LPI 101 Ch09 Startup and Shutdown

8/9/2019 LPI 101 Ch09 Startup and Shutdown

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SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102

Chapter 9

System Startup and Shutdown


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Objectives

Define and explain bootstrap procedure

Explain single and multi-user run levels

Identify and configure system startup files

Perform a clean shutdown procedure

Explain and define the maintainance mode


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Standard Boot Process (LILO)

System load the Linux bootstrap from default boot device,

LILO (GRUB), which resides in Master Boot Record of

hard drive

The

bootstrap program has abi

li

ty to boot Li

nux

to si

ngle-

user or multi-user mode

After the bootstrap has loaded the kernel ( stored in the

/boot or / partition ) into memory, it relinquishes control to

this system


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Standard Boot Process (LILO)

The Linux system initializes physical devices, virtual

memory controller, and its internal control tables for

processes, files, ..

The

i

ni

t proce

ssi

s starte

d andi

t starts all othe

r use

rprocesses

Before handing control over init, the kernel will create any

other kernel threads


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Boot Problems

Sometimes, lilo will not able to boot the system, it prints the

letters LILO on screen. The problems: diskcorrupted, the

information on diskgeometry is incorrect, or since the new

kernel imageis installed

Troubleshooting: boot the system from bootable CD or

floppy and try to repair disk problems or correct the

/etc/lilo.conf


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Manual Boot

There are times when lilo has loaded the kernel but the kernel

does NOT work properly because some of hardware can not

befound,Its possible topass configuration to the kernel

through lilo at lilo command line when booting:


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Manual Boot

List of someimportant boot prompt arguments :

root=/dev/hda1 Tell the kernel which device to be mounted asroot file system

ramdisk_size=2MB Define maximum of ramdisk (up to 4MB )single This actually is a parameter passed to init,

causes the system to boot in single-usermode

mem=192MB Tell the kernel amount ofmemory ( RAM size )

aha1542=0x334 Set the I/O port address for SCSI Interface Card

hdc=cdrom Specifies the third disk deviceis a CD-ROM

Instead of typing them at each reboot, these arguments can beincluded into the lilo.conf :

append=hdc=cdrom


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Manual Boot

Moreinformation about boot prompt and arguments can be

found at:

http://www.tldp.org/HOWTO/BootPrompt-HOWTO.html

Refers to man 5 lilo.conffor a detailed information aboutarguments


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Startup Flow Control

It used to run Linux system at level 3


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Run Levels

Runlevel 0/etc/rc.d/rc0.d

Shutdown mode. Tasks: killing all processesand unmounting file systems


Single-user mode, generally used by systemadministrator when doingmaintenance/recovery of the system


Multi-user mode, some network services arenot started : NFS,


Multi-user mode, all network services arestarted


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Run Levels


User defined run level


Multi-user X11 mode. All services that arestarted in run level 3 are generally started


Reboot runlevel.

Runlevel s/S/etc/rc.d/rcS.d

Single-user mode.

Runlevel a/b/c Pseudo states. (rarely used)


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Run Levels Using

Use /sbin/runlevel to get current run level

How to start X window ?

RedHat and TurboLinux : # init 5

Debian : # init 2 SuSE and Caldera: # init 3

Slackware : # init 4

Re

boot : #i

ni

t 6 Shutdown : # init 0

To manual set default run level at boot time, open

/etc/inittab and lookfor this line : id:5:initdefault:


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Structure of/etc/inittab

Each line has 4 fields seperated by colons:

id:level:action:command

id Uniqueidentifier for line (up to 4 alphanumericcharacters)

level Run level(s) to activate processs

action Keyword for how to run processcommand Full path name and parameters of command to

beexecuted


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Structure of/etc/inittab

The main inittab action keywords are:

Off Do not run this command. Used to retain an entry butto disableit.

wait Run command and wait for completion

once Run command but do not wait. Daemons processesare often started this way

respawn Run command; If process exists, then rerun it. Usedfor commands that have to start again aftercompletion, like getty and ttymon

sysinit Run command at first init

boot Run command at boot time but do not wait

bootwait Like boot but wait for completion

initdefault Defines default boot level


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/etc/inittab

# more /etc/inittab

id:3:initdefault:

#System initialization

si::sysinit:/etc/rc.d/rc.sysinit

l0:0:wait:/etc/rc.d/rc 0








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Run Command Scripts

The run commands scripts are kept under /etc/rc.d/ and areinitiated by init with directions from /etc/inittab

The script called rc itself runs startup programs in sub-

di

re

ctorie

s unde

r /e

tc/rc.d/ rc 0 looks in /etc/rc.d/rc0.d for runlevel 0

rc 1 looks in /etc/rc.d/rc1.d for runlevel 1

rc 2 looks in /etc/rc.d/rc2.d for runlevel 2

etc


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Run Command Scripts

These startup programs are symbolic links to the actualscripts in the /etc/init.d/

The startup link names areformatted:firstcharacter isS

(starte

d) orK(ki

lle

d or stoppe

d), the

next two digitsi

de

ntif

ytheorderthat scripts areexecuted by rc program


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Changing Run Levels

Useinit command to change between run levels. Syntax :

init

Examples :

# init 0 Shutdown system

# init 6 Reboot system

# init 3 Change to runlevel 3, multi-user text mode

# init 5 Change to runlevel 5, multi-user X11 mode


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Shuting Down

Use shutdown commansd. It differs from init 0 whenallowing to specify time to exit, warn users what happens,

Make sure that you follow the proper shutdown procedure.

Do NOT simply shut off the power

# shutdown Default system shutdown (run level1)

# shutdown r now R eboot the system now (run level6)

# shutdown h 2:00 Halt the system at 2:00AM (runlevel 0)


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Maintenance Mode

When the system doesnt work because problems. Thesimplest and best solution is to shut down the system to

maintenance mode (run level 1) or reboot the system to

single-user mode (run level S) and try to fix problems


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LPI 101 Ch09 Startup and Shutdown

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