run level has an associated rc script located in the /sbin

directory

Rc0, rc1, rc2, rc3, rc5, rc6, rcS

Executed by init to set up variables

/etc/rc#.d directoryScript that start and stop system processes for that run level

Start with S- file : start the script with current run level

Start with K- file : kill the process with current run level

/etc/init.dRun control scripts

Hard-linked to /etc/rc#.d directory

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Creating a New Run Control Script

rc_test file#!/bin/sh

#test rc script

case $1 in

start) /usr/bin/audioplay /usr/demo/SOUND/sounds/ring.au

/bin/banner rc_start

;;

stop) /usr/bin/audioplay /usr/demo/SOUND/sounds/bark.au

/bin/banner rc_stop

;;

esac

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Creating a New Run Control Script (Cont.)

#vi /etc/init.d/rc_test#chmod +x rc_test

#/etc/init.d/rc_test stop

#/etc/init.d/rc_test start

#ln rc_test /etc/rc3.d/S100rc_test

#ln rc_test /etc/rc0.d/K100rc_test

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System Shutdown Procedures

#halt = init 0 : ok go command#reboot = init 6

#poweroff = init 5 : power off

#shutdown = init sNo power off

Kill all the processes & change the run level

Options

-y : shutdown right now -g 300 : shutdown after 300 second

-i 0 ~ s : change the run level