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Chapter 1
Introducing Linux
Guide to Linux Installation and Administration, 2e
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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
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Valued Gateway
Client:
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
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Relationship between the User,
Applications, Operating System, and
Hardware
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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
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Operating System Functions
• The major components of an operating system
include:
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–
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–
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Kernel
Device drivers
Shell
Utility programs
Graphical User Interface
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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
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Linux Arrives
• In 1991 Linus Torvalds decided to create a UNIXlike operating system kernel for his IBMcompatible 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
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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
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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
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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
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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
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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
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Linux Distribution
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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
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Popular Linux Distributions
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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-touse products
• Linux does have increasingly broad support in
the business world
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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
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Standardized Versions of Linux
• The participants of the UnitedLinux
project are:
– The SCO Group (formerly Caldera
International)
– SuSE Linux
– TurboLinux
– Conectiva
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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
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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
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Careers in Linux
• Careers in Linux include:
–
–
–
–
–
–
–
System administrator
Network administrator
Software engineer
Trainer
Writer
Business consultant
Industry analyst
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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)
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The Strengths of Linux
• Linux offers key features:
– Stability
– Speed
– Security
– Low cost
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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
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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
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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
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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
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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
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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
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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
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A Multitasking, Multiuser,
Multiprocessing System
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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
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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
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Applications
• Java technology, both within browsers and standalone
• Web server software and supporting development
tools
• E-mail servers with graphical configuration
interfaces
• Security tools such as routers and firewalls
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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
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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
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Sample Documentation Site
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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
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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
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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
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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
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Linux-Related Web Sites
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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
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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
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