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Linux+ Guide to Linux Certification, Third Edition

This chapter provides an overview of the Linux operating system, including its key features, origins, and various distributions. It also explores the common uses of Linux in industry and introduces the components of an operating system.

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Linux+ Guide to Linux Certification, Third Edition

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

  2. 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 Linux+ Guide to Linux Certification, 3e

  3. Operating Systems • Computers have two fundamental components: • Hardware: physical components inside a computer • Software: set of instructions or programs that allow hardware components to manipulate data Linux+ Guide to Linux Certification, 3e

  4. Operating Systems (continued) • Hardware components include: • Processor (CPU) • Physical memory (RAM) • Hard disk drives • Sound cards • Video cards • Circuit boards Linux+ Guide to Linux Certification, 3e

  5. Operating Systems (continued) • Two different types of programs are executed on a computer: • Applications: programs designed for a specific use and with which a user interacts • Operating system (OS) software: software components used to control the hardware of the computer Linux+ Guide to Linux Certification, 3e

  6. Operating Systems (continued) • 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 • Can be a command line prompt or a graphical user interface (GUI) Linux+ Guide to Linux Certification, 3e

  7. Operating Systems (continued) Figure 1-1: The role of operating system software Linux+ Guide to Linux Certification, 3e

  8. Operating Systems (continued) • Graphical user interface (GUI): component of an OS that the user can interact with using the keyboard or the mouse • System services: applications that handle system-related tasks • Printing • Scheduling programs • Gainingnetwork access Linux+ Guide to Linux Certification, 3e

  9. Operating Systems (continued) Figure 1-2: A Linux graphical user interface Linux+ Guide to Linux Certification, 3e

  10. The Linux Operating System • OS used to run a variety of applications on a variety of different hardware components • Multiuser and multitasking OS • Has the ability to manage thousands of tasks at the same time • Allows multiple users to access the system simultaneously Linux+ Guide to Linux Certification, 3e

  11. 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 • Important to understand Linux kernel version numbers to decide which version is appropriate for user needs • Good understanding of system hardware is important in deciding which kernel version to use Linux+ Guide to Linux Certification, 3e

  12. Identifying Kernel Versions • Linux kernel versions are composed of: • Major number • Minor number • If odd, referred to as a developmental kernel: a kernel which is not fully tested and with implied instability • If even, referred to as a production kernel: a kernel that has been thoroughly tested and is declared to be stable • Revision number Linux+ Guide to Linux Certification, 3e

  13. Table 1-1: Latest revisions of common Linux kernels Linux+ Guide to Linux Certification, 3e

  14. Licensing Linux • Open Source Software (OSS): programs distributed and licensed so that the source code is available, free of charge, 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 Linux+ Guide to Linux Certification, 3e

  15. 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 Linux+ Guide to Linux Certification, 3e

  16. Licensing Linux (continued) Table 1-2: Software types Linux+ Guide to Linux Certification, 3e

  17. 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 • Users who modify the source code must also redistribute the modified code freely • Artistic license: OSS license allowing source code to be distributed freely, changed only at discretion of original author Linux+ Guide to Linux Certification, 3e

  18. Types of Closed Source Licenses • Most closed source software is sold commercially • Usually bears label of manufacturer, such as 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 for use of certain features Linux+ Guide to Linux Certification, 3e

  19. 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 Linux+ Guide to Linux Certification, 3e

  20. 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 Linux+ Guide to Linux Certification, 3e

  21. 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 Linux+ Guide to Linux Certification, 3e

  22. Linux Advantages: Flexibility for Different Hardware Platforms • Partial list of hardware platforms on which Linux can run: • Can be customized to work on mobile and embedded devices Linux+ Guide to Linux Certification, 3e

  23. Linux Advantages:Ease of Customization • Ability to control the inner workings of the 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 • Can choose to install only software packages needed to perform required tasks • Can use shell and PERL scripts to customize or automate tasks Linux+ Guide to Linux Certification, 3e

  24. 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 Linux+ Guide to Linux Certification, 3e

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

  26. The History of Linux Figure 1-4: Timeline of UNIX and Linux development Linux+ Guide to Linux Certification, 3e

  27. 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 Linux+ Guide to Linux Certification, 3e

  28. UNIX (continued) • Berkeley Software Distribution (BSD) • Version of the original UNIX source code • Common flavors of UNIX today include: • Sun Microsystems’s Solaris UNIX • Hewlett-Packard’s HP-UX • IBM’s AIX UNIX Linux+ Guide to Linux Certification, 3e

  29. The Hacker Culture • Hacker: someone attempting to expand their computing knowledge through experimentation • Idea of sharing knowledge is fundamental to hackers • Hacker culture set the stage for the development of Linux • Cracker: someone who illegally uses computers for personal benefit or to cause damage • GNU project: free OS project started by Richard Stallman • Led to publication of GNU Public License (GPL) Linux+ Guide to Linux Certification, 3e

  30. Linux • First developed by Linus Torvalds in 1991 • Published under the GNU license • Linux kernel developed collaboratively and centrally managed • Hackers developed Linux add-on packages and distributions • Linux is simply a by-product of OSS development Linux+ Guide to Linux Certification, 3e

  31. Linux Distributions • Distribution: a collection of software containing the Linux kernel and libraries, combined with add-on software specific to a certain use. • Red Hat and SuSE • Distributions may appear different on the surface, but run the same kernel • Most distributions include a GUI that can be further customized to suit the needs of the user • Core component of this GUI is X Windows Linux+ Guide to Linux Certification, 3e

  32. Linux Distributions (continued) • GUI environment: X Windows in combination with a window manager and desktop environment – affects the look and feel of the Linux GUI • Two competing GUI environments in Linux: • GNU Object Model Environment (GNOME) • K Desktop Environment (KDE) • Some Linux distributions include specific language support Linux+ Guide to Linux Certification, 3e

  33. Linux Distributions (continued) Figure 1-5: The GNOME Desktop Linux+ Guide to Linux Certification, 3e

  34. Linux Distributions (continued) • Package manager: software system that installs and maintains software • Red Hat package manager standard on many Linux distributions • Tarball: compressed archive of files containing scripts that install software to the correct location on the system • Difficult to manage, upgrade or remove from system Linux+ Guide to Linux Certification, 3e

  35. Linux Distributions (continued) Table 1-4:Common Linux distributions Linux+ Guide to Linux Certification, 3e

  36. Linux Distributions (continued) Table 1-4 (continued): Common Linux distributions Linux+ Guide to Linux Certification, 3e

  37. 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 Linux+ Guide to Linux Certification, 3e

  38. Internet Servers: Mail Services • Mail transfer agent (MTA): an e-mail server used to distribute email • 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 Linux+ Guide to Linux Certification, 3e

  39. 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 Linux+ Guide to Linux Certification, 3e

  40. 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 • Common proxy server used on Linux is Squid Linux+ Guide to Linux Certification, 3e

  41. Internet Servers:Web Services and News Services • Web services: Web servers host information • Can process programs known as Common Gateway Interface (CGI) scripts that enable connection to a resource on the network which is not connected to the Internet • Can use Single Socket Layer (SSL) to 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 Linux+ Guide to Linux Certification, 3e

  42. 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 • DNS server: maintains a list of proper FQDN to IP mappings Linux+ Guide to Linux Certification, 3e

  43. 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 • Can share resources with a computer running another OS Linux+ Guide to Linux Certification, 3e

  44. 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 to allow for creation, modification, manipulation, maintenance, and access of information from databases • Application servers can provide management functionality Linux+ Guide to Linux Certification, 3e

  45. Supercomputers • Clustering: combining several smaller computers to act as one large supercomputer • Beowulf clustering: most common Linux method of clustering • Scalability: the ability for a computer to increase workload as the number of processors increases • Clustering computers often results in better scalability than adding processors to a single computer Linux+ Guide to Linux Certification, 3e

  46. Scientific/Engineering Workstation • Scientific and engineering community often needs customized programs • OSS programs can be used or modified • OSS software available for physics, astrophysics, biophysics, biocomputation, data mining, and many other scientific and engineering fields Linux+ Guide to Linux Certification, 3e

  47. Office/Personal Workstation • Workstation software designed for end users in office and home environments • OSS packages available for: • Graphics editing software • Desktop publishing software • Media software • Financial software • Office productivity suites • Bittorrent clients Linux+ Guide to Linux Certification, 3e

  48. 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 • Called Open Source Software (OSS) • Companies find Linux a stable, low-risk, and flexible alternative to other OSs Linux+ Guide to Linux Certification, 3e

  49. 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 Linux+ Guide to Linux Certification, 3e

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