Linux 301

8/13/2019 Linux 301

1/17

16-02-2014Dr. Vaibhav Bansal 1

MCA301 : LINUX PROGRAMMING

OBJECTIVES:A comprehensive overview of the Linux operating system

along withShell commands and shell scripting

Implementation of Linux System programmes through GCC

compiler.

Understanding of basic concept of Socket programming

(TCP and UDP)

Tecnia Institute of Advanced

Studies

8/13/2019 Linux 301

2/17

Events leading to creation

Unix : The Unixoperating system was conceivedand implemented by Ken Thompsonand DennisRitchie(both of AT&T Bell Laboratories) in 1969

and first released in 1970. In 1983, Richard Stallman started the GNU

projectwith the goal of creating a freeUNIX-likeoperating system (GNU: GNUis a recursive acronymfor"GNU's Not Unix!",chosen because GNU's design is Unix-like,but differs from Unix by being free software and containingno Unixcode)

16-02-2014Dr. Vaibhav Bansal 2

8/13/2019 Linux 301

3/17

Events leading to creation Another free operating system project, initially released

in 1977, was the Berkeley Software Distribution (BSD).

This was developed by UC Berkeleyfrom the 6th editionof Unixfrom AT&T.

In 1991, in Helsinki (University), Linus Torvalds began a

project that later became the Linux kernel. It was initially a terminal emulator(In computing, an emulatoris

hardware or software or both that duplicates (or emulates) thefunctions of one computer system (the guest) in anothercomputer system (the host), different from the first one, so thatthe emulated behaviour closely resembles the behavior of the real

system (the guest)). Development was done on MINIX using the GNU C compiler,

which is still the main choice for compiling Linux today(although the code can be built with other compilers, such asthe Intel C Compiler).

16-02-2014Dr. Vaibhav Bansal 3

8/13/2019 Linux 301

4/17

What is Linux?

History The History of Linux began in 1991 with the

commencement of a personal project by a Finnishstudent,Linus Torvalds, to create a new free operating systemkernel.

Torvalds first published the Linux kernel under itsown licence, which had a restriction on commercialactivity. The software to use with the kernelwas software

developed as part of the GNU projectlicensed under the

GNU General Public License, a free softwarelicense. Thefirst release of the Linux kernel, Linux 0.01, included abinary of GNU's Bash shell.

16-02-2014Dr. Vaibhav Bansal 4

8/13/2019 Linux 301

5/17

Linux Linux is a Unix-like computer operating system

assembled under the model of free and open sourcesoftwaredevelopment and distribution.

The defining component of Linux is the Linux kernelan operating system kernel first released on 5

October 1991, by Linus Torvalds.

Since the C compiler that builds Linux and the mainsupporting user space system tools and librariesoriginated in the GNU Project, initiated in 1983 byRichard Stallman, the Free Software Foundationprefers the name GNU/Linux.

16-02-2014Dr. Vaibhav Bansal 5

8/13/2019 Linux 301

6/17

Where is Linux Used?

75% of respondents were already using Linuxand another 14% were evaluating it

43% of all web sites use Linux servers runningthe Apache Web server

16-02-2014Dr. Vaibhav Bansal 6

8/13/2019 Linux 301

7/17

How is Linux Used?

Personal Workstation

File and Print Server

Internet Service Provider Three-tier Client/Server

Turnkey System

16-02-2014Dr. Vaibhav Bansal 7

8/13/2019 Linux 301

8/17

Linux Features

Multitasking:several programs running at the same time. Multiuser: several users on the same machine at the same

time (and no two-user licenses!).

Multiplatform:runs on many different CPUs, not just Intel.

Multiprocessor/Multithreading: it has native kernelsupport for multiple independent threads of control within asingle process memory space.

It has memory protection between processes, so that oneprogram can't bring the whole system down.

Demand loads executables: Linux only reads from disk thoseparts of a program that are actually used.

16-02-2014Dr. Vaibhav Bansal 8

8/13/2019 Linux 301

9/17

Linux Features Shared copy-on-write pages among executables. This means

that multiple process can use the same memory to run in.When one tries to write to that memory, that page (4KBpiece of memory) is copied somewhere else. Copy-on-writehas two benefits: increasing speed and decreasing memoryuse.

Virtual memory using paging (not swapping wholeprocesses) to disk: to a separate partition or a file in the filesystem, or both, with the possibility of adding moreswapping areas during runtime (yes, they're still called

swapping areas). A total of 16 of these 128 MB (2GB in recentkernels) swapping areas can be used at the same time, for atheoretical total of 2 GB of useable swap space. It is simpleto increase this if necessary, by changing a few lines of

source code. 16-02-2014Dr. Vaibhav Bansal 9

8/13/2019 Linux 301

10/17

Linux Features

A unified memory pool for user programs and disk cache, so that all freememory can be used for caching, and the cache can be reduced when runninglarge programs.

All source code is available, including the whole kernel and all drivers, thedevelopment tools and all user programs; also, all of it is freely distributable.Plenty of commercial programs are being provided for Linux without source, but

everything that has been free, including the entire base operating system, is stillfree.

Multiple virtual consoles: several independent login sessions through theconsole, you switch by pressing a hot-key combination (not dependent on videohardware). These are dynamically allocated; you can use up to 64.

Supports several common file systems, including minix, Xenix, and all thecommon system V file systems, and has an advanced file system of its own,which offers file systems of up to 4 TB, and names up to 255 characters long.

Many networking protocols: the base protocols available in the latestdevelopment kernels include TCP, IPv4, IPv6, AX.25, X.25, IPX, DDP (AppleTalk),Netrom, and others. Stable network protocols included in the stable kernelscurrently include TCP, IPv4, IPX, DDP, and AX.25.

16-02-2014Dr. Vaibhav Bansal 10

8/13/2019 Linux 301

11/17

Using Linux on Personal Computers

Linux kernel for free

Kernel is central component

Kernel can be customized to users needs

16-02-2014Dr. Vaibhav Bansal 11

8/13/2019 Linux 301

12/17

Linux Distributions

Corel Linux

Debian GNU/Linux

OpenLinux (Caldera) Red Hat

Slackware

SuSE TurboLinux

16-02-2014Dr. Vaibhav Bansal 12

8/13/2019 Linux 301

13/17

13

API

AUI

Kernel

Computer Hardware

System call interface

Applications: Compilers, word processors, X-based GUI

BIOS

LINUX Shell: Bourne Again (bash), TC, Z, etc.

Language libraries

Device Drives

File managementMemorymanagement

ProcessManagement

Architecture

16-02-2014Dr. Vaibhav Bansal

8/13/2019 Linux 301

14/17

14

Kernel The part of an OS where the real work is done

System call interface

Comprise a set of functions (often known as API) that can be used bythe applications and library routines to use the services provided by the

kernel

Application Users Interface Interface between the kernel and user Allow user to make commands to the system

Divided into text based and graphical based

Architecture

16-02-2014Dr. Vaibhav Bansal

8/13/2019 Linux 301

15/17

15

File Management Control the creation, removal of files and provide directory

maintenance For a multiuser system, every user have its own right to access

files and directories

Process Management For a multitask system, multiple programs can be executed

simultaneously in the system

When a program starts to execute, it becomes a process

The same program executing at two different times will become

two different processes

Kernel manages processes in terms of creating, suspending,

and terminating them.

A process is protected from other processes and can

communicate with the others

Architecture

16-02-2014Dr. Vaibhav Bansal

8/13/2019 Linux 301

16/17

16

Memory management Memory in a computer is divided into main memory(RAM) and secondarystorage(usually refer to hard disk)

Memory is small in capacity but fast in speed, and hard disk is vice versa

Data that are not currently used should be saved to hard disk first, while data

that are urgently needed should be retrieved and stored in RAM

The mechanism is referred as memory management

Device drivers Interfaces between the kernel and the BIOS

Different device has different driver

Architecture

16-02-2014Dr. Vaibhav Bansal

8/13/2019 Linux 301

17/17

16-02-2014Dr. Vaibhav Bansal 17