1. Introduction to Linux Environment Dr.S.Siva Kumari Mrs.S.Siva Ranjani Avinashilingam University

2. Overview What is Unix/Linux? History of Linux Architecture of Linux Features of Linux Benefits of Linux Variants of Linux Application areas

3. Before Linux In 80’s, Microsoft’s DOS was the dominated OS for PC Apple MAC was better, but expensive UNIX was much better, but much, much more expensive. Only for minicomputer for commercial applications People was looking for a UNIX based system, which is cheaper and can run on PC Both DOS, MAC and UNIX were proprietary, i.e., the source code of their kernel is protected No modification is possible without paying high license fees

4. What is Unix? A multi-task and multi-user Operating System Developed in 1969 at AT&T’s Bell Labs by –Ken Thompson (Unix) –Dennis Ritchie (C) –Douglas Mcllroy (Pipes - Do one thing, do it well)

5. Unix Design Principles Make each program do one thing well. Expect the output of each program to become the input to another program. Design and build software to be tried early. Use tools to lighten a programming task. Everything is a file. Configuration files are text

6. Beginning of Linux – A famous professor Andrew Tanenbaum developed Minix, a simplified version of UNIX that runs on PC – Minix is for class teaching only. No intention for commercial use – In Sept 1991, Linus Torvalds, a second year student of Computer Science at the University of Helsinki, developed the preliminary kernel of Linux, known as Linux version 0.0.1

7. Linux Today – Linux has been used for many computing platforms – PC, PDA, Supercomputer,… – Not only character user interface but graphical user interface is available – Commercial vendors moved in Linux itself to provide freely distributed code. They make their money by compiling up various software and gathering them in a distributable format – Red Hat, Slackware, etc

8. What is Linux? A clone of Unix Developed in 1991 by Linus Torvalds Inspired by and replacement of Minix Linus' Minix became Linux Consist of –Linux Kernel –GNU (GNU is Not Unix) Software –Software Package management –Others

9. Comparison between Linux and Unix FeaturesLinuxUnix Amount of hard disk space required 150MB500 MB Licensing(General Public Licensing) GPL Paid Licensing VariantsRed Hat,SuSE, Debian. Ultrix, Sun Solaris

10. GNU and the GPL GNU project was started in the 1983 by Richard Stallman with the goal of creating a free software operating system: The GNU tools are released under the GPL, the General Public License.

11. This license guarantees that free software remains free. Under this license, a user of software has the following: The freedom to run the program for any purpose The freedom to study the program and adapt the source code to their needs The freedom to redistribute copies of the program The freedom to improve the program and release your improvements to the public

12. Architecture of Linux Linux architecture consists of three software components as follows: 1. Kernel 2.Shell 3.Utilities

13. Kernel It is the core of the Linux OS Provides services for all other components of OS Controls the resources of a computer by allocating them to different Linux users and tasks. Interacts directly with the hardware but however does not interact directly with the user. Users can use an interactive program called shell to interact with the hardware.

14. Shell It is a user interface that helps the user to interact with the Linux OS. Provides services(viewing a file and create or removing a directory or a file) requested by Linux Users. Hides the complex hardware details from the Linux users. Used as a command line interface to run commands and programs.

15. Utilities Utilities are collections of programs that provide processing requirements such as searching a word in a file and viewing access permissions of files. Utilities are the programs that are invoked through the shell of the Linux OS.

16. Features of Linux Multiprogramming :Allows many programs to be executed simultaneously by different users. Time sharing:Allows multiple programs to share CPU time for their execution Multitasking: Enables execution of multiple tasks simultaneously. Virtual memory:To optimize the use of the resources.Linux makes a portion of the harddisk available for use as VM to keep frequently used programs and data.

17. Contd., Shared Libraries: Applications can use the functions in the shared Library to save harddisk space and memory.No need to write the code separately for each application. Network Information Service(NIS):NIS server maintains a central database of account information that is used for account authentification. Features such as Cron scheduler, Office suite, data backup and web server

18. What are the benefits of Linux? A modern, very stable, multi-user, multitasking environment. Advanced graphical user interface. Reliability: Linux OS enables us to work consistently with Linux server without reporting any OS failures. Backward compatibility: Feature for providing support for existing hardware. Easy upgrade and installation process.

19. Low cost: Most Packages with it are available free of cost. For installing Linux speed of processor and RAM required are very minimal and hence hardware cost also goes down. Freedom from viruses. Linux has no viruses because it is too secured operating system for the viruses to spread. Linux offers excellent security features and hence many internet service providers are replacing their current Os with Linux. Supports Large number of users working simultaneously That is why Linux is used in the organizations where the number of users are Large. Offers Excellent platform for many development Languages such as C,C++,Java,Python,PHP.

20. Future of Linux Growing and growing… Linus made the source code open to public. At the end of 1992 there were about a hundred Linux developers. Next year there were 1000. And the numbers multiplied every year. Recent estimates say about 29 million people use Linux worldwide.

21. Variants of Linux Red Hat Linux : One of the original Linux distribution.Red Hat Linux The commercial, nonfree version is Red Hat Enterprise Linux,Red Hat Enterprise Linux Free version: Fedora Project.Fedora Project Debian GNU/Linux : A free software distribution. Popular for use on servers. However, Debian is not what many would consider a distribution for beginners, as it's not designed with ease of use in mind.Debian GNU/Linux SuSE Linux : SuSE was recently purchased by Novell. This distribution is primarily available for pay because it contains many commercial programs, although there's a stripped-down free version that you can download.SuSE Linux Mandrake Linux : Mandrake is perhaps strongest on the desktop. Originally based off of Red Hat Linux.Mandrake Linux Gentoo Linux : Gentoo is a specialty distribution meant for programmers.Gentoo Linux

22. Application areas As server OS In Embedded system In E-Commerce

23. Linux as a server operating system The usage and commercialization of Linux has increased because it is a powerful server operating system. The modifications in the open source code of Linux enable you to run windows applications on the Linux operating system. This means you need not purchase windows to run its applications on Linux. The Linux provides server features. For example, the Linux kernel consists of networking and security features. Linux is widely used by internet service providers(ISPs) as a server operating system.

24. The various server features provided by Linux are: Provides the networking standard called IP networking, on which internet is built. Supports several LAN interfaces or LAN cards. Supports ISDN, dial - up networking, and wide area network(WAN) systems. Provides router features, such as packet forwarding. Acts as a gateway for a network that is connected to Internet. Provides firewall features, such as packet filtering and network traffic accounting.

25. Linux in Embedded Systems Linux is suitable for embedded systems because of its availability and scalability. An embedded system is a combination of computer hardware and software that has either predefined or programmable capabilities and is designed for specific type of application devices, such as automobiles, household appliances and airplanes. The open source code of Linux is available to the developers for modifying according to their requirements. For examples, if you do not require the file sharing components of Linux, you can remove that portion of Linux and reduce the memory requirements for your computer.

26. Contd., Embedded systems in medical applications require considerable stability, which can be obtained by using Linux. If you use Linux in embedded systems, you need to spend less money for support as compared to conventional embedded operating systems. The open source licensing of Linux reduces development costs and product costs for developers of embedded systems. This licensing also provides opportunity to the developers of embedded systems to quickly launch their products in the market.

27. Linux in E - Commerce Applications The E - Commerce servers usually use Sun’s Solaris or Windows NT operating systems for e- commerce applications. As the initial license fee for these operating systems is high, a substantial amount of money is to be invested. Linux is a good alternative for these operating systems as it has low cost, high security and is easy to maintain.

28. Contd., The Linux-based operations of the business develop along with the e-commerce applications. Linux has gained acceptance as an enterprise operating system because of its various features, such as high security and reliability. It is used for e-commerce applications even by large organizations.