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  1. Chapter One 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 today

  3. Operating Systems • Every computer has two fundamental types of 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 • Once a program is executed on your computer’s hardware, that program is referred to as a process

  4. Operating Systems • Hardware components include: • Processor (CPU) • Physical memory (RAM) • Hard disk, floppy disk, and CD-ROM drives • Sound and video cards • Circuit boards

  5. Operating Systems • There are two different types or programs executed on a computer: • Applications • Operating system (OS) software Figure 1-1: The role of operating system software

  6. Operating System • Device driver • Software containing instructions the kernel of the OS uses to control and interact with a specific type of computer hardware • User interface • What the user sees and uses to interact with OS and application programs • Graphical user interface (GUI) • Component of an operating system that provides a user-friendly interface comprising graphics or icons to represent desired tasks

  7. Operating System Figure 1-2: A Linux graphical user interface • System services • Applications that handle system-related tasks such as printing, scheduling programs, and network access

  8. The Linux Operating System • Linux • Operating system used today to run a variety of applications on a variety of different hardware • Has the ability to manage thousands of tasks at the same time, including allowing multiple users to access the system simultaneously • Hence we refer to Linux as a multiuser and multitasking OS

  9. Versions of the Linux Operating System • The core component of the Linux OS is called the Linux kernel • The Linux kernel and supporting function libraries are written almost entirely in the C programming language • Though a variety of different software can be used to modify the appearance of Linux, the underlying kernel is common to all Linux

  10. Identifying Kernel Versions • Linux kernel versions are comprised of: • Major number • Minor number • If odd, referred to as a developmental kernel • If even, referred to as a production kernel • Revision number

  11. Identifying Kernel Versions Table 1-1: Latest revisions of common Linux kernels

  12. Licensing Linux • Open Source Software (OSS) • Programs distributed and licensed so that the source code making up the program is freely available to anyone who wants to examine, utilize or improve upon it • The format and structure of source code follows certain rules defined by the programming language

  13. Licensing Linux • Some implications of OSS are: • Software is developed very rapidly through widespread collaboration • Software bugs are promptly noted and fixed • Software features evolve very quickly based on users’ needs • The perceived value of the software increases, as it is based on usefulness and not price

  14. Licensing Linux Table 1-2: Software types

  15. Types of Open Source Licenses • GNU Public License (GPL) • Ensures that source code for any OSS will remain freely available to anyone • Free Software Foundation (FSF) • Promotes and encourages the collaboration of software developers worldwide • Artistic license • Open Source license that allows source code to be distributed freely, but changed only at discretion of original author

  16. Types of Closed Source Licenses • Freeware • Distributed free of charge • Source code is not available • Shareware • Initially free but require payment after a period of time or usage

  17. Linux Advantages: Risk Reduction • Companies invest in software to perform many mission-critical tasks • Changes in the market and customer needs may cause companies to change software frequently • This can be very costly and time consuming • An OSS product offers a company the opportunity to maintain and change the source code

  18. 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

  19. Linux Advantages:Stability and Security • Customers using closed source operating systems must rely on the operating system vendor to fix any bugs • Waiting for a hot fix may take weeks or months • Bugs in OSS programs can be identified and fixed very quickly • As Linux source code is freely available and scrutinized, security loopholes are also quickly identified and fixed

  20. Linux Advantages: Flexibility for Different Hardware Platforms • Partial list of hardware platforms on which Linux can run: • Intel • Itanium • Mainframe (S/390) • Cirrus Logic ARM • DEC Alpha • MIPS

  21. Linux Advantages: Flexibility for Different Hardware Platforms • Partial list of hardware platforms on which Linux can run (cont.): • M68K • PA-RISC • SPARC • Ultra-SPARC • PowerPC (Macintosh)

  22. Linux Advantages:Ease of Customization • The ability to control the inner workings of an operating system is another attractive feature of Linux • For example, if you desire to use Linux as an Internet Web server, simply compile the Linux kernel to include only the support needed to be an Internet Web server • This will result in a much smaller and faster kernel

  23. Linux Advantages: Ease of Obtaining Support • The Internet offers a world of Linux documentation • Frequently Asked Questions (FAQs) • HOWTO documents • Linux User Group (LUG) • Open forum of Linux users who discuss and assist each other in using and modifying the Linux OS

  24. Linux Advantages: Cost Reduction Table 1-3: Calculating the Total Cost of Ownership (TCO)

  25. The History of Linux Figure 1-4: Timeline of UNIX and Linux development

  26. UNIX • Multiplexed Information and Computing Service (MULTICS) • Prototype time-sharing OS developed in the late 1960s • UNIX • The first true multitasking, multiuser OS • OS from which Linux originated

  27. UNIX • BSD (Berkeley Software Distribution) • Version of the original UNIX source code • Given away free by AT&T to the University of California at Berkeley • Common flavors of UNIX today include: • Sun Microsystems’s Solaris • Hewlett-Packard’s HP-UX • IBM’s AIX UNIX

  28. The Hacker Culture • Hacker • Refers to someone with the intent of expanding their knowledge of computing through experimentation • Cracker • Specifies someone who illegally uses computers for personal benefit or to cause damage • GNU Project • Free operating system project started by Richard Stallman

  29. Linux • Finnish student Linus Torvalds first developed Linux in 1991 when he was experimenting with improving MINIX for the Intel x86 platform • During the early and mid 1990s, Linux development was radical • Also during this time, several distributions of Linux appeared, including: • Red Hat • Caldera • SuSE

  30. Linux Distributions • Linux distribution that ship with many specialized tools may not contain a GUI • An example of this would be a Linux distribution that fits on a floppy and can be used as a router • Most distribution do ship with a GUI that can be further customized to suit needs of the user • The core component of the GUI in Linux is referred to as X Windows

  31. Linux Distributions • X Windows in combination with a window manager and desktop environment is referred to as a GUI environment • There are two competing GUI environments in Linux: • GNU Object Model Environment (GNOME) • Kommon Desktop Environment (KDE)

  32. Linux Distributions Figure 1-5: The GNOME Desktop

  33. Linux Distributions Figure 1-6: The KDE Desktop

  34. Linux Distributions • Package manager • Software used to install, maintain, and remove other software programs by storing all relevant information in a central software database on the computer • Tarball • Compressed archive of files that contain scripts that install Linux software to the correct locations on the computer system

  35. Linux Distributions Table 1-4: Common Linux distributions

  36. Linux Distributions Table 1-4 (continued): Common Linux distributions

  37. Linux Distributions Table 1-4 (continued): Common Linux distributions

  38. Common Uses of Linux • Linux services may be used on the local computer workstation or they may be configured to allow other computers to connect to it across a network • Services used on a local computer are referred to as workstation services • Services made available for other computers across a network are known as server services

  39. Internet Servers: Mail Services • Mail transfer agents (MTAs) • 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

  40. Internet Servers:Routing and FTP Services • Routing • Core service that is 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

  41. Internet Servers:Firewalls and Proxy Services • Firewalls protect companies from outside intruders on the Internet • Linux has firewall support directly built into the kernel • A proxy service requests Internet resources such as Web sites and FTP sites on behalf of the computer inside the company

  42. Internet Servers:Web Services and New Services • Web services • Many Internet tools and services are available, the most popular is the Internet browser • New services • Web servers host valuable information but most do not provide any means for users to communicate with each other • This functionality is provided by a news server, which allows users to post messages in forums called newsgroups

  43. Internet Servers: DNS Services • Computers communicating on a network need to be uniquely identified • This is accomplished by assigning each computer a number called an Internet Protocol (IP) address • An IP addresses is a long string of numbers • IP addresses are masked by strings of user-friendly names, referred to as a Fully Qualified Domain Name (FQDN)

  44. File and Print Servers • Networks were created to share resources, primarily printers and information • Linux is well-suited to the task of centrally sharing resources • It is inherently a fast, light operating system, and a distribution specific to a certain task can be installed on the central server

  45. Application Servers • Application server • Server running a program that acts as an intermediary between a client computer and information, normally stored in a database • Database Management Systems (DBMS) • Collection of programs and tools designed to allow for the creation, modification, manipulation, maintenance, and access of information from databases

  46. Supercomputers • Cluster • Several smaller computers acting as one large supercomputer • Clustering • Act of making a cluster • Most common Linux method of clustering is known as Beowulf clustering • Scalability • Ability of computers to increase workload as the number of processors increases

  47. Scientific/Engineering Workstations • There are many OSS programs available in many different scientific and engineering fields, including: • Physics, astrophysics, and biophysics • Fluid dynamics and geophysics • Biocomputation • Materials and polymer chemistry • General mathematics and optimization • Data mining • Number theory

  48. Scientific/Engineering Workstations • There are many OSS programs available in many different scientific and engineering fields, including (cont.): • Computer/linear/array algebra • Mathematical visualization and modeling • Statistics and regression analysis • Data plotting and processing • Computer graphics generation • Computer modeling

  49. Scientific/Engineering Workstations • There are many OSS programs available in many different scientific and engineering fields, including (cont.): • Paleontology • Molecular modeling • Electrical engineering • Artificial intelligence • Geographic modeling and earth sciences • Oceanography

  50. Office Workstations:Text Editors and Word Processors • Text editor • Program that can create and edit text files • Word processors • Allow the creation and manipulation of text files • Typically GUI-based