overview of linux kernel

8/7/2019 Overview of Linux Kernel

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Overview of Linux Kernel

Linux is a type of UNIX


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Free Software and Open Source

Linux Most successful for Open sourcesoftware

Open source software source code isfreely available such that anyone canmodify, read and redistribute

Open source licensed under GNU General

Public License(GPL) version 2(Closed source software distributed only in

binary form)


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Linux Distributions

Linux Distribution = Linux Kernel + tools +

Window Managers + Applications

System programs of Linux are developedby Free Software Foundation (FSF) GNU

project.

Organizes the tools and applications into

groups of header and executable files.

Grouping packages used for compilation


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Linux Distributions are:

DebianBetter package mgmt system

Initial installation is difficult

Red Hat/Fedora

Red hat Enterprise-Bussiness,Govt and Industry,stable,in America

Fedora Core- For Individual Users,less stable

Mandriva

Easier to install and system configuration,setup

SUSE

business,govt,industry and individual users

Its installation and administration tool Yast2,in Europe Gentoo

New Linux Distribution,all the packages are compiled for specificconfiguration of machine

Yellow Dog

PPC based Linux Distribution(Power PC processor based)


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Linux Operating System

Kernel Space+User Space

Kernel is all hardware resources

Outermost layer of procedures- Kernel

Hardware management functionalities-Kernelspace

User associates with OS by User space

User space does not access the Kernel directly

but by system calls Within the Kernel, system call procedures call onto other procedures not in user space for finerfunctionality


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Linux Operating System

The subset of procedures not visible to user

space is made up in part by functions from

individual device drivers

Device Drivers - well defined interface fns for-system call and kernel

Figure: LINUX ARCHITECTURE

Application Application Application

Application

System calls

Device driver Device driver Device driver Device driver


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Overview of Linux Kernel

Kernel Organization-Linux supports numerousarchitectures

runs on many types of processors

Like alpha,arm,i386,ia64,ppc,ppc64 etc Linux source code supports all abovearchitectures

Most source code - C, assembly language andhardware independent

Machine dependent portion - boot strapping,exception vector handling ,address translation,device I/O-system calls


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Kernel Interface

Various components (subsystems) of Kernel are

File system

Processes Scheduler

Device drivers


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User Interface

Users communicate with system-Programs

User logs in-thru a terminal or a virtual terminal

In Linux a program is called Mingetty forVirtual terminaloragetty forserial terminals monitors the inactiveterminal waiting for notify who is logged on

To Log in EnterAccount name and password

called login the system

Getty program -all account names and password

authentication allows them to system if there is a match or terminates if

no match are all respawned if once terminated


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User Interface

Login successfully- User program executes aShell

A shell is a command Interpreterand consists ofa listening process

Listening Process interprets and executes therequests typed

Shell displays a Command Prompt

User interacts with the system thru syntaxdefined by shell

Programs a user can call- Exe files

Execution of requests-shell spawning


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User Identification

User Id-UID to validate users permission

with respect to file accesses

User log in to home directory User is a member of one or more group

which has a group-id(GID)

A file is associated with UID or GID


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Files and File System

File system provides a method for storage andorganization of data

Linux supports file concept as a device independentsequence of bytes

User can access a file regardless of device like harddisk,cd,floppy etc

Files are grouped in-directories

File structure is a hierachical tree- called file hierarchy

Top most node in which all files and directories arestored- root(identified by /)

File system is in hard disc partition


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Directories Files and Path names

Every file in a tree has path name indicates

name and location

A file has directory in which it belongs called

current working directory or directory user islocated in is called relative pathname

A path name taken from root of the system-

Absolute path name

Eg:/home/rose/src/file.c-Absolute path name

Eg:src/file.c-relative path name


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Hierarchical file Structure

/

Bin Boot

anna rose sophi

src

file.c


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overview of linux kernel

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