PC Online 1996 November/PCO96_11.ISO/linux/docs/install/install.txt

Text File | 1996-09-21 | 97.0 KB | 1,735 lines

Author's Note:

This is version 2.2.2 of the book, "Linux Installation and Getting
Started", formatted in plain ASCII for those readers without access
to PostScript printers. This document was generated by a set of tools
from LaTeX source, so there may be a number of formatting problems.
This is not the "official" version of the book! Please see
    sunsite.unc.edu:/pub/Linux/docs/LDP/install-guide
for PostScript, DVI, HTML, and other (nicely formatted) versions.
If you have the ability to print the guide or view it on-line,
I suggest you do so. This ASCII version is meant only for previewing
purposes.

This book may be freely distributed under certain conditions, and
you can order a printed and bound copy from a number of publishers.
The README file at the FTP site given above gives all the details.

                    -- M. Welsh













Linux Installation and Getting Started
_______________________________________________________________________
                                  Copyright (c) 1992--1994  Matt Welsh






Version 2.2.2, 11 February 1995.

This  book   is   an  installation   and   new-user  guide   for   the
Linux system,  meant for  UNIX novices  and  gurus alike.    Contained
herein is  information on  how to  obtain Linux,  installation of  the
software, a beginning tutorial for new UNIX users, and an introduction
to system administration.    It is meant  to be  general enough to  be
applicable to any distribution of the Linux software.

  This book is freely distributable; you may copy  and redistribute it
under certain conditions.   Please see the copyright and  distribution
statement on page x.









Contents




Preface                                                             vi
  Audience  . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
  Organization  . . . . . . . . . . . . . . . . . . . . . . . . . . vii
  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . vii
  Credits and Legalese  . . . . . . . . . . . . . . . . . . . . . . viii
  Documentation Conventions . . . . . . . . . . . . . . . . . . . . xi
1 Introduction to Linux                                              1
  1.1 About This Book . . . . . . . . . . . . . . . . . . . . . . .  1
  1.2 A Brief History of Linux  . . . . . . . . . . . . . . . . . .  3
  1.3 System Features . . . . . . . . . . . . . . . . . . . . . . .  5
  1.4 Software Features . . . . . . . . . . . . . . . . . . . . . .  6
    1.4.1 Basic commands and utilities  . . . . . . . . . . . . . .  7
    1.4.2 Text processing and word processing . . . . . . . . . . .  8
    1.4.3 Programming languages and utilities . . . . . . . . . . . 11
    1.4.4 The X Window System . . . . . . . . . . . . . . . . . . . 12
    1.4.5 Networking  . . . . . . . . . . . . . . . . . . . . . . . 14
    1.4.6 Telecommunications and BBS software . . . . . . . . . . . 15
    1.4.7 Interfacing with MS-DOS . . . . . . . . . . . . . . . . . 16
    1.4.8 Other applications  . . . . . . . . . . . . . . . . . . . 16
  1.5 About Linux's Copyright . . . . . . . . . . . . . . . . . . . 18
  1.6 The Design and Philosophy of Linux  . . . . . . . . . . . . . 19
    1.6.1 Hints for UNIX novices  . . . . . . . . . . . . . . . . . 22
    1.6.2 Hints for UNIX gurus  . . . . . . . . . . . . . . . . . . 22
  1.7 Differences Between Linux and Other Operating Systems . . . . 23
    1.7.1 Why use Linux?  . . . . . . . . . . . . . . . . . . . . . 23
    1.7.2 Linux vs.  MS-DOS . . . . . . . . . . . . . . . . . . . . 24
    1.7.3 Linux vs.  The Other Guys . . . . . . . . . . . . . . . . 25
    1.7.4 Other implementations of UNIX . . . . . . . . . . . . . . 25
  1.8 Hardware Requirements . . . . . . . . . . . . . . . . . . . . 27
    1.8.1 Motherboard and CPU requirements  . . . . . . . . . . . . 28
    1.8.2 Memory requirements . . . . . . . . . . . . . . . . . . . 28
    1.8.3 Hard drive controller requirements  . . . . . . . . . . . 29
    1.8.4 Hard drive space requirements . . . . . . . . . . . . . . 29
    1.8.5 Monitor and video adapator requirements . . . . . . . . . 30
    1.8.6 Miscellaneous hardware  . . . . . . . . . . . . . . . . . 30
    1.8.7 Ethernet cards  . . . . . . . . . . . . . . . . . . . . . 31
  1.9 Sources of Linux Information  . . . . . . . . . . . . . . . . 32
    1.9.1 Online documents  . . . . . . . . . . . . . . . . . . . . 32


                                  i


    1.9.2 Linux on the World Wide Web . . . . . . . . . . . . . . . 33
    1.9.3 Books and other published works . . . . . . . . . . . . . 33
    1.9.4 USENET newsgroups . . . . . . . . . . . . . . . . . . . . 34
    1.9.5 Internet mailing lists  . . . . . . . . . . . . . . . . . 36
  1.10 Getting Help . . . . . . . . . . . . . . . . . . . . . . . . 37

2 Obtaining and Installing Linux                                    40
  2.1 Distributions of Linux  . . . . . . . . . . . . . . . . . . . 40
    2.1.1 Getting Linux from the Internet . . . . . . . . . . . . . 41
    2.1.2 Getting Linux from other online sources . . . . . . . . . 42
    2.1.3 Getting Linux via mail order  . . . . . . . . . . . . . . 42
    2.1.4 Getting Slackware . . . . . . . . . . . . . . . . . . . . 43
  2.2 Preparing to Install Linux  . . . . . . . . . . . . . . . . . 50
    2.2.1 Installation overview . . . . . . . . . . . . . . . . . . 50
    2.2.2 Repartitioning concepts . . . . . . . . . . . . . . . . . 52
    2.2.3 Linux partition requirements  . . . . . . . . . . . . . . 52
    2.2.4 Repartitioning your drives  . . . . . . . . . . . . . . . 54
  2.3 Installing the Linux software . . . . . . . . . . . . . . . . 56
    2.3.1 Booting Linux . . . . . . . . . . . . . . . . . . . . . . 56
    2.3.2 Drives and partitions under Linux . . . . . . . . . . . . 58
    2.3.3 Creating Linux partitions . . . . . . . . . . . . . . . . 60
    2.3.4 Creating the swap space . . . . . . . . . . . . . . . . . 63
    2.3.5 Creating the filesystems  . . . . . . . . . . . . . . . . 64
    2.3.6 Installing the software . . . . . . . . . . . . . . . . . 65
    2.3.7 Creating the boot floppy or installing LILO . . . . . . . 69
    2.3.8 Additional installation procedures  . . . . . . . . . . . 70
  2.4 Postinstallation procedures . . . . . . . . . . . . . . . . . 70
  2.5 Running Into Trouble  . . . . . . . . . . . . . . . . . . . . 71
    2.5.1 Problems with booting the installation media  . . . . . . 72
    2.5.2 Hardware problems . . . . . . . . . . . . . . . . . . . . 74
    2.5.3 Problems installing the software  . . . . . . . . . . . . 79
    2.5.4 Problems after installing Linux . . . . . . . . . . . . . 81
3 Linux Tutorial                                                    85
  3.1 Introduction  . . . . . . . . . . . . . . . . . . . . . . . . 85
  3.2 Basic UNIX Concepts . . . . . . . . . . . . . . . . . . . . . 86
    3.2.1 Creating an account . . . . . . . . . . . . . . . . . . . 86
    3.2.2 Logging in  . . . . . . . . . . . . . . . . . . . . . . . 86
    3.2.3 Virtual consoles  . . . . . . . . . . . . . . . . . . . . 87
    3.2.4 Shells and commands . . . . . . . . . . . . . . . . . . . 87
    3.2.5 Logging out . . . . . . . . . . . . . . . . . . . . . . . 89
    3.2.6 Changing your password  . . . . . . . . . . . . . . . . . 89
    3.2.7 Files and directories . . . . . . . . . . . . . . . . . . 89
    3.2.8 The directory tree  . . . . . . . . . . . . . . . . . . . 90
    3.2.9 The current working directory . . . . . . . . . . . . . . 90
    3.2.1 0Referring to home directories  . . . . . . . . . . . . . 92
  3.3 First Steps into UNIX . . . . . . . . . . . . . . . . . . . . 92
    3.3.1 Moving around . . . . . . . . . . . . . . . . . . . . . . 92
    3.3.2 Looking at the contents of directories  . . . . . . . . . 93
    3.3.3 Creating new directories  . . . . . . . . . . . . . . . . 95
    3.3.4 Copying files . . . . . . . . . . . . . . . . . . . . . . 96


    3.3.5 Moving files  . . . . . . . . . . . . . . . . . . . . . . 96
    3.3.6 Deleting files and directories  . . . . . . . . . . . . . 96
    3.3.7 Looking at files  . . . . . . . . . . . . . . . . . . . . 97
    3.3.8 Getting online help . . . . . . . . . . . . . . . . . . . 97
  3.4 Summary of Basic Commands . . . . . . . . . . . . . . . . . . 98
  3.5 Exploring the File System  . . . . . . . . . . . . . . . . . 100
  3.6 Types of shells  . . . . . . . . . . . . . . . . . . . . . . 105
  3.7 Wildcards  . . . . . . . . . . . . . . . . . . . . . . . . . 106
  3.8 UNIX Plumbing  . . . . . . . . . . . . . . . . . . . . . . . 108
    3.8.1 Standard input and output  . . . . . . . . . . . . . . . 108
    3.8.2 Redirecting input and output . . . . . . . . . . . . . . 109
    3.8.3 Using pipes  . . . . . . . . . . . . . . . . . . . . . . 110
    3.8.4 Non-destructive redirection  . . . . . . . . . . . . . . 112
  3.9 File Permissions . . . . . . . . . . . . . . . . . . . . . . 112
    3.9.1 Concepts of file permissions . . . . . . . . . . . . . . 112
    3.9.2 Interpreting file permissions  . . . . . . . . . . . . . 113
    3.9.3 Dependencies . . . . . . . . . . . . . . . . . . . . . . 114
    3.9.4 Changing permissions . . . . . . . . . . . . . . . . . . 115
  3.10 Managing file links . . . . . . . . . . . . . . . . . . . . 115
    3.10.1 Hard links  . . . . . . . . . . . . . . . . . . . . . . 115
    3.10.2 Symbolic links  . . . . . . . . . . . . . . . . . . . . 117
  3.11 Job Control . . . . . . . . . . . . . . . . . . . . . . . . 117
    3.11.1 Jobs and processes  . . . . . . . . . . . . . . . . . . 117
    3.11.2 Foreground and background . . . . . . . . . . . . . . . 118
    3.11.3 Backgrounding and killing jobs  . . . . . . . . . . . . 119
    3.11.4 Stopping and restarting jobs  . . . . . . . . . . . . . 121
  3.12 Using the vi Editor . . . . . . . . . . . . . . . . . . . . 123
    3.12.1 Concepts  . . . . . . . . . . . . . . . . . . . . . . . 124
    3.12.2 Starting vi . . . . . . . . . . . . . . . . . . . . . . 124
    3.12.3 Inserting text  . . . . . . . . . . . . . . . . . . . . 125
    3.12.4 Deleting text . . . . . . . . . . . . . . . . . . . . . 126
    3.12.5 Changing text . . . . . . . . . . . . . . . . . . . . . 127
    3.12.6 Moving commands . . . . . . . . . . . . . . . . . . . . 128
    3.12.7 Saving files and quitting vi  . . . . . . . . . . . . . 128
    3.12.8 Editing another file  . . . . . . . . . . . . . . . . . 129
    3.12.9 Including other files . . . . . . . . . . . . . . . . . 129
    3.12.10 Running shell commands . . . . . . . . . . . . . . . . 130
    3.12.11 Getting help . . . . . . . . . . . . . . . . . . . . . 130
  3.13Customizing your Environment . . . . . . . . . . . . . . . . 130
    3.13.1 Shell scripts . . . . . . . . . . . . . . . . . . . . . 131
    3.13.2 Shell variables and the environment . . . . . . . . . . 132
    3.13.3 Shell initialization scripts  . . . . . . . . . . . . . 135
  3.14 So You Want to Strike Out on Your Own?  . . . . . . . . . . 135

4 System Administration                                            137
  4.1  About Root, Hats, and the Feeling of Power  . . . . . . . . 137
    4.1.1 The root account . . . . . . . . . . . . . . . . . . . . 137
    4.1.2 Abusing the system . . . . . . . . . . . . . . . . . . . 139
    4.1.3 Dealing with users . . . . . . . . . . . . . . . . . . . 139
    4.1.4 Setting the rules  . . . . . . . . . . . . . . . . . . . 140
    4.1.5 What it all means  . . . . . . . . . . . . . . . . . . . 140


  4.2  Booting the System  . . . . . . . . . . . . . . . . . . . . 141
    4.2.1 Using a boot floppy  . . . . . . . . . . . . . . . . . . 141
    4.2.2 Using LILO . . . . . . . . . . . . . . . . . . . . . . . 142
  4.3 Shutting Down  . . . . . . . . . . . . . . . . . . . . . . . 143
  4.4 Managing Users . . . . . . . . . . . . . . . . . . . . . . . 144
    4.4.1 User management concepts . . . . . . . . . . . . . . . . 144
    4.4.2 Adding users . . . . . . . . . . . . . . . . . . . . . . 146
    4.4.3 Deleting users . . . . . . . . . . . . . . . . . . . . . 146
    4.4.4 Setting user attributes  . . . . . . . . . . . . . . . . 146
    4.4.5 Groups . . . . . . . . . . . . . . . . . . . . . . . . . 147
  4.5 Archiving and Compressing Files  . . . . . . . . . . . . . . 147
    4.5.1 Using tar  . . . . . . . . . . . . . . . . . . . . . . . 148
    4.5.2 gzip and compress  . . . . . . . . . . . . . . . . . . . 149
    4.5.3 Putting them together  . . . . . . . . . . . . . . . . . 149
  4.6 Using Floppies and Making Backups  . . . . . . . . . . . . . 151
    4.6.1 Using floppies for backups . . . . . . . . . . . . . . . 151
    4.6.2 Using floppies as filesystems  . . . . . . . . . . . . . 151
  4.7 Upgrading and Installing New Software  . . . . . . . . . . . 152
    4.7.1 Upgrading the kernel . . . . . . . . . . . . . . . . . . 153
    4.7.2 Upgrading the libraries  . . . . . . . . . . . . . . . . 154
    4.7.3 Upgrading gcc  . . . . . . . . . . . . . . . . . . . . . 155
    4.7.4 Upgrading other software . . . . . . . . . . . . . . . . 156
  4.8 Managing Filesystems . . . . . . . . . . . . . . . . . . . . 156
    4.8.1 Mounting filesystems . . . . . . . . . . . . . . . . . . 156
    4.8.2 Checking filesystems . . . . . . . . . . . . . . . . . . 158
  4.9 Using a swap file  . . . . . . . . . . . . . . . . . . . . . 159
  4.10 Miscellaneous Tasks . . . . . . . . . . . . . . . . . . . . 160
    4.10.1 System startup files  . . . . . . . . . . . . . . . . . 160
    4.10.2 Setting the hostname  . . . . . . . . . . . . . . . . . 161
  4.11 What To Do In An Emergency  . . . . . . . . . . . . . . . . 162
    4.11.1 Recovering using a maintenance diskette . . . . . . . . 162
    4.11.2 Fixing the root password  . . . . . . . . . . . . . . . 163
    4.11.3 Fixing trashed filesystems  . . . . . . . . . . . . . . 163
    4.11.4 Recovering lost files . . . . . . . . . . . . . . . . . 164
    4.11.5 Fixing trashed libraries  . . . . . . . . . . . . . . . 164

5 Advanced Features                                                165
  5.1 The X Window System  . . . . . . . . . . . . . . . . . . . . 165
    5.1.1 Hardware requirements  . . . . . . . . . . . . . . . . . 166
    5.1.2 Installing XFree86 . . . . . . . . . . . . . . . . . . . 168
    5.1.3 Configuring XFree86  . . . . . . . . . . . . . . . . . . 170
    5.1.4 Filling in video card information  . . . . . . . . . . . 178
    5.1.5 Running XFree86  . . . . . . . . . . . . . . . . . . . . 182
    5.1.6 Running into trouble . . . . . . . . . . . . . . . . . . 183
  5.2 Accessing MS-DOS Files . . . . . . . . . . . . . . . . . . . 184
  5.3 Networking with TCP/IP . . . . . . . . . . . . . . . . . . . 185
    5.3.1 Hardware Requirements  . . . . . . . . . . . . . . . . . 186
    5.3.2 Configuring TCP/IP on your system  . . . . . . . . . . . 186
    5.3.3 SLIP Configuration . . . . . . . . . . . . . . . . . . . 194
    5.3.4 Using dip  . . . . . . . . . . . . . . . . . . . . . . . 197
  5.4 Networking with UUCP . . . . . . . . . . . . . . . . . . . . 199
                                                                     v
_______________________________________________________________________

  5.5 Electronic Mail  . . . . . . . . . . . . . . . . . . . . . . 200
  5.6 News and USENET  . . . . . . . . . . . . . . . . . . . . . . 200

A Sources of Linux Information                                     203
  A.1 Online Documents . . . . . . . . . . . . . . . . . . . . . . 203
  A.2 Linux Documentation Project Manuals  . . . . . . . . . . . . 205
  A.3 Books and Other Published Works  . . . . . . . . . . . . . . 206
    A.3.1 Using UNIX . . . . . . . . . . . . . . . . . . . . . . . 207
    A.3.2 Systems Administration . . . . . . . . . . . . . . . . . 207
    A.3.3 The X Window System  . . . . . . . . . . . . . . . . . . 208
    A.3.4 Programming  . . . . . . . . . . . . . . . . . . . . . . 208
    A.3.5 Kernel Hacking . . . . . . . . . . . . . . . . . . . . . 209
B Linux Vendor List                                                211

C FTP Tutorial and Site List                                       214
  C.1 Starting ftp . . . . . . . . . . . . . . . . . . . . . . . . 214
  C.2 Logging In . . . . . . . . . . . . . . . . . . . . . . . . . 215
  C.3 Poking Around  . . . . . . . . . . . . . . . . . . . . . . . 215
  C.4 Downloading files  . . . . . . . . . . . . . . . . . . . . . 217
  C.5 Quitting FTP   . . . . . . . . . . . . . . . . . . . . . . . 219
  C.6 Using ftpmail  . . . . . . . . . . . . . . . . . . . . . . . 220
  C.7 Linux FTP Site List  . . . . . . . . . . . . . . . . . . . . 220
D Linux BBS List                                                   222
  D.1 United States  . . . . . . . . . . . . . . . . . . . . . . . 222
  D.2 Outside of the United States . . . . . . . . . . . . . . . . 224

E The GNU General Public License                                   227
  E.1 Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . 227
  E.2 Terms  and  Conditions  for  Copying,   Distribution,  and
    Modification  . . . . . . . . . . . . . . . . . . . . . . . .  228
  E.3 Appendix:  How to Apply These Terms to Your New Programs . . 233









Preface



``You are in a maze of twisty little passages, all alike.''
  Before you looms  one of the  most complex and utterly  intimidating
systems ever written.   Linux,  the free UNIX  clone for the  personal
computer, produced by a mishmash team of UNIX gurus, hackers,  and the
occasional loon.   The system itself  reflects this complex  heritage,
and although the development of Linux may appear to be  a disorganized
volunteer effort, the system  is powerful, fast,  and free.   It is  a
true 32-bit operating system solution.
  My  own experiences  with  Linux began  several  years ago,  when  I
sat down  to  figure out  how  to  install the  only  ``distribution''
available at the time---a couple  of diskettes made available by  H.J.
Lu.   I  downloaded a  slew  of files  and read  pages  upon pages  of
loosely-organized installation notes.   Somehow, I managed to  install
this basic  system and  get everything  working together.    This  was
long before you could buy the Linux software on CD-ROM  from worldwide
distributors; before, in fact, Linux even knew how to  access a CD-ROM
drive.   This  was before  XFree86,  before Emacs,  before  commercial
software support,  and before  Linux became  a true  rival to  MS-DOS,
Microsoft Windows, and OS/2 in the personal computer market.
  You hold in  your very hands the map  and guidebook to the  world of
Linux.  It is my hope that this book will help you to get rolling with
what I consider to be the fastest, most powerful  operating system for
the personal computer.    Setting up your  own Linux  system can be  a
great deal of fun---so grab a cup of coffee, sit back, and read on.
  Grab a cup for  me, too, while you're at  it.  I've been  up hacking
Linux for days.


Audience

This book is for any personal  computer user who wants to  install and
use Linux on their system.   We assume  that you have basic  knowledge
about personal  computers and  operating systems  such  as MS-DOS.  No
previous knowledge about Linux or UNIX is assumed.
  Despite this,  we strongly suggest that  UNIX novices invest in  one
of the many good UNIX books out there.  Several of them  are listed in
Appendix A.




                                  vi
                                                                   vii
_______________________________________________________________________

Organization

This book contains the following chapters.
  Chapter 1,  Introduction to Linux,  gives a general introduction  to
what Linux is, what it can do for you, and what is required  to run it
on your system.  It  also provides helpful hints for getting  help and
reducing overall stress.
  Chapter 2,  Obtaining and Installing Linux,  explains how to  obtain
the Linux software, as well as how to install it---from repartitioning
your drive,  creating filesystems,  and  loading the  software on  the
system.    It  contains  instructions  meant to  be  general  for  any
distribution of Linux,  and relies on  the documentation provided  for
your particular release to fill in any gaps.
  Chapter 3, Linux Tutorial,  is a complete introduction to  using the
Linux system for UNIX novices.  If you have  previous UNIX experience,
most of this material should be familiar.
  Chapter 4, System  Administration, introduces many of  the important
concepts of system  administration under  Linux.   This  will also  be
of interest to UNIX system  administrators who want to know  about the
Linux-specific issues of running a system.
  Chapter 5, Advanced Features,  introduces the reader to a  number of
advanced features supported by Linux, such as the X  Window System and
TCP/IP networking.   A  complete guide to  configuring XFree86-3.1  is
included.
  Appendix A,  Sources of  Linux Information,  is a  listing of  other
sources of  information  about Linux,  including  newsgroups,  mailing
lists, online documents, and books.
  Appendix B,  Linux Vendor List,  provides a  short list of  software
vendors offering Linux software and services.
  Appendix  C,  FTP  Tutorial  and  Site  List,   is  a  tutorial  for
downloading files  from  the Internet  with  FTP. This  appendix  also
includes a listing of FTP archive sites which carry Linux software.
  Appendix D, Linux BBS  List, is a listing of bulletin  board systems
worldwide which carry Linux software.  Because most Linux users are do
not have access to the Internet,  it is important that  information on
BBS systems becomes available.
  Appendix E,  The  GNU General  Public License,  contains  a copy  of
the GNU GPL, the license  agreement under which Linux is  distributed.
It is  very  important  that  Linux users  understand  the  GPL;  many
disagreements over the  terms of the  GPL have  been raised in  recent
months.


Acknowledgments

This book has been long in the making, and many people are responsible
for the  outcome.     In  particular,  I would  like  to  thank  Larry
Greenfield and  Karl Fogel  for their  work on  the  first version  of
Chapter 3, and to Lars  Wirzenius for his work  on Chapter 4.   Thanks
to Michael K. Johnson  for his assistance with  the LDP and the  LaTeX
                                                                  viii
_______________________________________________________________________

conventions used in this manual, and to Ed Chi, who sent  me a printed
copy of the book for edition.
  Thanks to Melinda A. McBride at SSC, Inc., who  did an excellent job
completing the index for Chapters 3, 4,  and 5.  I would also  like to
thank Andy Oram, Lar Kaufman, and Bill Hahn at O'Reilly and Associates
for their assistance with the Linux Documentation Project.
  Thanks to  Linux Systems Labs,  Morse Telecommunications,  Yggdrasil
Computing, and  others for their  support of  the Linux  Documentation
Project through sales of this book and other works.
  Much  thanks to  the many  activists,  including (in  no  particular
order) Linus Torvalds, Donald Becker,  Alan Cox, Remy Card,  Ted T'so,
H.J. Lu, Ross Biro, Drew Eckhardt,  Ed Carp, Eric Youngdale,  Fred van
Kempen, Steven Tweedie, and  a score of  others, for devoting so  much
time and energy to  this project, and  without whom there wouldn't  be
anything to write a book about.
  Special thanks to the myriad of readers who  have sent their helpful
comments and corrections.  There are  far too many to list here.   Who
needs a spell checker, when you have an audience?

                                                            Matt Welsh
                                                       13 January 1994


Credits and Legalese

The  Linux  Documentation  Project  is   a  loose  team  of   writers,
proofreaders, and editors who are working on a set of definitive Linux
manuals.  The overall coordinator of the project is Matt  Welsh, aided
by Lars Wirzenius and Michael K. Johnson.
  This  manual is  but  one in  a  set  of several  being  distributed
by the Linux  Documentation Project, including  a Linux User's  Guide,
System Administrator's  Guide,  and  Kernel  Hacker's Guide.     These
manuals are  all  available  in  LaTeX source  format  and  Postscript
output for  anonymous  FTP  from  sunsite.unc.edu,  in  the  directory
/pub/Linux/docs/LDP.
  We encourage anyone with  a penchant for writing or editing  to join
us in improving  Linux documentation.    If you  have Internet  e-mail
access, you can  join the DOC channel  of the Linux-Activists  mailing
list by sending mail to

    [e-mail]

with the line

    X-Mn-Admin:  join DOC

as the first line of the message body.
  Feel free to  get in touch with  the author and coordinator of  this
manual if you have questions, postcards, money, or ideas.   Matt Welsh
can be reached via Internet e-mail at [e-mail], and in real
                                                                    ix
_______________________________________________________________________

life at

    205 Gray Street
    Wilson, N.C. 27896
    U.S.A.
                                                                     x
_______________________________________________________________________

UNIX is a trademark of X/Open.
Linux is not a trademark, and has no connection to UNIXTM or X/Open.
The X Window System is  a trademark of the Massachusetts  Institute of
Technology.
MS-DOS and Microsoft Windows are trademarks of Microsoft, Inc.














Copyright cO1992--1994  Matt Welsh
205 Gray Street NE, Wilson NC, 27893 USA
[e-mail]

Linux  Installation  and  Getting   Started  may  be  reproduced   and
distributed, in whole or in part, subject to the following conditions:

0.  The copyright  notice above  and this  permission  notice must  be
    preserved complete on all complete or partial copies.

1.  Any translation  or  derivative  work of  Linux  Installation  and
    Getting Started must be approved  by the author in  writing before
    distribution.

2.  If you distribute Linux Installation and Getting Started  in part,
    instructions for  obtaining the  complete version  of this  manual
    must be included,  and a  means for  obtaining a complete  version
    provided.

3.  Small portions may be  reproduced as illustrations for reviews  or
    quotes in other  works without  this permission  notice if  proper
    citation is given.

4.  The GNU General Public License referenced below may  be reproduced
    under the conditions given within it.

5.  Several  sections  of  this  document  are  held   under  separate
    copyright.    When  these  sections are  covered  by  a  different
    copyright, the separate  copyright is  noted.   If you  distribute
    Linux Installation  and Getting  Started in  part,  and that  part
    is, in  whole,  covered under  a  separate, noted  copyright,  the
    conditions of that copyright apply.
                                                                    xi
_______________________________________________________________________

  Exceptions   to   these  rules   may   be   granted   for   academic
purposes:   Write  to Matt  Welsh,  at  the above  address,  or  email
[e-mail], and ask.  These restrictions are here  to protect
us as authors, not to restrict you as educators and learners.
  The author encourages  distributors of Linux software in  any medium
to use the  book as an  installation and new  user guide.   Given  the
copyright above, you are free  to print and distribute copies  of this
book with your software.  You may either distribute this  book free of
charge, or for profit.  If  doing so, you may wish to include  a short
``installation supplement'' for your release.
  The  author  would  like  to  know  of  any  plans  to  publish  and
distribute this book commercially.   In this  way, we can ensure  that
you are kept up-to-date with new revisions.  And, should a new version
be right around the corner,  you might wish to delay  your publication
of the book until it is available.
  If  you   are  distributing  this   book  commercially,   donations,
royalties,  and/or printed  copies  are  greatly  appreciated  by  the
author.  Contributing in this way shows your support for free software
and the Linux Documentation Project.

All source code in  Linux Installation and  Getting Started is  placed
under the GNU General Public  License.  See  Appendix E for a copy  of
the GNU ``GPL.''


Documentation Conventions

These conventions should be obvious,  but we'll include them  here for
the pedantic.

Bold       Used  to mark  new concepts,  WARNINGS, and  keywords in  a
           language.

italics    Used for  emphasis in text, and occasionally for  quotes or
           introductions at the beginning of a section.   Also used to
           indicate commands for the user to  type when showing screen
           interaction (see below).
<slanted>  Used  to mark  meta-variables in  the text,  especially  in
           representations of the command line.  For example,


               ls -l <foo>

           where  <foo>  would  ``stand  for''  a  filename,  such  as
           /bin/cp.

Typewriter Used to represent screen interaction, as in


               $ ls --l /bin/cp
               -rwxr-xr-
                                                                   xii
_______________________________________________________________________

               x  1 root    wheel    12104 Sep 25 15:53 /bin/cp


           Also used for code examples, whether it  is C code, a shell
           script,  or something else,  and to display general  files,
           such as configuration files.   When necessary for clarity's
           sake,  these examples or figures  will be enclosed in  thin
           boxes.
[Key]      Represents a key  to press.  You will often see it  in this
           form:


               Press [return] to continue.

!          A  diamond in the  margin, like  a black  diamond on a  ski
           hill,  marks ``danger''  or ``caution.''   Read  paragraphs
           marked this way carefully.








Chapter 1




Introduction to Linux



Linux is  quite  possibly  the  most  important  achievement  of  free
software since the original Space War,  or, more recently, Emacs.   It
has developed into the operating system for businesses, education, and
personal productivity.  Linux is  no longer just for UNIX  wizards who
sit for hours in front of the glowing console (although  we assure you
that quite a number of users fall into this category).  This book will
help you get the most out of it.
  Linux  (pronounced with  a short  i,  as in  LIH-nucks)  is a  clone
of the  UNIX operating  system  that runs  on  Intel 80386  and  80486
computers.    It  supports a  wide  range  of software,  from  TeX  to
X Windows to the GNU C/C++ compiler to TCP/IP.  It's a versatile, bona
fide implementation of UNIX,  freely distributed by  the terms of  the
GNU General Public License (see Appendix E).
  Linux can  turn any  386 or  486 PC  into a  workstation.   It  will
give you the full power  of UNIX at your  fingertips.  Businesses  are
installing Linux on entire networks  of machines, using the  operating
system to manage  financial and hospital  records, a distributed  user
computing environment,  telecommunications, and  more.    Universities
worldwide are using  Linux for teaching  courses on operating  systems
programming and  design.     And,  of  course,  computing  enthusiasts
everywhere are using Linux at home, for programming, productivity, and
all-around hacking.
  What makes Linux  so different is that  it is a free  implementation
of UNIX.  It was  and still  is developed  by a  group of  volunteers,
primarily on the Internet, exchanging code, reporting bugs, and fixing
problems in an open-ended environment.   Anyone is welcome to  join in
the Linux development effort:  all  it takes is interest in  hacking a
free UNIX clone and some kind of programming know-how.   The book that
you hold in your hands is your tour guide.

1.1 About This Book

This book  is  an installation  and  entry-level  guide to  the  Linux
system.   The purpose  is to  get new users  up and  running with  the
system by consolodating  as much important  material as possible  into


                                  1
1.1.   About This Book                                               2
_______________________________________________________________________

one book.  Instead of covering many of the volatile technical details,
those things which tend to change with rapid development,  we give you
enough background to find out more on your own.
  Linux is  not difficult to install  and use.   However, as with  any
implementation of UNIX, there  is often some  black magic involved  to
get everything working correctly.  We hope that this book will get you
on the Linux tourbus and show you how groovy this operating system can
be.
  In this book, we cover the following topics.

 o  What is Linux?  The design and philosophy of this unique operating
    system, and what it can do for you.

 o  All of  the details  of what  is needed  to run  Linux,  including
    suggestions on what kind of hardware configuration  is recommended
    for a complete system.

 o  How to obtain  and install Linux.    There are many  distributions
    of  the  Linux  software.     We  present  a   general  discussion
    of  Linux  software  distributions,   how  to  obtain  them,   and
    generic instructions for installing the software (which  should be
    applicable to any distribution).

    This edition also contains specific instructions for the Slackware
    distribution of Linux.

 o  A brief introductory UNIX tutorial, for those users who have never
    had experience with UNIX before.  This tutorial should, hopefully,
    provide enough material for complete novices to have  enough basic
    know-how to find their way around the system.

 o  An introduction to systems administration with Linux.  This covers
    the most important tasks  that new Linux administrators will  need
    to be familiar with, such as creating users, managing filesystems,
    and so forth.

 o  Information on configuring  more advanced aspects  of Linux,  such
    as the X Window System,  networking with TCP/IP and SLIP,  and the
    setup of electronic mail and news systems.

  This book is for  the personal computer user wishing to  get started
with Linux.  We don't  assume previous UNIX experience, but  do expect
novices to  refer  to  other materials  along  the  way.    For  those
unfamiliar with UNIX, a list of useful sources of information is given
in Appendix A.  In general,  this book is meant to be read  along with
another book on basic UNIX concepts.
1.2.   A Brief History of Linux                                      3
_______________________________________________________________________

1.2 A Brief History of Linux

UNIX is one of the most popular operating systems worldwide because of
its large support base and distribution.  It was  originally developed
as a  multitasking  system for  minicomputers  and mainframes  in  the
mid-1970's, but has since grown to become one of the  most widely used
operating systems anywhere, despite its sometimes  confusing interface
and lack of central standardization.
  The real  reason  for UNIX's  popularity?   Many  hackers feel  that
UNIX is the Right Thing---the One  True Operating System.  Hence,  the
development of Linux by an expanding group of UNIX hackers who want to
get their hands dirty with their own system.
  Versions  of UNIX  exist for  many  systems---ranging from  personal
computers to supercomputers such as the  Cray Y-MP.  Most  versions of
UNIX for personal computers  are quite expensive  and cumbersome.   At
the time of this writing, a one-machine version of AT&T's System V for
the 386 runs at about US$1500.
  Linux is a freely distributable version of  UNIX developed primarily
by Linus Torvalds (1) at the University of Helsinki in Finland.  Linux
was developed  with the  help  of many  UNIX programmers  and  wizards
across the Internet, allowing anyone with enough know-how and gumption
the ability  to develop  and  change the  system.    The Linux  kernel
uses no code from  AT&T or any other  proprietary source, and much  of
the software available for  Linux is developed  by the GNU project  at
the Free Software  Foundation in Cambridge,  Massachusetts.   However,
programmers all over the world have contributed to the growing pool of
Linux software.
  Linux  was  originally  developed  as  a  hobby   project  by  Linus
Torvalds.   It was inspired  by Minix, a  small UNIX system  developed
by Andy Tanenbaum,  and   the first  discussions about  Linux were  on
the USENET newsgroup comp.os.minix.  These discussions  were concerned
mostly with the development of a small, academic UNIX system for Minix
users who wanted more.
  The very  early development  of Linux  was mostly  dealing with  the
task-switching features  of the  80386 protected-mode  interface,  all
written in assembly code.  Linus writes,

     ``After that it  was plain sailing:  hairy coding still,  but
    I had some devices, and debugging was easier.  I started using
    C at  this stage,  and it  certainly  speeds up  developement.
    This is also when I start to get serious about my megalomaniac
    ideas to make `a better Minix  than Minix'.  I was  hoping I'd
    be able to recompile gcc under Linux some day...
     ``Two months for  basic setup, but then only slightly  longer
    until I had  a disk-driver (seriously  buggy, but it  happened
    to work  on my  machine) and  a small  filesystem.   That  was
    about when I made 0.01 available [around late August of 1991]:

----------------------------
 1. [e-mail].
1.2.   A Brief History of Linux                                      4
_______________________________________________________________________

    it wasn't pretty,  it had  no floppy driver,  and it  couldn't
    do much anything.   I don't  think anybody ever compiled  that
    version.  But by  then I was hooked,  and didn't want to  stop
    until I could chuck out Minix.''

  No  announcement  was  ever made  for  Linux  version  0.01.     The
0.01 sources weren't even  executable:  they  contained only the  bare
rudiments of the kernel source, and  assumed that you had access  to a
Minix machine to compile and play with them.
  On 5  October 1991, Linus  announced the first ``official''  version
of Linux, version 0.02.   At  this point, Linus  was able to run  bash
(the GNU Bourne  Again Shell) and  gcc (the GNU  C compiler), but  not
very much else was working.   Again,  this was intended as a  hacker's
system.  The primary focus was kernel development---none of the issues
of user support, documentation, distribution, and so on had  even been
addressed.   Today, the  Linux community  still seems  to treat  these
ergonomic issues  as secondary  to  the ``real  programming''---kernel
development.
  Linus wrote in comp.os.minix,

     ``Do you pine for  the nice days of Minix-1.1, when  men were
    men and wrote  their own device  drivers?   Are you without  a
    nice project and just dying to cut your teeth on a  OS you can
    try to modify for your needs?  Are you finding  it frustrating
    when everything works on Minix?  No more all-nighters to get a
    nifty program working?  Then this post might be just for you.
     ``As  I  mentioned  a  month  ago,  I'm  working  on  a  free
    version of a  Minix-lookalike for  AT-386 computers.   It  has
    finally reached the stage where  it's even usable (though  may
    not be  depending on  what  you want),  and  I am  willing  to
    put out  the sources  for  wider distribution.    It  is  just
    version 0.02...but I've successfully  run bash, gcc, gnu-make,
    gnu-sed, compress, etc.  under it.''

  After version 0.03, Linus  bumped the version number up to  0.10, as
more people started  to work  on the  system.   After several  further
revisions, Linus increased the version number to 0.95, to  reflect his
expectation that  the system  was ready  for  an ``official''  release
very soon.   (Generally, software is  not assigned the version  number
1.0 until it  is theoretically  complete or  bug-free.)   This was  in
March of 1992.   Almost a year and a  half later, in late  December of
1993, the Linux kernel was still at version 0.99.pl14---asymptotically
approaching 1.0.  As of  the time of this writing, the  current kernel
version is 1.1 patchlevel 52, and 1.2 is right around the corner.
  Today,  Linux  is   a  complete  UNIX  clone,  capable   of  running
X Windows,  TCP/IP, Emacs,  UUCP,  mail and  news software,  you  name
it.  Almost all of  the major free software packages have  been ported
to Linux, and commercial  software is becoming  available.  Much  more
hardware is supported than in original  versions of the kernel.   Many
people have  executed  benchmarks on  80486  Linux systems  and  found
1.3.   System Features                                               5
_______________________________________________________________________

them comparable with mid-range workstations from Sun  Microsystems and
Digital Equipment Corporation.  Who would have ever guessed  that this
``little'' UNIX clone would have grown up to take on  the entire world
of personal computing?


1.3 System Features

Linux supports most of the features found in other  implementations of
UNIX, plus quite a few that aren't found elsewhere.  This section is a
nickel tour of the Linux kernel features.
  Linux is a  complete multitasking, multiuser operating  system (just
like all  other versions  of UNIX).  This means  that  many users  can
be logged into  the same  machine at once,  running multiple  programs
simultaneously.
  The  Linux  system  is mostly  compatible  with  a  number  of  UNIX
standards (inasmuch  as  UNIX  has  standards) on  the  source  level,
including IEEE  POSIX.1,  System V,  and  BSD features.        It  was
developed with source portability  in mind:   therefore, you are  most
likely to find commonly-used  features in the  Linux system which  are
shared across multiple  implementations.   A great  deal of free  UNIX
software available on  the Internet  and elsewhere  compiles on  Linux
out of the box.   In addition, all  source code for the Linux  system,
including the kernel,  device drivers, libraries,  user programs,  and
development tools, is freely distributable.
  Other  specific  internal  features  of  Linux   include  POSIX  job
control (used by shells  such as csh  and bash), pseudoterminals  (pty
devices), and  support  for  national or  customized  keyboards  using
dynamically-loadable keyboard drivers.    Linux also supports  virtual
consoles, which allow  you to switch  between multiple login  sessions
from the system console in text mode.  Users of the ``screen'' program
will find the Linux virtual console implementation familiar.
  The kernel is able  to emulate 387-FPU instructions itself,  so that
systems without  a  math coprocessor  can  run programs  that  require
floating-point math instructions.
  Linux supports various filesystem  types for storing data.   Various
filesystems,  such as  the  ext2fs  filesystem,  have  been  developed
specifically for Linux.  Other  filesystem types, such as  the Minix-1
and Xenix filesystems, are also supported.  The  MS-DOS filesystem has
been implemented as well, allowing you to access MS-DOS  files on hard
drive or floppy directly.  The ISO 9660 CD-ROM filesystem  type, which
reads all standard formats of CD-ROMs, is also supported.   We'll talk
more about filesystems in Chapters 2 and 4.
  Linux  provides  a complete  implementation  of  TCP/IP  networking.
This includes device  drivers for  many popular  Ethernet cards,  SLIP
(Serial Line  Internet  Protocol,  allowing  you to  access  a  TCP/IP
network via  a  serial  connection),   PLIP  (Parallel  Line  Internet
Protocol), PPP (Point-to-Point Protocol),  NFS (Network File  System),
and so on.    The complete  range of  TCP/IP clients  and services  is
supported, such as FTP, telnet, NNTP, and SMTP. We'll  talk more about
networking in Chapter 5.
1.4.   Software Features                                             6
_______________________________________________________________________

  The Linux  kernel  is developed  to use  the special  protected-mode
features of the  Intel 80386  and 80486  processors.   In  particular,
Linux  makes  use  of   the  protected-mode  descriptor-based   memory
management paradigm and many of  the other advanced features of  these
processors.   Anyone  familiar with  80386 protected-mode  programming
knows that this chip  was designed for  a multitasking system such  as
UNIX (or, actually, Multics).  Linux exploits this functionality.
  The Linux  kernel supports  demand-paged loaded executables.    That
is, only  those segments  of a  program  which are  actually used  are
read into memory  from disk.    Also, copy-on-write  pages are  shared
among executables, meaning that if several instances of a  program are
running at once, they  will share pages  in physical memory,  reducing
overall memory usage.
  In order  to increase  the amount  of available  memory, Linux  also
implements disk  paging:   that  is,  up to  256 megabytes  of  ``swap
space''(2) can  be  allocated on  disk.    When  the  system  requires
more physical memory, it  will swap out  inactive pages to disk,  thus
allowing you  to run  larger applications  and support  more users  at
once.  However,  swap is no substitute  for physical RAM---it is  much
slower due to drive access latency times.
  The kernel also implements  a unified memory pool for  user programs
and disk cache.  In this way, all free memory is used for caching, and
the cache is reduced when running large programs.
  Executables use  dynamically linked shared  libraries, meaning  that
executables share common library code  in a single library file  found
on disk, not unlike the SunOS  shared library mechanism.   This allows
executable files to occupy much  less space on disk,  especially those
that use many  library functions.   There  are also  statically-linked
libraries for  those who  wish  to use  object debugging  or  maintain
``complete'' executables without the need  for shared libraries to  be
in place.  Linux shared libraries are dynamically linked  at run-time,
allowing the programmer to replace modules of the libraries with their
own routines.
  To  facilitate debugging,  the  Linux  kernel  does core  dumps  for
post-mortem analysis.  Using a core dump and an executable linked with
debugging support, it is possible  to determine what caused  a program
to crash.


1.4 Software Features

In this  section,   we'll  introduce  you  to  many  of  the  software
applications available for Linux,  and talk about  a number of  common
computing tasks.  After all, the most important part of  the system is
----------------------------
 2. Swap space  is inappropriately  named:  entire  processes are  not
swapped, but rather individual pages.  Of course, in many cases entire
processes will be swapped out, but this is not neccessarily always the
case.
1.4.   Software Features                                             7
_______________________________________________________________________

the wide range of software  available for it.   The fact that most  of
this software is freely distributable is even more impressive.

1.4.1 Basic commands and utilities

Virtually every  utility that  you would  expect to  find on  standard
implementations of UNIX has been ported to Linux.  This includes basic
commands such as ls,  awk, tr,  sed, bc, more,  and so on.   You  name
it, Linux has  it.   Therefore, you can  expect your familiar  working
environment on other  UNIX systems  to be  duplicated on Linux.    All
of the  standard commands  and utilities  are there.    (Novice  Linux
users should see  Chapter 3 for  an introduction  to these basic  UNIX
commands.)
  Many text editors  are available, including vi,  ex, pico, jove,  as
well as GNU Emacs and variants such as Lucid Emacs (which incorporates
extensions for use  under X Windows)  and joe.   Whatever text  editor
you're accustomed to using has more than likely been ported  to Linux.

  The choice of a text editor is an interesting one.   Many UNIX users
still use ``simple''  editors such as  vi (in  fact, the author  wrote
this book using vi  under Linux).   However, vi has many  limitations,
due to  its  age,  and  more  modern (and  complex)  editors  such  as
Emacs are gaining popularity.   Emacs  supports a complete  LISP-based
macro language and interpreter, a  powerful command syntax, and  other
fun-filled extensions.   Emacs macro  packages exist  to allow you  to
read electronic  mail  and news,  edit  the contents  of  directories,
and even engage in  an artificially intelligent psychotherapy  session
(indispensible for stressed-out Linux hackers).
  One  interesting note  is that  most of  the  basic Linux  utilities
are GNU software.   These GNU utilities support advanced  features not
found in the standard  versions from BSD  or AT&T. For example,  GNU's
version of the vi editor, elvis, includes a structured  macro language
which differs from  the original  AT&T implementation.   However,  the
GNU utilities strive to remain compatible with their BSD and  System V
counterparts.  Many people consider the GNU versions of these programs
superior to the originals.
  The  most important  utility  to  many users  is  the  shell.    The
shell is  a  program  which  reads  and  executes  commands  from  the
user.  In addition, many  shells provide features such as  job control
(allowing the user to manage  several running processes at  once---not
as Orwellian  as  it sounds),  input  and output  redirection,  and  a
command language for writing shell scripts.  A shell script  is a file
containing a program  in the  shell command language,  analogous to  a
``batch file'' under MS-DOS.
  There are  many  types of  shells available  for Linux.    The  most
important difference  between shells  is the  command language.    For
example, the C Shell (csh)  uses a command language somewhat  like the
C programming language.   The  classic Bourne  Shell uses a  different
command language.   One's  choice of  a shell  is often  based on  the
command language that it provides.  The shell that you use defines, to
1.4.   Software Features                                             8
_______________________________________________________________________

some extent, your working environment under Linux.
  No matter what  shell you're accustomed to,  some version of it  has
probably been ported  to Linux.   The  most popular  shell is the  GNU
Bourne Again Shell (bash), a Bourne shell variant which  includes many
advanced features, such as job  control, command history, command  and
filename completion, an Emacs-like  interface for editing the  command
line, and powerful extensions  to the standard Bourne shell  language.
Another popular shell is tcsh, a version of the C  Shell with advanced
functionality similar to  that found in  bash.   Other shells  include
zsh, a small Bourne-like shell;  the Korn shell (ksh); BSD's ash;  and
rc, the Plan 9 shell.
  What's so important  about these basic utilities?   Linux gives  you
the unique opportunity to tailor a  custom system to your needs.   For
example, if  you're the  only person  who uses  your  system, and  you
prefer to  exclusively use  the vi  editor,  and bash  as your  shell,
there's no reason to  install other editors  or shells.   The ``do  it
yourself'' attitude is prevalent among Linux hackers and users.

1.4.2 Text processing and word processing

Almost every  computer user  has  a need  for  some kind  of  document
preparation system.   (How many computer  enthusiasts do you know  who
still use pen and paper?   Not many, we'll  wager.)  In the  PC world,
word processing is  the norm:   it involves  editing and  manipulating
text (often  in  a ``What-You-See-Is-What-You-Get''  environment)  and
producing printed copies of the  text, complete with figures,  tables,
and other garnishes.
  In  the UNIX  world,  text processing  is  much more  common,  which
is quite  different than  the classical  concept  of word  processing.
With a text  processing system, text  is entered  by the author  using
a ``typesetting language'',  which describes  how the  text should  be
formatted.    Instead of  entering  the  text within  a  special  word
processing environment,  the  source may  be  modified with  any  text
editor such as vi or Emacs.  Once the source text  (in the typesetting
language) is  complete, the  user  formats the  text  with a  separate
program, which converts the source to a format suitable  for printing.
This is somewhat analogous to programming in a language such as C, and
``compiling'' the document into a printable form.
  There are many text processing systems available for Linux.   One is
groff, the GNU version of the classic nroff text  formatter originally
developed by Bell Labs and still used on many UNIX  systems worldwide.
Another modern  text processing  system is  TeX,  developed by  Donald
Knuth of computer science fame.   Dialects of TeX, such as  LaTeX, are
also available.
  Text processors such  as TeX and groff  differ mostly in the  syntax
of their formatting languages.   The  choice of one formatting  system
over another  is  also based  upon  what  utilities are  available  to
satisfy your needs, as well as personal taste.
  For example, some  people consider the groff formatting  language to
be a bit obscure, so they  use TeX, which is more readable  by humans.
1.4.  Software Features                                              9
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However, groff is capable of producing plain ASCII output, viewable on
a terminal, while TeX is  intended primarily for output to  a printing
device.  However, various  programs exist to produce plain  ASCII from
TeX-formatted documents, or to convert TeX to groff, for example.
  Another text processing system is texinfo, an extension  to TeX used
for software documentation by the  Free Software Foundation.   texinfo
is capable of  producing a  printed document,  or an  online-browsable
hypertext ``Info'' document from a single source file.  Info files are
the main format of documentation used by GNU software such as Emacs.
  Text  processors are  used  widely in  the computing  community  for
producing papers, theses, magazine articles, and books (in  fact, this
book was  produced using  LaTeX). The  ability to  process the  source
language as  a plain  text  file opens  the  door to  many  extensions
to the  text processor  itself.    Because  source documents  are  not
stored in  an  obscure format,  readable  only  by a  particular  word
processor, programmers are able  to write parsers and translators  for
the formatting language, extending the system.
  What  does such  a  formatting language  look  like?    In  general,
the formatting language  source consists  mostly of  the text  itself,
along with ``control codes'' to  produce a particular effect,  such as
changing fonts, setting margins, creating lists, and so on.
  As an example, take the following text:

    Mr.  Torvalds:

    We are  very  upset  with  your  current  plans  to  implement
    post-hypnotic suggestion in  the Linux  terminal driver  code.
    We feel this way for three reasons:


    1.  Planting subliminal messages in the terminal driver is not
        only immoral, it is a waste of time;

    2.  It has been proven that ``post-hypnotic  suggestions'' are
        ineffective when used upon unsuspecting UNIX hackers;

    3.  We have already implemented high-voltage electric  shocks,
        as a security measure, in the code for login.


    We hope you will reconsider.

  This  text would  appear in  the LaTeX  formatting  language as  the
following:

    \begin{quote}
    Mr. Torvalds:

    We are very upset with your current plans to  implement {\em post-
    hypnotic
1.4.   Software Features                                            10
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    suggestion\/}      in      the       {\bf      Linux}       termi-
    nal driver code. We feel this
    way for three reasons:
    \begin{enumerate}
    \item    Planting    subliminal     messages    in    the     ker-
    nel driver is not only
          immoral, it is a waste of time;
    \item  It   has   been   proven   that   ``post-hypnotic   sugges-
    tions'' are ineffective
          when used upon unsuspecting UNIX hackers;
    \item   We   have    already   implemented   high-voltage    elec-
    tric shocks, as a
          security measure, in the code for {\tt login}.
    \end{enumerate}
    We hope you will reconsider.
    \end{quote}

  The author enters the  above ``source'' text using any  text editor,
and generates  the  formatted output  by  processing the  source  with
LaTeX. At  first glance,  the typesetting  language may  appear to  be
obscure, but  it's  actually  quite easy  to  learn.    Using  a  text
processing system enforces typographical standards when writing.   For
example, all enumerated  lists within a document  will look the  same,
unless the  author  modifies the  definition  of the  enumerated  list
``environment''.    The  primary  goal  is  to  allow  the  author  to
concentrate on  writing the  actual text,  instead  of worrying  about
typesetting conventions.
  WYSIWYG  word  processors are  attractive  for  many  reasons;  they
provide a  powerful  (and  sometimes  complex)  visual  interface  for
editing the document.   However, this interface is  inherently limited
to those aspects of text layout which are accessible to the user.  For
example, many word  processors provide  a special ``format  language''
for producing complicated expressions  such as mathematical  formulae.
This is identical text processing, albeit on a much smaller scale.
  The subtle benefit of text processing is that  the system allows you
to specify exactly what you mean.  Also, text processing systems allow
you to edit the source  text with any text  editor, and the source  is
easily converted to other formats.  The tradeoff for  this flexibility
and power is the lack of a WYSIWYG interface.
  Many  users of  word processors  are used  to  seeing the  formatted
text as they edit  it.  On  the other hand,  when writing with a  text
processor, one generally does not worry about how the text will appear
when formatted.  The writer learns to expect how the  text should look
from the formatting commands used in the source.
  There are programs  which allow you  to view the formatted  document
on a graphics display before printing.  For example,  the xdvi program
displays a ``device  independent'' file  generated by  the TeX  system
under the X Windows  environment.   Other software applications,  such
as xfig,  provide a  WYSIWYG graphics  interface  for drawing  figures
and diagrams, which are subsequently converted to the  text processing
1.4.   Software Features                                            11
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language for inclusion in your document.
  Admittedly, text  processors such as  nroff were around long  before
word processing was available.   However, many people still  prefer to
use text processing, because it  is more versatile and  independent of
a graphics environment.   In either case,  the idoc word processor  is
also available for Linux, and before long we expect  to see commercial
word processors becoming available as  well.  If you  absolutely don't
want to give up  word processing for  text processing, you can  always
run MS-DOS, or some other operating system, in addition to Linux.
  There are  many other  text-processing-related utilities  available.
The powerful METAFONT  system, used  for designing fonts  for TeX,  is
included with the Linux  port of TeX.  Other programs include  ispell,
an interactive  spell  checker  and  corrector;  makeindex,  used  for
generating indicies in  LaTeX documents;  as  well as  many groff  and
TeX-based macro packages  for formatting many  types of documents  and
mathematical texts.  Conversion  programs to translate between TeX  or
groff source to a myriad of other formats are available.

1.4.3 Programming languages and utilities

Linux provides a complete UNIX programming environment,  including all
of the standard libraries, programming tools, compilers, and debuggers
that you would expect to find on other UNIX systems.   Within the UNIX
software development world,  applications and  systems programming  is
usually done in C or C++.   The standard C and C++ compiler  for Linux
is GNU's gcc, which  is an advanced,  modern compiler supporting  many
options.   It is  also capable  of compiling C++  (including AT&T  3.0
features) as well as  Objective-C, another object-oriented dialect  of
C.
  Besides C and  C++, many other compiled and  interpreted programming
languages have  been ported  to  Linux,  such as  Smalltalk,  FORTRAN,
Pascal,  LISP, Scheme,   and Ada  (if  you're  masochistic  enough  to
program in Ada---we're not going to  stop you).  In addition,  various
assemblers for writing protected-mode 80386 code are available, as are
UNIX hacking favorites such  as Perl (the  script language to end  all
script languages) and Tcl/Tk  (a shell-like command processing  system
including support for developing simple X Windows applications).
  The advanced  gdb  debugger has  been ported,  which  allows you  to
 step through  a program  to find  bugs, or  examine the  cause for  a
crash using  a core  dump.    gprof, a  profiling utility,  will  give
you performance statistics  for your program,  letting you know  where
your program is spending most of  its time executing.  The  Emacs text
editor provides an interactive editing and compilation environment for
various programming  languages.    Other tools  include GNU  make  and
imake, used to manage  compilation of large  applications; and RCS,  a
system for source locking and revision control.
  Linux implements  dynamically-linked shared  libraries, which  allow
binaries to  be much  smaller  as the  subroutine  code is  linked  at
run-time.  These DLL libraries also allow the  applications programmer
to override  function definitions with  their own code.   For example,
1.4.   Software Features                                            12
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if a  programmer wished  to  write her  own  version of  the  malloc()
library routine,  the linker would  use the  programmer's new  routine
instead of the one found in the libraries.
  Linux is  ideal for  developing UNIX  applications.   It provides  a
modern programming environment  with all  of the  bells and  whistles.
Various standards  such as  POSIX.1 are  supported, allowing  software
written for Linux to be easily ported to other systems.   Professional
UNIX programmers and  system administrators can  use Linux to  develop
software at home, and  then transfer the  software to UNIX systems  at
work.   This not only  can save a  great deal of  time and money,  but
will also let you work in the  comfort of your own home.(3)   Computer
Science students  can  use Linux  to  learn  UNIX programming  and  to
explore other aspects of the system, such as kernel architecture.
  With Linux,  not only  do you  have access  to the  complete set  of
libraries and programming  utilities, but you  also have the  complete
kernel and library source code at your fingertips.

1.4.4 The X Window System

The X  Window  System is  the  standard  graphics interface  for  UNIX
machines.  It is a powerful environment supporting  many applications.
Using X Windows, the  user can have  multiple terminal windows on  the
screen at once,  each one  containing a  different login session.    A
pointing device such as  a mouse is often  used with the X  interface,
although it isn't required.
  Many  X-specific applications  have  been written,  such  as  games,
graphics utilities, programming  and documentation tools,  and so  on.
With Linux and X,  your system is  a bona fide  workstation.   Coupled
with TCP/IP networking,  you can even  display X applications  running
on other machines  on your Linux  display, as  is possible with  other
systems running X.
  The X Window System  was originally developed at MIT, and  is freely
distributable.    However,  may commercial  vendors  have  distributed
proprietary enhancements  to the  original X  Windows software.    The
version of X Windows available for  Linux is known as XFree86,  a port
of X11R5 made freely distributable  for 80386-based UNIX systems  such
as Linux.  XFree86 supports a wide range of video  hardware, including
VGA, Super VGA, and a number  of accelerated video adaptors.   This is
a complete distribution of  the X Windows  software, containing the  X
server itself, many applications and utilities, programming libraries,
and documentation.
  Standard X applications include xterm (a terminal  emulator used for
most text-based applications within an  X window); xdm (the  X Session
Manager, which handles logins); xclock (a simple clock  display); xman
(an X-based  man page  reader), and  more.   The  many X  applications

----------------------------
 3. The author  uses his Linux  system to develop  and test X  Windows
applications at home, which  can be directly compiled on  workstations
elsewhere.
1.4.   Software Features                                            13
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available for Linux  are too numerous  to mention  here, but the  base
XFree86 distribution includes the  ``standard'' applications found  in
the original MIT release.   Many others are available separately,  and
theoretically any  application written  for X  Windows should  compile
cleanly under Linux.
  The look  and feel  of the X  Windows interface  is controlled to  a
large extent  by the  window manager.    This friendly  program is  in
charge of the placement of  windows, the user interface  for resizing,
iconifying, and moving windows,  the appearance of window frames,  and
so on.   The standard XFree86  distribution includes twm, the  classic
MIT window manager, although more advanced window managers such as the
Open Look Virtual Window Manager (olvwm)  are available as well.   One
window manager that is  popular among Linux  users is fvwm.   This  is
a small window manager,  requiring less than  half of the memory  used
by twm.  It provides a  3-D appearance for windows, as well  a virtual
desktop---if the user moves the mouse  to the edge of the screen,  the
entire desktop is shifted as if  the display were much larger  than it
actually is.  fvwm is  greatly customizable, and allows  all functions
to be accessed from  the keyboard as  well as the  mouse.  Many  Linux
distributions use fvwm as the standard window manager.
  The XFree86 distribution contains programming libraries  and include
files for those wily programmers  who wish to develop X  applications.
Various widget  sets,  such  as  Athena,  Open  Look,  and  Xaw3D  are
supported.    All of  the  standard fonts,  bitmaps,  man  pages,  and
documentation are  included.   PEX  (a programming  interface for  3-D
graphics) is also supported.
  Many X  applications programmers  use the  proprietary Motif  widget
set for development.   Several vendors  sell single and  multiple-user
licenses  for  a  binary  version  of  Motif  for  Linux.      Because
Motif itself is  relatively expensive,  not many Linux  users own  it.
However, binaries statically linked with Motif routines may  be freely
distributed.  Therefore, if you  write a program using Motif  and wish
to distribute  it freely,  you  may  provide a  binary so  that  users
without Motif can use the program.
  The only major  caveats with X Windows  are the hardware and  memory
requirements.  A  386 with 4  megabytes of RAM  is capable of  running
X, but  8 megabytes  or more  of physical  RAM are  needed  to use  it
comfortably.  A faster processor  is nice to have as well,  but having
enough physical RAM is much more  important.  In addition,  to achieve
really slick video  performance, an  accelerated video  card (such  as
a local bus  S3-chipset card)  is strongly recommended.    Performance
ratings in excess  of 140,000  xstones have been  acheived with  Linux
and XFree86.    With  sufficient hardware,  you'll  find that  running
X and  Linux is  as fast,  or faster,  than  running X  on other  UNIX
workstations.
  In Chapter 5 we'll discuss how to install and use X on your system.
1.4.   Software Features                                            14
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1.4.5 Networking

Interested in  communicating with  the world?    Yes?    No?    Maybe?
Linux supports the two primary networking protocols for  UNIX systems:
TCP/IP  and  UUCP.  TCP/IP  (Transmission   Control  Protocol/Internet
Protocol, for acronym aficionados) is the set of  networking paradigms
that allow  systems all  over the  world to  communicate  on a  single
network known as the Internet.   With Linux, TCP/IP, and  a connection
to the network, you can communicate with users and machines across the
Internet via electronic  mail, USENET news,  file transfers with  FTP,
and more.  There are many Linux systems currently on the Internet.
  Most  TCP/IP   networks  use  Ethernet   as  the  physical   network
transport.  Linux supports many popular Ethernet cards  and interfaces
for personal computers, including  the D-Link pocket Ethernet  adaptor
for laptops.
  However, because  not everyone has an  Ethernet drop at home,  Linux
also supports SLIP (Serial Line Internet Protocol), which allows   you
to connect to the Internet  via modem.   In order to use SLIP,  you'll
need to  have access  to a  SLIP server,  a machine  connected to  the
network which allows dial-in access.  Many businesses and universities
provide such SLIP  servers.   In  fact, if  your Linux  system has  an
Ethernet connection as well as a modem, you can configure it as a SLIP
server for other hosts.
  NFS (Network  File System)  allows your system  to seamlessly  share
files with  other  machines  on  the  network.    FTP  (File  Transfer
Protocol) allows you to transfer files between other machines.   Other
applications include  sendmail,  a system  for sending  and  receiving
electronic mail using  the SMTP protocol;  NNTP-based electronic  news
systems such as C-News and INN;  telnet, rlogin, and rsh,  which allow
you to login and  execute commands on  other machines on the  network;
and finger,  which allows  you to  get information  on other  Internet
users.   There  are literally  tons of  TCP/IP-based applications  and
protocols out there.
  The full  range of mail  and news readers  are available for  Linux,
such as elm, pine, rn, nn, and tin.  Whatever your preference, you can
configure your Linux system  to send and  receive electronic mail  and
news from all over the world.
  If  you have  experience  with  TCP/IP applications  on  other  UNIX
systems, Linux will be  very familiar to you.   The system provides  a
standard socket programming interface, so virtually any  program which
uses TCP/IP can be ported to Linux.  The Linux X  server also supports
TCP/IP, allowing you to display applications running on  other systems
on your Linux display.
  In  Chapter 5  we'll  discuss  configuration and  setup  of  TCP/IP,
including SLIP, for Linux.
  UUCP (UNIX-to-UNIX  Copy)  is an  older mechanism  used to  transfer
files, electronic  mail, and  electronic news  between UNIX  machines.
Classically, UUCP  machines connected  to each  other  over the  phone
lines via modem, but UUCP is  able to transport over a  TCP/IP network
as well.   If you do  not have access  to a TCP/IP  network or a  SLIP
1.4.   Software Features                                            15
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server, you can configure  your system to  send and receive files  and
electronic mail using UUCP. See Chapter 5 for more information.

1.4.6 Telecommunications and BBS software

If you  have a  modem,  you will  be able  to  communicate with  other
machines using one  of the  telecommunications packages available  for
Linux.  Many people use telecommunications software to access bulletin
board systems (BBSs),  as well as commercial  online services such  as
Prodigy, CompuServe,  and America  On-Line.   Other  people use  their
modems to  connect to  a UNIX  system  at work  or school.    You  can
even use your modem and  Linux system to send and  receive facsimiles.
Telecommunications software under Linux is very similar to  that found
under MS-DOS or other operating systems.   Anyone who has ever  used a
telecommunications package will find the Linux equivalent familiar.
  One  of  the  most popular  communications  packages  for  Linux  is
Seyon, an X application providing a customizable, ergonomic interface,
with built-in  support for  various file  transfer  protocols such  as
Kermit, ZModem, and so on.  Other telecommunications  programs include
C-Kermit, pcomm,  and minicom.   These  are similar to  communications
programs found on other operating systems, and are quite easy to use.
  If  you do  not  have access  to a  SLIP  server (see  the  previous
section), you can use term to  multiplex your serial line.   term will
allow you to open  multiple login sessions  over the modem  connection
to a remote machine.   term will also  allow you to redirect X  client
connections to your local X server, through the serial  line, allowing
you to display remote  X applications on your  Linux system.   Another
software package, KA9Q, implements a similar SLIP-like interface.
  Running  a bulletin  board system  (BBS) is  a  favorite hobby  (and
means of income) for many people.  Linux supports a wide  range of BBS
software, most of which  is more powerful  than what is available  for
other operating systems.  With a  phone line, a modem, and  Linux, you
can turn your  system into  a BBS,  providing dial-in  access to  your
system to users worldwide.   BBS software for Linux includes  XBBS and
the UniBoard BBS packages.
  Most BBS  software locks  the user  into a  menu-based system  where
only certain functions and applications are available.  An alternative
to BBS access  is full UNIX  access, which would  allow users to  dial
into your  system and  login as  a regular  user.    While this  would
require a  fair  amount of  maintenance  on  the part  of  the  system
administrator, it can be done,  and providing public UNIX  access from
your Linux  system is  not  difficult to  do.    Along with  a  TCP/IP
network, you can provide electronic  mail and news access to  users on
your system.
  If you do  not have access to a  TCP/IP network or UUCP feed,  Linux
will also allow  you to  communicate with  a number  of BBS  networks,
such as FidoNet, with which you can exchange electronic  news and mail
via the phone line.   More  information on telecommunications and  BBS
software under Linux can be found in Chapter 5.
1.4.   Software Features                                            16
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1.4.7 Interfacing with MS-DOS

Various utilities exist  to interface  with the world  of MS-DOS.  The
most well-known application is the Linux MS-DOS Emulator, which allows
you to run  many MS-DOS applications  directly from  Linux.   Although
Linux and MS-DOS are completely different operating systems, the 80386
protected-mode environment allows certain tasks  to behave as if  they
were running in 8086-emulation mode, as MS-DOS applications do.
  The MS-DOS  emulator is  still under development,  yet many  popular
applications  run  under  it.      Understandably,   however,   MS-DOS
applications which use bizarre or esoteric features of the  system may
never be supported,  because it  is only  an emulator.   For  example,
you wouldn't expect  to be able  to run any  programs which use  80386
protected-mode features, such  as Microsoft  Windows (in 386  enhanced
mode, that is).
  Applications which run successfully under the  Linux MS-DOS Emulator
include 4DOS (a  command interpreter), Foxpro  2.0, Harvard  Graphics,
MathCad, Stacker  3.1,  Turbo Assembler,  Turbo C/C++,  Turbo  Pascal,
Microsoft Windows 3.0 (in real mode),  and WordPerfect 5.1.   Standard
MS-DOS commands and utilities (such as PKZIP, and so on) work with the
emulator as well.
  The MS-DOS Emulator is meant mostly as an ad  hoc solution for those
people who need MS-DOS only for a few applications, but  use Linux for
everything else.   It's not meant to  be a complete implementation  of
MS-DOS. Of course, if the Emulator doesn't satisfy your needs, you can
always run MS-DOS as well as Linux on the same system.  Using the LILO
boot loader, you can  specify at boot  time which operating system  to
start.  Linux can coexist with other operating systems,  such as OS/2,
as well.
  Linux provides a  seamless interface for transferring files  between
Linux and MS-DOS. You  can mount an  MS-DOS partition or floppy  under
Linux, and directly access MS-DOS files as you would any other.
  Currently  under  development   is  a  project  known  as   WINE---a
Microsoft Windows emulator for the X Window System under Linux.   Once
WINE is complete,  users will be able  to run MS-Windows  applications
directly from Linux.  This is similar to the  proprietary WABI Windows
emulator from Sun Microsystems.  At the time of this  writing, WINE is
still in the early stages of development, but the outlook is good.
  In  Chapter 5  we'll  talk  about  the MS-DOS  tools  available  for
Linux.

1.4.8 Other applications

A host  of miscellany  is available  for Linux,  as  one would  expect
from such  a  hodgepodge operating  system.    Linux's  primary  focus
is currently  for  personal  UNIX  computing,   but  this  is  rapidly
changing.    Business  and  scientific  software  is  expanding,   and
commercial software vendors are beginning to contribute to the growing
pool of applications.
  Several  relational databases  are  available for  Linux,  including
1.4.   Software Features                                            17
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Postgres, Ingres, and  Mbase.   These are full-featured,  professional
client/server database applications  similar to  those found on  other
UNIX platforms.  /rdb,  a commercial database system, is  available as
well.
  Scientific computing  applications  include FELT  (a finite  element
analysis tool); gnuplot  (a plotting  and data analysis  application);
Octave (a symbolic mathematics package, similar to MATLAB); xspread (a
spreadsheet calculator);  xfractint, an  X-based port  of the  popular
Fractint fractal  generator;  xlispstat  (a statistics  package),  and
more.  Other applications include Spice (a circuit design and analysis
tool) and Khoros (an image/digital signal processing and visualization
system).
  Of course,  there are many more  such applications which have  been,
and can be,  ported to  run on Linux.   Whatever  your field,  porting
UNIX-based applications  to  Linux should  be  quite  straightforward.
Linux provides a  complete UNIX programming  interface, sufficient  to
serve as the base for any scientific application.
  As with any operating system,  Linux has its share of games.   These
include classic text-based  dungeon games such  as Nethack and  Moria;
MUDs (multi-user dungeons,  which allow  many users to  interact in  a
text-based adventure) such as DikuMUD  and TinyMUD; as well as  a slew
of X games  such as xtetris,  netrek, and Xboard  (the X11 version  of
gnuchess).  The  popular shoot-em-up arcade-style  Doom has also  been
ported to Linux.
  For  audiophiles, Linux  has  support for  various sound  cards  and
related software,  such as  CDplayer (a  program which  can control  a
CD-ROM drive as a conventional  CD player, surprisingly enough),  MIDI
sequencers and editors  (allowing you  to compose  music for  playback
through a synthesizer or other MIDI-controlled instrument),  and sound
editors for digitized sounds.
  Can't find the application  you're looking for?  The  Linux Software
Map, described  in  Appendix  A,  contains  a list  of  many  software
packages which have been written and ported to Linux.  While this list
is far from complete, it contains  a great deal of software.   Another
way to find Linux applications is to look at the INDEX  files found on
Linux FTP sites, if you have  Internet access.  Just by  poking around
you'll find a great deal of software just waiting to be played with.
  If you absolutely can't  find what you need, you can  always attempt
to port the application from another  platform to Linux.   Most freely
distributable UNIX-based  software  will  compile on  Linux  with  few
problems.   Or,  if  all else  fails, you  can  write the  application
yourself.    If it's  a  commercial  application you're  looking  for,
there may  be a  free ``clone''  available.    Or,  you can  encourage
the software company  to consider  releasing a  Linux binary  version.
Several individuals have contacted software companies, asking  them to
port their applications to Linux, and have met with various degrees of
success.
1.5.   About Linux's Copyright                                      18
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1.5 About Linux's Copyright

Linux is covered by what is  known as the GNU General  Public License,
or GPL. The GPL was developed for the GNU project by the Free Software
Foundataion.   It makes a  number of  provisions for the  distribution
and modification of ``free software''.  ``Free'' in this  sense refers
to freedom,  not  just cost.    The  GPL has  always been  subject  to
misinterpretation, and  we hope  that this  summary will  help you  to
understand the extent and goals of the GPL and its effect on Linux.  A
complete copy of the GPL is included in Appendix E.
  Originally,  Linus  Torvalds released  Linux  under a  license  more
restrictive than  the GPL,  which allowed  the software  to be  freely
distributed and modified, but  prevented any money changing hands  for
its distribution and use.  On the other hand, the GPL allows people to
sell and make profit  from free software, but  does not allow them  to
restrict the right for others to distribute the software in any way.
  First, it should be explained that ``free software''  covered by the
GPL is not in the public  domain.  Public domain software  is software
which is  not  copyrighted, and  is  literally  owned by  the  public.
Software covered by  the GPL,  on the  other hand,  is copyrighted  to
the author or  authors.   This  means that the  software is  protected
by standard international copyright laws,  and that the author  of the
software is legally defined.  Just because the software  may be freely
distributed does not mean that it is in the public domain.
  GPL-licensed  software  is  also  not  ``shareware''.     Generally,
``shareware'' software is owned and copyrighted by the author, but the
author requires users to send in money for its use after distribution.
On the other hand, software covered by the GPL may  be distributed and
used free of charge.
  The GPL  also allows people  to take and  modify free software,  and
distribute their own versions of the  software.  However,  any derived
works from GPL  software must  also be  covered by the  GPL. In  other
words, a company could  not take Linux, modify  it, and sell it  under
a restrictive license.   If any software  is derived from Linux,  that
software must be covered by the GPL as well.
  The  GPL allows  free  software  to  be distributed  and  used  free
of charge.    However,  it also  allows a  person  or organization  to
distribute GPL software  for a  fee, and  even to make  a profit  from
its sale and  distribution.   However,  in selling  GPL software,  the
distributor cannot take those rights away from the purchaser; that is,
if you purchase GPL software from some source, you  may distribute the
software for free, or sell it yourself as well.
  This might sound like  a contradiction at first.  Why  sell software
for profit when  the GPL  allows anyone  to obtain it  for free?    As
an example,  let's say that  some company  decided to  bundle a  large
amount of free software on a  CD-ROM and distribute it.   That company
would need to charge  for the overhead  of producing and  distributing
the CD-ROM, and the  company may even decide  to make profit from  the
sales of software.  This is allowed by the GPL.
  Organizations  which   sell  free   software  must  follow   certain
1.6.   The Design and Philosophy of Linux                           19
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restrictions set forth  in the  GPL. First, they  cannot restrict  the
rights of users who  purchase the software.   This  means that if  you
buy a CD-ROM of GPL software, you can copy and  distribute that CD-ROM
free of charge, or  resell it yourself.   Secondly, distributors  must
make it  obvious to  users  that the  software  is indeed  covered  by
the GPL.  Thirdly,  distributors must  provide,  free of  charge,  the
complete source code for  the software being  distributed.  This  will
allow anyone who purchases GPL software to make modifications  of that
software.
  Allowing a company  to distribute and sell  free software is a  very
good thing.    Not everyone  has access  to the  Internet to  download
software, such  as Linux,  for  free.   The  GPL  allows companies  to
sell and distribute  software to  those people  who do  not have  free
(cost-wise) access to the software.   For example,  many organizations
sell Linux  on diskette,  tape, or  CD-ROM via  mail  order, and  make
profit from these sales.   The developers of  Linux may never see  any
of this profit; that is the understanding that is  reached between the
developer and the distributor  when software is  licensed by the  GPL.
In other words, Linus knew that companies may wish to  sell Linux, and
that he may not see a penny of the profits from those sales.
  In the free software world,  the important issue is not money.   The
goal of free software  is always to  develop and distribute  fantastic
software and  to allow  anyone to  obtain and  use it.    In the  next
section, we'll discuss how this applies to the development of Linux.


1.6 The Design and Philosophy of Linux

When new users encounter Linux,  they often have a  few misconceptions
and false expectations  of the system.   Linux  is a unique  operating
system, and it is important to understand its philosophy and design in
order to use it effectively.  Time enough for a soapbox.   Even if you
are an aged UNIX guru, what follows is probably of interest to you.
  In  commercial  UNIX  development  houses,   the  entire  system  is
developed with  a rigorous  policy of  quality assurance,  source  and
revision  control  systems,  documentation,  and   bug  reporting  and
resolution.  Developers are not  allowed to add features or  to change
key sections of code on  a whim:  they  must validate the change as  a
response to a bug report and consequently ``check in'' all  changes to
the source control system,  so that the changes  can be backed out  if
necessary.  Each developer is assigned one or more parts of the system
code, and only  that developer may  alter those  sections of the  code
while it is ``checked out''.
  Internally,   the  quality   assurance   department  runs   rigorous
regression test suites on each new  pass of the operating system,  and
reports any bugs.  It  is the responsibility of the developers  to fix
these bugs as reported.  A complicated system of  statistical analysis
is employed to  ensure that  a certain  percentage of  bugs are  fixed
before the next  release, and  that the  operating system  as a  whole
passes certain release criteria.
  In all, the process  used by commercial UNIX developers  to maintain
1.6.   The Design and Philosophy of Linux                           20
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and support their code is  very complicated, and quite  reasonably so.
The company must  have quantitative  proof that the  next revision  of
the operating system  is ready  to be  shipped;  hence, the  gathering
and analysis of statistics  about the operating system's  performance.
It is  a big  job to  develop a  commercial UNIX  system, often  large
enough to employ hundreds (if not thousands) of  programmers, testers,
documentors,  and  administrative  personel.     Of  course,   no  two
commercial UNIX vendors are alike, but you get the general picture.
  With  Linux, you  can  throw out  the  entire concept  of  organized
development, source  control  systems,  structured bug  reporting,  or
statistical analysis.  Linux is, and more than likely  always will be,
a hacker's operating system.(4)
  Linux is primarily developed as a group effort  by volunteers on the
Internet from all  over the world.   Across  the Internet and  beyond,
anyone with enough know-how has  the opportunity to aid in  developing
and debugging the kernel, porting new software, writing documentation,
or helping new  users.   There is  no single organization  responsible
for developing the  system.   For the most  part, the Linux  community
communicates via  various mailing  lists  and USENET  newsgroups.    A
number of conventions  have sprung up  around the development  effort:
for example,  anyone  wishing  to  have  their code  included  in  the
``official'' kernel should mail  it to Linus  Torvalds, which he  will
test and include in the kernel (as long as it doesn't  break things or
go against the overall design of the system, he will  more than likely
include it).
  The  system itself  is designed  with  a very  open-ended,  feature-
minded approach.    While  recently the  number  of new  features  and
critical changes to the  system have diminished,  the general rule  is
that a new  version of  the kernel  will be released  about every  few
months (sometimes even more frequently than this).  Of course, this is
a very rough figure:   it depends on  a several factors including  the
number of bugs to be fixed, the amount of feedback  from users testing
pre-release versions of the code,  and the amount of sleep  that Linus
has had this week.
  Let it  suffice to  say that not  every single  bug has been  fixed,
and not every problem  ironed out between  releases.   As long as  the
system appears to be free of  critical or oft-manifesting bugs,  it is
considered ``stable'' and new revisions will be released.   The thrust
behind Linux development is not an effort to release perfect, bug-free
code:  it is to  develop a free implementation  of UNIX. Linux is  for
the developers, more than anyone else.
  Anyone who has a  new feature or software application to add  to the
system generally makes it available in an ``alpha''   stage---that is,
a stage for testing by  those brave or unwary  users who want to  bash

----------------------------
 4. What I mean by ``hacker'' is a feverishly dedicated  programmer, a
person who enjoys exploiting computers and generally doing interesting
things with them.   This is  in contrast to  the common denotation  of
``hacker'' as a computer wrongdoer or outlaw.
1.6.   The Design and Philosophy of Linux                           21
_______________________________________________________________________

out problems with the  initial code.   Because the Linux community  is
largely based on the Internet,  alpha software is usually  uploaded to
one or more  of the  various Linux FTP  sites (see  Appendix C) and  a
message posted to one of the Linux USENET newsgroups about  how to get
and test the code.   Users  who download and  test alpha software  can
then mail results, bug fixes, or questions to the author.
  After the initial  problems in the alpha  code have been fixed,  the
code enters  a ``beta''  stage,   in  which it  is usually  considered
stable but  not complete  (that  is,  it works,  but  not all  of  the
features may  be  present).    Otherwise,  it  may go  directly  to  a
``final'' stage  in  which the  software  is considered  complete  and
usable.  For kernel  code, once it  is complete the developer may  ask
Linus to include it in the  standard kernel, or as an  optional add-on
feature to the kernel.
  Keep in  mind that  these are  only conventions---not rules.    Some
people feel so confident with  their software that they don't  need to
release an alpha or test version.  It is always up to the developer to
make these decisions.
  You might be amazed that such a nonstructured  system of volunteers,
programming and debugging a complete  UNIX system, could get  anything
done at all.   As it turns  out, it is one  of the most efficient  and
motivated development efforts ever employed.  The entire  Linux kernel
was written from scratch, without employing any code  from proprietary
sources.  A great deal of work was put forth by volunteers to port all
of the free software  under the sun  to the Linux  system.   Libraries
were written and ported,  filesystems developed, and hardware  drivers
written for many popular devices.
  The Linux software is  generally released as a distribution,   which
is a set  of pre-packaged  software making up  an entire  system.   It
would be quite  difficult for most  users to  build a complete  system
from the ground up,  starting with the  kernel, adding utilities,  and
installing all of  the necessary  software by  hand.   Instead,  there
are a number of software  distributions including everything that  you
need to  install and  run  a complete  system.    Again, there  is  no
standard distribution---there are many, each with their own advantages
and disadvantages.  We'll talk more about the various  available Linux
distributions in Section 2.1.
  Despite the completeness of the Linux software, you  will still need
a bit of  UNIX know-how  to install  and run a  complete system.    No
distribution of Linux is completely  bug-free, so you may  be required
to fix small  problems by  hand after  installation.   Running a  UNIX
system is not an easy task, not even for commercial  versions of UNIX.
If you're  serious about  Linux,  bear in  mind that  it  will take  a
considerable amount of effort and  attention on your part to  keep the
system running and  take care  of things:   this is  true of any  UNIX
system, and Linux is  no exception.   Because of the diversity of  the
Linux community and the many needs which the software is attempting to
meet, not eveything can be taken care of for you all of the time.
1.6.   The Design and Philosophy of Linux                           22
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1.6.1 Hints for UNIX novices

Installing and using your  own Linux system  does not require a  great
deal of background in  UNIX. In fact,  many UNIX novices  successfully
install Linux  on  their systems.     This is  a  worthwhile  learning
experience, but keep in mind that it can be very  frustrating to some.
If you're lucky,  you will  be able  to install and  start using  your
Linux system without any UNIX background.  However, once you are ready
to delve into  the more  complex tasks  of running  Linux---installing
new software, recompiling the kernel, and so forth---having background
knowledge in UNIX is going to be a necessity.
  Fortunately,  by   running  your  own  Linux  system  you   will  be
able to  learn  the essentials  of  UNIX  necessary for  these  tasks.
This book  contains  a  good  deal  of information  to  help  you  get
started---Chapter 3 is a tutorial covering UNIX basics, and  Chapter 4
contains information on Linux system administration.  You may  wish to
read these chapters before you  attempt to install Linux at  all---the
information contained therein will prove  to be invaluable should  you
run into problems.
  Nobody can expect  to go from being a  UNIX novice to a  UNIX system
administrator overnight.  No implementation of UNIX is expected to run
trouble- and maintenance-free.   You  must be  aptly prepared for  the
journey which lies ahead.   Otherwise, if you're new to UNIX,  you may
very well become overly frustrated with the system.

1.6.2 Hints for UNIX gurus

Even  those  people  with  years  of  UNIX  programming   and  systems
administration experience may need assistance before they are  able to
pick up and install Linux.  There are still aspects of the system that
UNIX wizards will need to be familiar with before diving in.   For one
thing, Linux