1. Linux+ Guide to Linux Certification, Second Edition Chapter 1 Introduction to Linux

2. Linux+ Guide to Linux Certification, 2e2 Objectives Understand the purpose of an operating system Outline the key features of the Linux operating system Describe the origins of the Linux operating system Identify the characteristics of various Linux distributions and where to find them Explain the common uses of Linux in industry today

3. Linux+ Guide to Linux Certification, 2e3 Operating Systems Computers have two fundamental components: –Hardware: Physical components inside a computer –Software: Set of instructions or programs that understand how to use the hardware of the computer in a meaningful way

4. Linux+ Guide to Linux Certification, 2e4 Operating Systems (continued) Hardware components include: –Processor (CPU) –Physical memory (RAM) –Hard disk, floppy disk, and CD-ROM drives –Sound and video cards –Circuit boards

5. Linux+ Guide to Linux Certification, 2e5 Operating Systems (continued) Two different types of programs are executed on a computer: –Applications –Operating system (OS) software Device Driver: Software containing instructions that the OS uses to control and interact with a specific type of computer hardware User Interface: An application program that allows the user to interact with the OS and other application programs

6. Linux+ Guide to Linux Certification, 2e6 Operating Systems (continued) Figure 1-1: The role of operating system software

7. Linux+ Guide to Linux Certification, 2e7 Operating Systems (continued) Graphical user interface (GUI): Component of an OS that provides a user-friendly interface System services: Applications that handle system- related tasks –Printing –Scheduling programs –Network access

8. Linux+ Guide to Linux Certification, 2e8 Operating Systems (continued) Figure 1-2: A Linux graphical user interface

9. Linux+ Guide to Linux Certification, 2e9 The Linux Operating System OS used to run a variety of applications on a variety of different hardware Has the ability to manage thousands of tasks at the same time Allows multiple users to access the system simultaneously –Multiuser and multitasking OS

10. Linux+ Guide to Linux Certification, 2e10 Versions of the Linux Operating System Core component is called the Linux kernel –Written almost entirely in the C programming language Software can be used to modify appearance of Linux, but the kernel is common to all Linux

11. Linux+ Guide to Linux Certification, 2e11 Identifying Kernel Versions Linux kernel versions are composed of: –Major number –Minor number If odd, referred to as a developmental kernel If even, referred to as a production kernel –Revision number

12. Linux+ Guide to Linux Certification, 2e12 Identifying Kernel Versions (continued) Table 1-1: Latest revisions of common Linux kernels

13. Linux+ Guide to Linux Certification, 2e13 Licensing Linux Open Source Software (OSS): Programs distributed and licensed so that the source code is available to anyone who wants to examine, utilize, or improve upon it –Format and structure of source code follows rules defined by the programming language in which it was written

14. Linux+ Guide to Linux Certification, 2e14 Licensing Linux (continued) Implications of OSS: –Developed very rapidly through widespread collaboration –Bugs (errors) are noted and promptly fixed –Features evolve quickly based on users’ needs –Perceived value of the software increases because it is based on usefulness, not on price

15. Linux+ Guide to Linux Certification, 2e15 Licensing Linux (continued) Table 1-2: Software types

16. Linux+ Guide to Linux Certification, 2e16 Types of Open Source Licenses GNU Public License (GPL): Stipulates that the source code of any software published under its license must be freely available Artistic license: OSS license allowing source code to be distributed freely, charged only at discretion of original author

17. Linux+ Guide to Linux Certification, 2e17 Types of Closed Source Licenses Most closed source software is sold commercially –e.g., Microsoft or Electronic Arts software Freeware: Distributed free of charge; source code is not available Shareware: Initially free, but requires payment after a period of time or usage

18. Linux+ Guide to Linux Certification, 2e18 Linux Advantages: Risk Reduction Changes in the market or customer needs may cause companies to change software frequently –Can be costly and time-consuming Support for closed source software may end –Vendor may go out of business –Software version may be retired OSS products offer the opportunity to maintain and change the source code

19. Linux+ Guide to Linux Certification, 2e19 Linux Advantages: Meeting Business Needs Common software available for Linux includes: –Scientific and engineering software –Software emulators –Web servers, Web browsers, and e-commerce suites –Desktop productivity software –Graphics manipulation software –Database software –Security software

20. Linux+ Guide to Linux Certification, 2e20 Linux Advantages: Stability and Security Customers using a closed source OS must rely on the OS vendor to fix any bugs –Waiting for a hot fix may take weeks or months Bugs and security loopholes in OSS programs can be identified and fixed quickly –Code is freely available and scrutinized by many developers

21. Linux+ Guide to Linux Certification, 2e21 Linux Advantages: Flexibility for Different Hardware Platforms Partial list of hardware platforms on which Linux can run: – Intel– M68K – Itanium– PA-RISC – Mainframe (S/390) – SPARC – Cirrus Logic ARM– Ultra-SPARC – DEC Alpha– PowerPC (Macintosh) – MIPS

22. Linux+ Guide to Linux Certification, 2e22 Linux Advantages: Ease of Customization Ability to control the inner workings of an OS –To use Linux as an Internet Web server, compile the kernel to include only the support needed to be an Internet Web server Results in a much smaller and faster kernel

23. Linux+ Guide to Linux Certification, 2e23 Linux Advantages: Ease of Obtaining Support Linux documentation can be found on the Internet –Frequently Asked Questions (FAQs) –HOWTO documents Linux Newsgroups Linux User Group (LUG): Open forum of Linux users who discuss and assist each other in using and modifying the Linux OS

24. Linux+ Guide to Linux Certification, 2e24 Linux Advantages: Cost Reduction Table 1-3: Calculating the total cost of ownership

25. Linux+ Guide to Linux Certification, 2e25 The History of Linux Figure 1-4: Timeline of UNIX and Linux development

26. Linux+ Guide to Linux Certification, 2e26 UNIX Evolved from Multiplexed Information and Computing Service (MULTICS) The first true multitasking, multiuser OS Written in the C programming language –Portable OS OS from which Linux originated

27. Linux+ Guide to Linux Certification, 2e27 UNIX (continued) Berkeley Software Distribution (BSD) –Version of the original UNIX source code Common flavors of UNIX today include: –Sun Microsystems’s Solaris –Hewlett-Packard’s HP-UX –IBM’s AIX UNIX

28. Linux+ Guide to Linux Certification, 2e28 The Hacker Culture Hacker: Someone wanting to expand their computing knowledge through experimentation Cracker: Someone who illegally uses computers for personal benefit or to cause damage GNU Project: Free OS project started by Richard Stallman

29. Linux+ Guide to Linux Certification, 2e29 Linux First developed by Linus Torvalds in 1991 –Published under the GNU license Linux kernel developed collaboratively and centrally managed –Linux is simply a by-product of OSS development

30. Linux+ Guide to Linux Certification, 2e30 Linux Distributions Red Hat and SuSE Distributions may appear different on the surface, but run the same kernel Most distributions ship with a GUI that can be further customized to suit needs of the user –Core component of this GUI is X Windows

31. Linux+ Guide to Linux Certification, 2e31 Linux Distributions (continued) GUI environment: X Windows in combination with a window manager and desktop environment Two competing GUI environments in Linux: –GNU Object Model Environment (GNOME) –Kommon Desktop Environment (KDE)

32. Linux+ Guide to Linux Certification, 2e32 Linux Distributions (continued) Figure 1-5: The GNOME Desktop

33. Linux+ Guide to Linux Certification, 2e33 Linux Distributions (continued) Package manager: Software system that installs and maintains software Tarball: Compressed archive of files containing scripts that install software to the correct location on the system

34. Linux+ Guide to Linux Certification, 2e34 Linux Distributions (continued) Table 1-4: Common Linux distributions

35. Linux+ Guide to Linux Certification, 2e35 Linux Distributions (continued) Table 1-4 (continued): Common Linux distributions

36. Linux+ Guide to Linux Certification, 2e36 Common Uses of Linux May be customized to provide services for a variety of companies in a variety of situations Workstation services: Services used on a local computer Server services: Services made available for other computers across a network

37. Linux+ Guide to Linux Certification, 2e37 Internet Servers: Mail Services Mail transfer agent (MTA): An e-mail server Mail delivery agent (MDA): Service that downloads e-mail from an MTA Mail user agent (MUA): Program that allows e-mail to be read by a user

38. Linux+ Guide to Linux Certification, 2e38 Internet Servers: Routing and FTP Services Routing: Provides interconnection between separate networks –Core service necessary for Internet to function –Linux provides support for routing and is easily customizable File Transfer Protocol (FTP) Services: Most common and efficient method for transferring files over the Internet

39. Linux+ Guide to Linux Certification, 2e39 Internet Servers: Firewalls and Proxy Services Firewall: Protects companies from outside intruders on the Internet –Linux has firewall support built into the kernel Proxy server: requests Internet resources such as Web sites and FTP sites on behalf of the computer inside the company

40. Linux+ Guide to Linux Certification, 2e40 Internet Servers: Web Services and News Services Web services: Web servers host information (text, pictures, music, binary data, and video) –Can also process programs known as Common Gateway Interface (CGI) scripts and provide secure connections News services: News servers allow users to post messages in forums called newsgroups –Most Web servers do not provide means for users to communicate

41. Linux+ Guide to Linux Certification, 2e41 Internet Servers: DNS Services Computers communicating on a network need to be uniquely identified –Each computer is assigned an Internet Protocol (IP) address Long string of numbers Allows computers to identify and reference each other Fully Qualified Domain Name (FQDN): Masks IP addresses with user-friendly names

42. Linux+ Guide to Linux Certification, 2e42 File and Print Servers Linux is well-suited for centrally sharing resources –More economical to share files and printers over a network –Inherently fast and light –A distribution specific to a certain task can be installed on the central server

43. Linux+ Guide to Linux Certification, 2e43 Application Servers Application server: Intermediary between a client computer and a database Database: Organized collection of data that is arranged into tables of related information Database Management Systems (DBMS): Set of programs designed for creation, modification, manipulation, maintenance, and access of information from databases

44. Linux+ Guide to Linux Certification, 2e44 Supercomputers Clustering: Combining several smaller computers to act as one large supercomputer –Beowulf clustering: Most common Linux method of clustering Scalability: Computers that can increase workload as number of processors increases

45. Linux+ Guide to Linux Certification, 2e45 Scientific/Engineering Workstation Scientific and engineering community often needs customized programs OSS programs can be used or modified –OSS software for physics, astrophysics, biophysics, biocomputation, data mining, etc.

46. Linux+ Guide to Linux Certification, 2e46 Office Workstation Workstation software designed for end users in office and home environments –Text editors and word processors –Graphics editing software –Desktop publishing software –Financial software –Office productivity suites

47. Linux+ Guide to Linux Certification, 2e47 Summary Linux is an OS Kernel and additional software are freely developed and improved upon by a large community of software developers Published under the GPL; is called Open Source Software (OSS) Companies find Linux a stable, low-risk, and flexible alternative to other OSs

48. Linux+ Guide to Linux Certification, 2e48 Summary (continued) Comes in different distributions, all having a common kernel, but packaged with different OSS applications Wide variety of documentation and resources exist: Internet Web sites, HOWTOs, FAQs, newsgroups, and LUGs Extremely versatile OS that provides a wide range of workstation and server services