Tài liệu A Practical Guide to Fedora and Red Hat Enterprise Linux pdf

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Guide to Fedora and Red Hat Enterprise Linux

“Since I’m in an educational environment, I found the content of Sobell’s

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valuable complement to their education The vast amount of

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an experienced computer user who is moving to the Linux platform.”

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IT Director Barbara Davis Center University of Colorado at Denver from a review posted on slashdot.org

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IS Engineer

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Boulder, Colorado

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Praise for Other Books by Mark G Sobell

“This book is a very useful tool for anyone who wants to ‘look under

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BU Linux Project Boston University Office

of Information Technology

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A Practical Guide to Fedora and

Red Hat Enterprise Linux

SIXTH EDITION

¥

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A Practical Guide to Fedora and

Red Hat Enterprise Linux

SIXTH EDITION

Mark G Sobell

Upper Saddle River, NJ • Boston • Indianapolis • San Francisco

New York • Toronto • Montreal • London • Munich • Paris • Madrid

Capetown • Sydney • Tokyo • Singapore • Mexico City

¥

Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks Where

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The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any

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Library of Congress Cataloging-in-Publication Data

Copyright © 2012 Mark G Sobell

All rights reserved Printed in the United States of America This publication is protected by copyright, and permission must

be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any

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from this work, please submit a written request to Pearson Education, Inc., Permissions Department, One Lake Street, Upper

Saddle River, New Jersey 07458, or you may fax your request to (201) 236-3290.

ISBN-13: 978-0-13-275727-0

ISBN-10: 0-13-275727-3

Text printed in the United States on recycled paper at Edwards Brothers in Ann Arbor, Michigan.

First printing, August 2011

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PART II Getting Started with Fedora/RHEL 87

4 Introduction to Fedora and Red Hat Enterprise Linux 89

5 The Linux Utilities 145

6 The Linux Filesystem 185

7 The Shell 225

PART III Digging into Fedora/RHEL 255

8 Linux GUIs: X and GNOME 257

9 The Bourne Again Shell 279

10 Networking and the Internet 359

xiv

11 System Administration: Core Concepts 407

12 Files, Directories, and Filesystems 501

13 Finding, Downloading, and Installing Software 531

14 Printing with CUPS 559

15 Building a Linux Kernel 583

16 Administration Tasks 601

17 Configuring and Monitoring a LAN 645

PART V Using Clients and Setting Up Servers 671

18 OpenSSH: Secure Network Communication 673

19 F TP: Transferring Files Across a Network 701

20 sendmail: Setting Up Mail Servers, Clients, and More 729

21 NIS and LDAP 759

22 NFS: Sharing Directory Hierarchies 791

23 Samba: Linux and Windows File and Printer Sharing 817

24 DNS/BIND: Tracking Domain Names and Addresses 845

25 system-config-firewall and iptables: Setting Up a Firewall 891

26 Apache (httpd): Setting Up a Web Server 917

27 Programming the Bourne Again Shell 969

28 The Perl Scripting Language 1057

Chapter 1: Welcome to Linux 1

The History of UNIX and GNU–Linux 2

The Heritage of Linux: UNIX 2

Fade to 1983 3

Next Scene, 1991 4

The Code Is Free 5

Have Fun! 6

What Is so Good About Linux? 6

Why Linux Is Popular with Hardware Companies and Developers 9

Linux Is Portable 10

The C Programming Language 10

Overview of Linux 11

Linux Has a Kernel Programming Interface 11

Linux Can Support Many Users 12

Linux Can Run Many Tasks 12

Linux Provides a Secure Hierarchical Filesystem 12

The Shell: Command Interpreter and Programming Language 14

A Large Collection of Useful Utilities 15

Interprocess Communication 16

System Administration 16

xvi

Additional Features of Linux 16GUIs: Graphical User Interfaces 16(Inter)Networking Utilities 17Software Development 17Conventions Used in This Book 18Chapter Summary 20

Exercises 20

Chapter 2: Installation Overview 25

The Desktop Live CD and the Install DVD 26More Information 27

Planning the Installation 28Considerations 28Requirements 28Processor Architecture 30Interfaces: Installer and Installed System 31Which Are You Installing: Fedora or Red Hat Enterprise Linux? 32Fedora/RHEL Releases 33

Fedora Standard Versions 33Fedora Spins 33

Installing a Fresh Copy or Upgrading an Existing Fedora/RHEL System? 34Setting Up the Hard Disk 34

Burning the CD/DVD 48Gathering Information About the System 48Chapter Summary 49

Exercises 50Advanced Exercises 50

Chapter 3: Step-by-Step Installation 51

Running a Fedora Live Session 52Booting the System 53Installing Fedora/RHEL 54

xvii

The Anaconda Installer 58

Firstboot: When You Reboot 65

Initializing Databases and Updating the System 67

Installation Tasks 67

Modifying Boot Parameters (Options) 67

Using Disk Druid to Partition the Disk 71

palimpsest: The GNOME Disk Utility 77

Using the Kickstart Configurator 81

Setting Up a Dual-Boot System 82

gnome-control-center/Displays: Configures the Display 85

Chapter Summary 85

Exercises 86

Advanced Exercises 86

Chapter 4: Introduction to Fedora and Red Hat

Enterprise Linux 89

Curbing Your Power (Superuser/root Privileges) 90

A Tour of the Fedora/RHEL Desktop 90

Logging In on the System 91

Configuring Fallback Mode (Fedora) 92

Installing and Using gnome-tweak-tool (Fedora) 94

Introduction to the Desktop 95

Launching Programs from the Desktop 96

Switching Workspaces 98

Setting Personal Preferences 99

Mouse Preferences 101

Working with Windows 102

Using Nautilus to Work with Files 102

Getting the Most Out of the Desktop 112

GNOME Desktop Terminology 112

The ––help Option 131HOWTOs: Finding Out How Things Work 131Getting Help 132

More About Logging In 134The Login Screen 134What to Do if You Cannot Log In 135Logging In Remotely: Terminal Emulators, ssh, and Dial-Up Connections 135Logging In from a Terminal (Emulator) 136

Changing Your Password 137Using Virtual Consoles 138Working from the Command Line 139Correcting Mistakes 139

Repeating/Editing Command Lines 141Chapter Summary 142

Exercises 143Advanced Exercises 144

Chapter 5: The Linux Utilities 145

Special Characters 146Basic Utilities 147ls: Lists the Names of Files 148cat: Displays a Text File 148rm: Deletes a File 148less Is more: Display a Text File One Screen at a Time 149hostname: Displays the System Name 149

Working with Files 149

cp: Copies a File 149mv: Changes the Name of a File 150lpr: Prints a File 151

grep: Searches for a String 152head: Displays the Beginning of a File 152tail: Displays the End of a File 153

sort: Displays a File in Order 154uniq: Removes Duplicate Lines from a File 154diff: Compares Two Files 154

file: Identifies the Contents of a File 156

xix

| (Pipe): Communicates Between Processes 156

Four More Utilities 157

echo: Displays Text 157

date: Displays the Time and Date 158

script: Records a Shell Session 158

unix2dos: Converts Linux and Macintosh Files to Windows Format 159

Compressing and Archiving Files 159

bzip2: Compresses a File 160

bzcat and bunzip2: Decompress a File 161

gzip: Compresses a File 161

tar: Packs and Unpacks Archives 162

Locating Utilities 164

which and whereis: Locate a Utility 164

locate: Searches for a File 166

Displaying User and System Information 166

who: Lists Users on the System 166

finger: Lists Users on the System 167

w: Lists Users on the System 168

Communicating with Other Users 170

write: Sends a Message 170

mesg: Denies or Accepts Messages 170

Ending the Editing Session 179

The compatible Parameter 179

Chapter Summary 179

Exercises 182

Advanced Exercises 183

Chapter 6: The Linux Filesystem 185

The Hierarchical Filesystem 186

Directory Files and Ordinary Files 187

Filenames 188

The Working Directory 190

Your Home Directory 191

Pathnames 191

Absolute Pathnames 192

Relative Pathnames 193

xx

Working with Directories 194mkdir: Creates a Directory 194cd: Changes to Another Working Directory 196rmdir: Deletes a Directory 197

Using Pathnames 198

mv,cp: Move or Copy Files 198mv: Moves a Directory 199Important Standard Directories and Files 199Access Permissions 202

ls –l: Displays Permissions 202chmod: Changes Access Permissions 203Setuid and Setgid Permissions 205Directory Access Permissions 207ACLs: Access Control Lists 208Enabling ACLs 209Working with Access Rules 209Setting Default Rules for a Directory 212Links 213

Hard Links 214Symbolic Links 216rm: Removes a Link 218Chapter Summary 219Exercises 221

Advanced Exercises 222

Chapter 7: The Shell 225

The Command Line 226Syntax 226

Processing the Command Line 229Executing a Command 231Editing the Command Line 231Standard Input and Standard Output 232The Screen as a File 232

The Keyboard and Screen as Standard Input and Standard Output 233Redirection 234

Pipes 239Running a Command in the Background 242Filename Generation/Pathname Expansion 244

The ? Special Character 245

The* Special Character 246

The [ ] Special Characters 247Builtins 249

Chapter Summary 250Utilities and Builtins Introduced in This Chapter 250Exercises 251

xxi

Chapter 8: Linux GUIs: X and GNOME 257

X Window System 258

Using X 260

Desktop Environments/Managers 265

The Nautilus File Browser Window 266

The View Pane 267

Pick a Font Window 273

Pick a Color Window 274

Run Application Window 274

Searching for Files 274

GNOME Terminal Emulator/Shell 276

Commands That Are Symbols 285

Redirecting Standard Error 285

Writing a Simple Shell Script 288

Separating and Grouping Commands 292

Job Control 296

Manipulating the Directory Stack 298

Parameters and Variables 301

Variables That Control History 319

Re-executing and Editing Commands 320

The Readline Library 328

xxii

Aliases 334Single Versus Double Quotation Marks in Aliases 335Examples of Aliases 336

Functions 338Controlling bash: Features and Options 340Command-Line Options 340

Shell Features 341Processing the Command Line 344History Expansion 345Alias Substitution 345Parsing and Scanning the Command Line 345Command-Line Expansion 345

Chapter Summary 354Exercises 356

Advanced Exercises 357

Chapter 10: Networking and the Internet 359

Introduction to Networking 360Types of Networks and How They Work 362Broadcast Networks 362

Point-to-Point Networks 363Switched Networks 363LAN: Local Area Network 364WAN: Wide Area Network 367Internetworking Through Gateways and Routers 367Network Protocols 370

IPv4 372IPv6 373Host Address 376CIDR: Classless Inter-Domain Routing 380Hostnames 380

Communicate Over a Network 381finger: Displays Information About Remote Users 381Mailing List Servers 382

Network Utilities 382Trusted Hosts 382OpenSSH Tools 383telnet: Logs In on a Remote System 383ftp: Transfers Files Over a Network 385ping: Tests a Network Connection 386traceroute: Traces a Route Over the Internet 387host and dig: Query Internet Nameservers 388whois: Looks Up Information About an Internet Site 388

xxiii

Distributed Computing 390

The Client/Server Model 390

DNS: Domain Name Service 391

Chapter 11: System Administration: Core Concepts 407

Running Commands with root Privileges 409

The Special Powers of a Privileged User 410

Gaining root Privileges 410

Usingsu to Gain root Privileges 413

Usingsudo to Gain root Privileges 415

sudoers: Configuring sudo 419

Locking the root Account (Removing the root Password) 425

consolehelper: Allows an Ordinary User to Run a Privileged Command 425

The init Daemon 426

The systemd init Daemon (Fedora) 426

The Upstart init Daemon (RHEL) 436

SysVinit (rc) Scripts: Start and Stop System Services (Fedora/RHEL) 442

xxiv

Rescue Installed System 457Securing a System 458Avoiding a Trojan Horse 458SELinux 459

System Administration Tools 469Textual Administration Utilities 469Graphical Configuration Tools 475Setting Up a Server 477

Standard Rules in Configuration Files 478rpcinfo: Displays Information About rpcbind 480

The xinetd Superserver 481Securing a Server 484DHCP: Configures Network Interfaces 489More Information 490

How DHCP Works 490DHCP Client 491DHCP Server 491

nsswitch.conf: Which Service to Look at First 494Information 494

Methods 495Search Order 495Action Items 495

compat Method: ± in passwd, group, and shadow Files 496Getting Help 497

Chapter Summary 497Exercises 498

Advanced Exercises 499

Chapter 12: Files, Directories, and Filesystems 501

Important Files and Directories 502File Types 514

Ordinary Files, Directories, Links, and Inodes 515Device Special Files 515

Filesystems 519mount: Mounts a Filesystem 520umount: Unmounts a Filesystem 523

fstab: Keeps Track of Filesystems 524fsck: Checks Filesystem Integrity 525tune2fs: Changes Filesystem Parameters 526Chapter Summary 528

Exercises 528

JumpStart: Installing and Removing Packages Using yum 534

Finding the Package That Holds an Application or File You Need 537

yum: Keeps the System Up-to-Date 538

Updating Packages 539

yum Commands 540

yum Groups 540

Downloading RPM Package Files with yumdownloader 541

yum.conf: Configures yum 542

yum Repositories 543

BitTorrent 545

RPM: The RPM Package Manager 547

Querying Packages and Files 548

Installing, Upgrading, and Removing Packages 550

Installing a Linux Kernel Binary 551

Installing Non-rpm Software 551

The /opt and /usr/local Directories 551

GNU Configure and Build System 552

Keeping Software Up-to-Date 553

Bugs 553

Errata 554

Red Hat Network (RHEL) 554

wget: Downloads Files Noninteractively 555

Fedora/RHEL Configures a Local Printer Automatically 562

JumpStart I: Configuring a Printer Using system-config-printer 562

Configuration Selections 563

JumpStart II: Setting Up a Local or Remote Printer 565

Working with the CUPS Web Interface 568

Configuring Printers 570

Modifying a Printer 570

The CUPS Web Interface 571

CUPS on the Command Line 572

Sharing CUPS Printers 576

xxvi

Traditional UNIX Printing 577Print from Windows 579Print Using CUPS 579Print Using Samba 580Printing to Windows 581Chapter Summary 581Exercises 582

Advanced Exercises 582

Chapter 15: Building a Linux Kernel 583

Downloading, Installing, and Prepping the Kernel Source Code 585Prerequisites 585

More Information 585Downloading the Source Code 585Installing the Source Code 587Prepping the Source Code 587Configuring and Compiling the Linux Kernel 588Labeling the Kernel 588

.config: Configures the Kernel 589

Customizing a Kernel 590Cleaning the Source Tree 592Copying the Configuration File 593Compiling a Kernel Image File and Loadable Modules 593Using Loadable Kernel Modules 593

Installing the Kernel, Modules, and Associated Files 594GRUB: The Linux Boot Loader 595

Configuring GRUB 596grub-install: Installs the MBR and GRUB Files 597dmesg: Displays Kernel Messages 597

Chapter Summary 598Exercises 598

Advanced Exercises 599

Chapter 16: Administration Tasks 601

Configuring User and Group Accounts 602system-config-users: Manages User Accounts 602Managing User Accounts from the Command Line 604Backing Up Files 605

Choosing a Backup Medium 606Backup Utilities 607

Performing a Simple Backup 610Scheduling Tasks 611

xxvii

System Reports 615

vmstat: Reports Virtual Memory Statistics 615

top: Lists Processes Using the Most Resources 616

Maintaining the System 617

parted: Reports on and Partitions a Hard Disk 617

logrotate: Manages Log Files 621

rsyslogd: Logs System Messages 623

Keeping Users Informed 625

The my.cnf Configuration File 638

Working with MySQL 638

Chapter Summary 643

Exercises 643

Advanced Exercises 644

Setting Up the Hardware 646

Connecting the Computers 646

Routers 647

NIC: Network Interface Card 647

Tools 648

Configuring the Systems 650

NetworkManager: Configures Network Connections 651

The NetworkManager Applet Right-Click Menu 651

Basic Cacti Administration 663

Setting Up a Remote Data Source 664

More Information 668

Chapter Summary 668

Exercises 669

Advanced Exercises 669

More Information 677Running the ssh,scp, and sftp OpenSSH Clients 677Prerequisites 677

JumpStart: Using ssh and scp to Connect to an OpenSSH Server 677Configuring OpenSSH Clients 678

ssh: Logs in or Executes Commands on a Remote System 681scp: Copies Files to and from a Remote System 683

sftp: A Secure FTP Client 685

~/.ssh/config and /etc/ssh/ssh_config Configuration Files 686

Setting Up an OpenSSH Server (sshd) 688Prerequisites 688

Notes 688JumpStart: Starting an OpenSSH Server 688Authorized Keys: Automatic Login 689ssh-agent: Holds Your Private Keys 691Command-Line Options 692

/etc/ssh/sshd_config Configuration File 692Troubleshooting 695

Tunneling/Port Forwarding 696Forwarding X11 696Port Forwarding 697Chapter Summary 698Exercises 699

Advanced Exercises 699

Chapter 19 F TP: Transferring Files Across a

Introduction to FTP 702Security 702

FTP Connections 703FTP Clients 703

JumpStart I: Configuring sendmail on a Client 733

JumpStart II: Configuring sendmail on a Server 734

Working with sendmail Messages 735

Mail Logs 736

Aliases and Forwarding 736

Related Programs 738

Configuring sendmail 739

The sendmail.mc and sendmail.cf Files 739

Other Files in /etc/mail 741

Chapter Summary 756Exercises 757

Advanced Exercises 757

Chapter 21: NIS and LDAP 759

Introduction to NIS 760How NIS Works 760More Information 763Running an NIS Client 763Prerequisites 763Notes 764Configuring an NIS Client 764Troubleshooting the Client 766yppasswd: Changes NIS Passwords 767Setting Up an NIS Server 769

Prerequisites 769Notes 770Configuring the Server 770Troubleshooting the Server 775

yppasswdd: The NIS Password Update Daemon 775

LDAP 776More Information 778Setting Up an LDAP Server 779Prerequisites 779

Note 779Step-by-Step Setup 779Tools for Working with LDAP 784Evolution Mail 785

Chapter Summary 788Exercises 789

Advanced Exercises 789

Chapter 22: NFS: Sharing Directory Hierarchies 791

Introduction to NFS 793More Information 795

xxxi

Running an NFS Client 795

Prerequisites 796

JumpStart I: Mounting a Remote Directory Hierarchy 796

mount: Mounts a Directory Hierarchy 797

JumpStart II: Configuring an NFS Server Using system-config-nfs (Fedora) 802

Manually Exporting a Directory Hierarchy 804

Where the System Keeps NFS Mount Information 808

exportfs: Maintains the List of Exported Directory Hierarchies 809

Samba Users, User Maps, and Passwords 820

smbpasswd and pdbedit: Work with Samba Users and Passwords 821

Running Samba Clients 822

Prerequisites 822

Working with Shares from Linux 823

Working with Shares from Windows 825

Setting Up a Samba Server 826

Prerequisites 826

JumpStart: Configuring a Samba Server Using system-config-samba

(Fedora) 827

swat: Configures a Samba Server 830

smb.conf: Manually Configuring a Samba Server 834

Troubleshooting 840

Chapter Summary 843

Exercises 844

Advanced Exercises 844

Queries 850Servers 850Resource Records 851DNS Queries and Responses 855Reverse Name Resolution 856How DNS Works 857

More Information 858Setting Up a DNS Server 858Prerequisites 858Notes 859JumpStart I: Setting Up a DNS Cache 860JumpStart II: Setting Up a Domain Using system-config-bind (Fedora) 861Configuring a DNS Server 866

named.conf: The named Configuration File 866Zone Files 868

Setting Up a DNS Cache 869DNS Glue Records 874TSIGs: Transaction Signatures 875Running BIND in a chroot Jail 877Troubleshooting 878

Setting Up Different Types of DNS Servers 879

Chapter 25: system-config-firewall and iptables : Setting Up a Firewall 891

JumpStart: Building a Firewall Using system-config-firewall 893Introduction to iptables 895

More Information 898Prerequisites 898Notes 899Anatomy of an iptables Command 900

Copying Rules to and from the Kernel 908

system-config-firewall: Generates a Set of Rules 909

Sharing an Internet Connection Using NAT 910

Connecting Several Clients to a Single Internet Connection 911

Connecting Several Servers to a Single Internet Connection 913

Directives I: Directives You Might Want to Modify as You Get Started 925

Contexts and Containers 930

Directives II: Advanced Directives 935

The Fedora/RHEL httpd.conf File 947

Section 1: Global Environment 948

Section 2: Main Server Configuration 949

Section 3: Virtual Hosts 950

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webalizer: Analyzes Web Traffic 963MRTG: Monitors Traffic Loads 964Error Codes 964

Chapter Summary 965Exercises 965

Advanced Exercises 966

type: Displays Information About a Command 1019read: Accepts User Input 1019

exec: Executes a Command or Redirects File Descriptors 1022trap: Catches a Signal 1025

kill: Aborts a Process 1028getopts: Parses Options 1028

A Partial List of Builtins 1031Expressions 1032

Arithmetic Evaluation 1032Logical Evaluation (Conditional Expressions) 1033

A Recursive Shell Script 1041

The quiz Shell Script 1044

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Appendix A: Regular Expressions 1105

Characters 1106Delimiters 1106Simple Strings 1106Special Characters 1106Periods 1107Brackets 1107Asterisks 1108Carets and Dollar Signs 1108Quoting Special Characters 1109Rules 1109

Longest Match Possible 1109Empty Regular Expressions 1110Bracketing Expressions 1110

The Replacement String 1110Ampersand 1111

Quoted Digit 1111Extended Regular Expressions 1111Appendix Summary 1113

Appendix B: Help 1115

Solving a Problem 1116Finding Linux-Related Information 1117Documentation 1117

Useful Linux Sites 1118Linux Newsgroups 1119Mailing Lists 1119Words 1120Software 1120Office Suites and Word Processors 1122Specifying a Terminal 1122

Appendix C: Security 1125

Encryption 1126Public Key (Asymmetric) Encryption 1127Symmetric Key Encryption 1129

Encryption Implementation 1130GnuPG/PGP 1130

File Security 1131

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Email Security 1131

MTAs (Mail Transfer Agents) 1132

MUAs (Mail User Agents) 1132

Network Security 1132

Network Security Solutions 1133

Network Security Guidelines 1133

Host Security 1135

Login Security 1136

Remote Access Security 1137

Viruses and Worms 1138

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JumpStarts

JumpStarts get you off to a quick start when you need to use a client or set up a server

Once you have the client or server up and running, you can refine its configuration

using the information presented in the sections following each JumpStart

yum (Software Packages)

Installing and Removing Packages Using yum 534

CUPS (Printing)

Configuring a Printer Using system-config-printer 562

Setting Up a Local or Remote Printer 565

MySQL (Database)

Setting Up MySQL 636

OpenSSH (Secure Communication)

Usingssh and scp to Connect to an OpenSSH Server 677

Starting an OpenSSH Server 688

FTP (Download and Upload Files)

Downloading Files Using ftp 704

Starting a vsftpd FTP Server 713