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Transcript
Chapter 1
Introducing Linux
Guide to Linux Installation and Administration, 2e
1
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
Guide to Linux Installation and Administration, 2e
2
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
Guide to Linux Installation and Administration, 2e
3
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
Guide to Linux Installation and Administration, 2e
4
Relationship between the User,
Applications, Operating System, and
Hardware
Guide to Linux Installation and Administration, 2e
5
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
Guide to Linux Installation and Administration, 2e
6
Operating System Functions
• The major components of an operating system
include:
–
–
–
–
–
Kernel
Device drivers
Shell
Utility programs
Graphical User Interface
Guide to Linux Installation and Administration, 2e
7
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
Guide to Linux Installation and Administration, 2e
8
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
Guide to Linux Installation and Administration, 2e
9
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
Guide to Linux Installation and Administration, 2e
10
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
Guide to Linux Installation and Administration, 2e
11
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
Guide to Linux Installation and Administration, 2e
12
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
Guide to Linux Installation and Administration, 2e
13
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
Guide to Linux Installation and Administration, 2e
14
Linux Distribution
Guide to Linux Installation and Administration, 2e
15
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
Guide to Linux Installation and Administration, 2e
16
Popular Linux Distributions
Guide to Linux Installation and Administration, 2e
17
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
Guide to Linux Installation and Administration, 2e
18
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
Guide to Linux Installation and Administration, 2e
19
Standardized Versions of Linux
• The participants of the UnitedLinux
project are:
– The SCO Group (formerly Caldera
International)
– SuSE Linux
– TurboLinux
– Conectiva
Guide to Linux Installation and Administration, 2e
20
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
Guide to Linux Installation and Administration, 2e
21
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
Guide to Linux Installation and Administration, 2e
22
Careers in Linux
• Careers in Linux include:
–
–
–
–
–
–
–
System administrator
Network administrator
Software engineer
Trainer
Writer
Business consultant
Industry analyst
Guide to Linux Installation and Administration, 2e
23
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)
Guide to Linux Installation and Administration, 2e
24
The Strengths of Linux
• Linux offers key features:
– Stability
– Speed
– Security
– Low cost
Guide to Linux Installation and Administration, 2e
25
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
Guide to Linux Installation and Administration, 2e
26
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
Guide to Linux Installation and Administration, 2e
27
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
Guide to Linux Installation and Administration, 2e
28
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
Guide to Linux Installation and Administration, 2e
29
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
Guide to Linux Installation and Administration, 2e
30
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
Guide to Linux Installation and Administration, 2e
31
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
Guide to Linux Installation and Administration, 2e
32
A Multitasking, Multiuser,
Multiprocessing System
Guide to Linux Installation and Administration, 2e
33
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
Guide to Linux Installation and Administration, 2e
34
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
Guide to Linux Installation and Administration, 2e
35
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
Guide to Linux Installation and Administration, 2e
36
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
Guide to Linux Installation and Administration, 2e
37
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
Guide to Linux Installation and Administration, 2e
38
Sample Documentation Site
Guide to Linux Installation and Administration, 2e
39
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
Guide to Linux Installation and Administration, 2e
40
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
Guide to Linux Installation and Administration, 2e
41
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
Guide to Linux Installation and Administration, 2e
42
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
Guide to Linux Installation and Administration, 2e
43
Linux-Related Web Sites
Guide to Linux Installation and Administration, 2e
44
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
Guide to Linux Installation and Administration, 2e
45
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
Guide to Linux Installation and Administration, 2e
46