Guide to Linux Installation and Administration, 2e1 Chapter 1 Introducing Linux

Guide to Linux Installation and Administration, 2e 1

Chapter 1

Introducing Linux


Objectives

In this chapter, you will:

• Explain how an operating system works

• Explain how and why Linux was created

• Describe career options related to Linux

• Describe some benefits of using Linux

• Locate additional information about Linux commands and features


Understanding Operating Systems

• Operating system

– provides an interface between computer hardware and user applications

– manages memory, CPU time, and other system resources

• A complete operating system includes many other features to provide additional hardware support, a graphical environment, and utility programs

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Defining an Operating System

• Software: collection of instructions that control the tasks that a computer performs

• A set of core functionality that many programs can use to control a computer is called an operating system

• Application: software program that provides a service to the person using the computer, rather than simply controlling the computer’s hardware


Relationship between the User, Applications, Operating System, and

Hardware


Operating System Functions

• An operating system provides basic services to every application running on the computer:– Initialize (or prepare) the computer hardware

– Allocate system resources to the programs that are using the operating system

– Keep track of multiple programs running at the same time

– Provide an organized method for all programs to use system devices


Operating System Functions

• The major components of an operating system include:– Kernel

– Device drivers

– Shell

– Utility programs

– Graphical User Interface


Commonly Used Operating Systems

• The UNIX operating system was created at AT&T Bell Labs in the early 1970s by Ken Thompson and Dennis Ritchie

• The first version of the Disk Operating System (DOS) for IBM personal computers was created in about 1980 by Microsoft

• In 1984 Apple Computer introduced the Macintosh, which integrated the operating system and the graphical interface

• In August 1995 Microsoft introduced the Windows 95 operating system, which integrated a copy of DOS and a copy of Windows


Linux Arrives

• In 1991 Linus Torvalds decided to create a UNIX-like operating system kernel for his IBM-compatible PC as a school project

• Torvalds solicited help via the Internet• Hundreds of programmers around the world were

working together to create a new Linux kernel


The Linux Software License

• A software license is a legal definition of who can use a piece of software and how it can be used

• Torvalds decided to base the software license for the Linux kernel on a model created by Richard Stallman and the Free Software Foundation


The Free Software Foundation and the GNU Project

• In 1983 Richard Stallman at the Massachusetts Institute of Technology founded an organization called the Free Software Foundation (FSF)

• With the GNU project, Stallman intended to create a completely free version of UNIX, written from scratch

• Hundreds of software programs as part of the GNU project are included with the Linux kernel in each copy of a complete Linux operating system


The GNU General Public License (GPL)

• The General Public License (GPL) requires that source code be distributed with each copy of the Linux kernel– The source code is the set of human-readable

programming instructions used to create the program

• Anyone who obtains a copy of the software can redistribute it in any form

• Anyone can modify the software, the modifications are automatically subject to the GPL


How Linux Is Developed• Linux kernel development follows the model of

most free software projects• A person identifies a need and begins writing a

program• The software developer announces the project on

the Internet• Developers who share an interest in that project

respond, and soon they begin to work together on different parts of the project

• The project lead releases the software (including source code) on the Internet to try it and fix the bugs


Linux Distributions

• Various companies have created commercial products, called distributions, that are built around the Linux kernel and GNU software

• Linux distribution includes many software components, installation tools, documentation, and system utilities


Linux Distribution


Distributions in the Marketplace

• Many companies have created Linux distributions• These companies include in their distributions

the source code for the Linux kernel and utilities• Companies add to a typical distribution

installation tools, professional documentation, technical support, and specialized software

• They can charge as much as they choose for their Linux distributions


Popular Linux Distributions


The Future of Linux Development

• Linux companies like Red Hat Software make Linux a viable commercial option for large organizations

• Linux companies also contribute money and personnel toward developing and refining the free software on which their business is built

• Linux vendors create more integrated, easier-to-use products

• Linux does have increasingly broad support in the business world


Standardized Versions of Linux

• Efforts to standardize Linux distributions could make it easier for software developers to write applications for the larger Linux market

• The first major effort in this direction was called Linux Standard Base (LSB)

• The UnitedLinux project is the second effort aimed at creating a foundation Linux distribution for multiple Linux vendors


Standardized Versions of Linux

• The participants of the UnitedLinux project are:– The SCO Group (formerly Caldera

International)

– SuSE Linux

– TurboLinux

– Conectiva


Version Numbering

• Each release of the Linux kernel is assigned a version number

• The kernel version includes three parts:– A major version number

– A minor version number

– A patch level number

• A version number for the stable release might look like this: 2.4.18


Motivating Free Software Developers

• Linux developers have their own motivations:– Developer’s specific technical needs

– The respect of likeminded professionals

– A sense of contribution and community to developer’s

– A valuable boost to any developer’s resume

– Proven technical ability and strength at working in a team and organizing the work of others


Careers in Linux

• Careers in Linux include:– System administrator

– Network administrator

– Software engineer

– Trainer

– Writer

– Business consultant

– Industry analyst


Linux Certification

• Obtaining a Linux certification demonstrates to potential employers that you have mastered basic Linux skills.

• Several Linux certification programs are currently available:– SAIR/GNU (the LCA program)

– Linux Professional Institute (the LPI program)

– CompTIA (the Linux+ program);

– Red Hat Software (the Red Hat Certified Engineer program)


The Strengths of Linux

• Linux offers key features:– Stability– Speed– Security– Low cost


Stability

• Linux has a strong reputation for stability• This stability is due to both the quality and the

design of Linux• Programming errors are discovered during the

development stage and are fixed before the stable system is released

• There is no market-driven deadlines or fixed release schedules


Security

• Security problems almost always relate to programs running on Linux

• All interested developers can help identify and fix security problems

• When users do discover security problems, Linux developers will create a software update to fix the problem within about 24 hours


Speed

• Linux was designed to use limited hardware resources efficiently

• The efficiency of Linux when operating with such limited resources translates into speed when more extensive resources are available


Cost

• Price is usually not the deciding factor for an organization that selects Linux

• Linux offers features like stability, speed, and security that are similar to other operating systems costing thousands of dollars

• Linux price is the range between $2 and $100


A Multitasking System

• Linux manages multiple programs through a technology called preemptive multitasking

• The Linux kernel maintains overall control of each program and of the system resources used by each program

• Other operating systems use cooperative multitasking in which the kernel is forced to wait for a program to yield control


A Multiuser System

• Multiple users can log in to the same Linux system over a network connection and run programs

• A superuser, or administrative account, can configure and control all user accounts

• Users must log in to a Linux system using a valid username and password before doing any work


A Multiprocessing System

• Linux also supports multiple CPUs on the same computer using a technology called symmetrical multiprocessing

• A software developer divides the components of a task into threads, or subtasks

• Linux can then assign each thread of an application to a separate processor via a technique called multithreading


A Multitasking, Multiuser, Multiprocessing System


Flexibility

• Linux distributions are extremely flexible because they always include the source code to the operating system

• Technically oriented system administrators and software developers can modify a system any way they choose

• Commercial Linux vendors such as SuSE and Red Hat Software provide the technical support


Applications

• StarOffice, a complete graphical office suite similar to Microsoft Office, from Sun Microsystems

• Adobe Acrobat document reader• Popular games from top entertainment

companies like Loki• Database products from Oracle, Sybase, IBM, and

many others


Applications

• Java technology, both within browsers and stand-alone

• Web server software and supporting development tools

• E-mail servers with graphical configuration interfaces

• Security tools such as routers and firewalls


Reading Linux Documentation

• Linux developers share descriptions of their software via electronic or online documentation

• This documentation was typically incorporated into the project when it was distributed for everyone’s use


The Linux Documentation Project

• The Linux Documentation Project (LDP) was begun by Matt Welsh in the early 1990s

• The LDP currently contains over 6000 pages of• documentation, all of which is available online,

free of charge, under a version of the GPL• The LDP consists of several types of documents,

including online reference manuals and HOWTO documents


Sample Documentation Site


The Linux Documentation Project

• The HOWTOs cover specific topics• Each document is written by one person, or a

small group, with expertise in that topic• Documents called mini-HOWTOs focus on

narrower subjects than do regular HOWTOs• HOWTO documents are intended for readers who

are not familiar with the topic being discussed


Linux Command Information

• The Linux command information is provided in two formats:– man pages

– info pages

• You can access online manual pages for most Linux commands by using the man command

• You can view info pages using the info command


Documentation Included with Software Packages

• Most of the software packages included with a Linux distribution provide the documentation

• You can view the documentation either in a text editor or a Web browser

• The documentation is stored in the /usr/doc or /usr/share/doc subdirectory of the file system


Linux on the Internet

• Many publications and Web sites maintain daily news updates about what is happening in the world of Linux and free software

• The Web sites for each of the Linux distributions are great resources for learning about Linux


Linux-Related Web Sites


Summary• An operating system provides an interface

between the computer hardware and the applications run by the user.

• The Linux kernel was created by many talented individuals from around the world working under the leadership of Linus Torvalds

• The Free Software Foundation, led by Richard Stallman, created hundreds of software programs as part of its GNU project to include them with the Linux kernel in each copy of a complete Linux operating system

• The General Public License (GPL) requires that source code be distributed with each copy of the Linux kernel


Summary

• Linux offers key features such as stability, speed, security, flexibility, and low cost

• Careers in Linux include system administrators, software developers, technical writers, industry analysts, and others

• Obtaining a Linux certification demonstrates to potential employers that you have mastered basic Linux skills

• Information about Linux is available online as part of the Linux Documentation Project, which includes HOWTO documents on specific topics