Linux+ Guide to Linux Certification Chapter One Introduction to Linux

Linux+ Guide to Linux Certification

Chapter One

Introduction to Linux

ObjectivesObjectives

• 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

Operating SystemsOperating 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

Operating SystemsOperating Systems

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

Operating SystemsOperating 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

Operating SystemOperating 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

Operating SystemOperating System

• System services– Applications

that handle system-related tasks such as printing, scheduling programs, and network access

Figure 1-2: A Linux graphical user interface

The Linux Operating SystemThe 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

Versions of the Linux Operating Versions of the Linux Operating SystemSystem

• 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

Identifying Kernel VersionsIdentifying 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

Identifying Kernel VersionsIdentifying Kernel Versions

Table 1-1: Latest revisions of common Linux kernels

Licensing LinuxLicensing 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

Licensing LinuxLicensing 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

Licensing LinuxLicensing Linux

Table 1-2: Software types

Types of Open Source LicensesTypes 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

Types of Closed Source LicensesTypes 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

Linux Advantages: Risk ReductionLinux 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

Linux Advantages:Linux Advantages:Meeting Business NeedsMeeting 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 Advantages:Linux Advantages:Stability and SecurityStability 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

Linux Advantages: Flexibility for Linux Advantages: Flexibility for Different Hardware PlatformsDifferent Hardware Platforms

• Partial list of hardware platforms on which Linux can run:– Intel

– Itanium

– Mainframe (S/390)

– Cirrus Logic ARM

– DEC Alpha

– MIPS

Linux Advantages: Flexibility for Linux Advantages: Flexibility for Different Hardware PlatformsDifferent Hardware Platforms

• Partial list of hardware platforms on which Linux can run (cont.):– M68K– PA-RISC– SPARC– Ultra-SPARC– PowerPC (Macintosh)

Linux Advantages:Linux Advantages:Ease of CustomizationEase 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

Linux Advantages: Ease of Linux Advantages: Ease of Obtaining SupportObtaining 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

Linux Advantages: Cost ReductionLinux Advantages: Cost Reduction

Table 1-3: Calculating the Total Cost of Ownership (TCO)

The History of LinuxThe History of Linux

Figure 1-4: Timeline of UNIX and Linux development

UNIXUNIX

• 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

UNIXUNIX

• 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

The Hacker CultureThe 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

LinuxLinux

• 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

Linux DistributionsLinux 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

Linux DistributionsLinux 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)

Linux DistributionsLinux Distributions

Figure 1-5: The GNOME Desktop

Linux DistributionsLinux Distributions

Figure 1-6: The KDE Desktop

Linux DistributionsLinux 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

Linux DistributionsLinux Distributions

Table 1-4: Common Linux distributions

Linux DistributionsLinux Distributions

Table 1-4 (continued): Common Linux distributions

Linux DistributionsLinux Distributions

Table 1-4 (continued): Common Linux distributions

Common Uses of LinuxCommon 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

Internet Servers: Mail ServicesInternet 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

Internet Servers:Internet Servers:Routing and FTP ServicesRouting 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

Internet Servers:Internet Servers:Firewalls and Proxy ServicesFirewalls 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

Internet Servers:Internet Servers:Web Services and New ServicesWeb 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

Internet Servers: DNS ServicesInternet 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)

File and Print ServersFile 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

Application ServersApplication 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

SupercomputersSupercomputers

• 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

Scientific/Engineering Scientific/Engineering WorkstationsWorkstations

• 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

Scientific/Engineering Scientific/Engineering WorkstationsWorkstations

• 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

Scientific/Engineering Scientific/Engineering WorkstationsWorkstations

• 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

Office Workstations:Office Workstations:Text Editors and Word ProcessorsText 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

Office Workstations: Graphics Editing Office Workstations: Graphics Editing and Desktop Publishing Softwareand Desktop Publishing Software

• Graphics editing software– Includes applications designed to create and

manipulate graphical images

• Desktop publishing software– Combines text and graphics editing software

together and adds features that allow one to control format and layout

Office Workstations: Financial Software Office Workstations: Financial Software and Office Productivity Suitesand Office Productivity Suites

• Financial software– Describes a family of applications designed to:

• Track financial transactions

• Perform bookkeeping and accounting procedures

• Office productivity suites– Collection of applications offered in combination

to meet a variety of needs seen in business or the home

Chapter SummaryChapter Summary

• Linux is an operating system (OS) whose kernel and many additional software packages are freely developed and improved upon by a large community of software developers in collaboration

• Since Linux is published under GNU Public License, it is referred to as Open source Software

• Companies find Linux a stable, low-risk, and flexible alternative to other operating systems

Chapter SummaryChapter Summary

• Linux is available in different distributions• There exists a wide variety of documentations

and resources for Linux in the form of Internet Web sites, HOWTOs, FAQs, newsgroups, and LUGs

• Linux is an extremely versatile OS that can provide a wide range of workstations and server services to meet computing needs of companies and individuals