linux systm architcture

8/12/2019 Linux Systm Architcture

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Linux System Architecture

By : Amir Hossein [email protected]


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Contents !hat is "ernel# "ernel Architecture $vervie%

User Space "ernel Space

"ernel &unctional $vervie% &ile System Process 'ana(ement )evice )river 'emory 'ana(ement *et%or+in(


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What is Kernel ?

'o-ules or subsystems that provi-ethe operatin( system /unctions.

The 0ore o/ $S t is %ritten in 0


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Kernel Architecture Overview


)ata &lo% Bet%een User Space an-"ernel Space


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User Space The User Space is the space in memory

%here user processes run. This memory is above the "ernel.

t inclu-es the rest o/ available memory.

This Space is protecte-. The system prevents one process /rom

inter/erin( %ith another process. $nly "ernel processes can access a user

process


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Kernel Space The "ernel Space is the space in

memory %here all +ernel services areprovi-e- via +ernel processes.

The user has access to it only throu(hthe system call. A user process becomes a +ernel process

%hen it executes a system call.


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System Call

User Space an- "ernel Space are in-i//erent spaces.

!hen a System 0all is execute-7 thear(uments to the call are passe- /rom

User Space to "ernel Space.


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User Space and Kernel SpaceRelationship

UserProcess

Library Routine

Syscall ispatch

KernelService

UserSpaceKernelSpace

ata!low


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Kernel !unctional Overview

&ile System Process 'ana(ement

)evice )river 'emory 'ana(ement *et%or+in(


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Kernel !unctional Overview


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!unctional Layer "Architectural Layer


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!ile System t is responsible /or storin( in/ormation

on -is+ an- retrievin( an- up-atin( thisin/ormation.

The &ile System is accesse- throu(hsystem calls such as : open7 rea-7 %rite7

;xample : &AT147 &AT,7 *T&S ext7 ext,


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!ile System #Cont$%

>

>bin >etc >-ev >usr >home >root

ls pin( A B

-ata.txt pic.(i/


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!ile System Structure

Boot Bloc+ : in/ormation nee-s to boot thesystem Super Bloc+ : &ile System Speci/ications

Si?e

'ax. number o/ /iles&ree bloc+s

&ree ino-es

ino-e List Bloc+ List :The /iles -ata

&oot&loc'

Super&loc'

inodeList

&loc'List


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(node ;ach /ile has an ino-e structure that is

i-enti/ie- by an inumber. The ino-e contains the in/ormation

reuire- to access the /ile. t -oesnt contain /ile name.


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(node #Cont$%


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irectories

!ile)ame

inode )umber


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Process *ana+ement#Cont$%

n the Unix system process 97 calle- thes%apper7 is al%ays assi(ne- to the process an-0PU sche-uler.

t mana(es the complete operation o/ processsche-ulin( an- s%appin(.

Process 9 is create as a part o/ system bootup. ;very other process in the system is create as

the result o/ a /or+system call. The /or+ system call splits a process into t%o

processes


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Process *ana+ement#cont$%

;ach process is represente- by a tas+struct-ata structure. t contains the speci/ications o/ each process such

as: State Sche-ulin( in/ormation -enti/ier

The tas+vectoris an array o/ pointers to everytas+struct -ata structure in the system. This means that the maximum number o/ processes

in the system is limite- by the si?e o/ the tas+ vector


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,ype o- Processes Cunnin(

The process is either runnin( or it is rea-y torun.

!aitin( The process is %aitin( /or an event or /or a

resource.

Stoppe-

The process has been stoppe-7 usually byreceivin( a si(nal.

Dombie This is a halte- process %hich7 /or some

reason7 still has a tas+struct -ata structure inthe tas+ vector.


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evice river Associate- %ith each physical -evice or

virtual -evice is a piece o/ co-e7 calle--evice -river7 %hich mana(e the -evice

har-%are. The main /unctions o/ -evice -river:

Settin( up har-%are on initiali?ation. Brin(in( the associate- -evices into an- out

o/ services. Ceceivin( -ata /rom the har-%are an-

passin( it bac+ to the +ernel. Sen-in( -ata /rom the +ernel to the -evice.

)etectin( an- han-lin( -evice errors.


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*a.or )umber and *inor)umber

'aEor *umber The maEor number i-enti/ies the -river

associate- %ith the -evice.

'inor *umber The minor number is use- only by the -river

speci/ie- by the maEor numberF other parts o/the +ernel -onGt use it.

t is common /or a -river to control several-evices7 the minor number provi-es a %ay/or the -river to -i//erentiate amon( them.


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evice river #Cont$%


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User Space

"ernel Space "ernel &unctional $vervie%

&ile System Process 'ana(ement )evice )river 'emory 'ana(ement *et%or+in(


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*emory *ana+ement Physical memory is -ivi-e- into

se(ments o/ eual si?e7 calle- pa(es. Type o/ memory:

Physical memory irtual memory S%ap memory


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/irtual and swap memory

S%ap t is a con/i(urable partition on -is+ treate- in a

manner similar to memory.

irtual memory Processes s%appin( in an- out o/ memory on a

recurrin( basis /ra(ment physical memory. t is impossible to (uarantee that exactly the same

physical memory bloc+s %ill be available to a speci/icprocess.

irtual a--ress space solves this problem byassi(nin( conti(uous virtual memory bloc+s to aprocess.

These bloc+s are mappe- to physical memory %hena process is s%ap in7 an- to s%ap -evice memory%hen the process is s%appe- out.


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Physical and /irtual memory


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User Space

"ernel Space "ernel &unctional $vervie%

&ile System Process 'ana(ement )evice )river 'emory 'ana(ement *et%or+in(


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)etwor'in+ The /irst inte(rate- communication

capability in Unix %as -evelope- /orBer+eley Unix 2.bs- as the soc+ets

implementation. Soc+ets provi-e a pro(rammin(

inter/ace /or net%or+in(.


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linux systm architcture

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