Linux Bible 9th Edition. Wiley

Christopher Negus

Ninth Ed

Published by
John Wiley & Sons, Inc.
10475 Crosspoint Boulevard
Indianapolis, IN 46256
www.wiley.com

Linux Bible 9th Edition

About the Author
Chris Negus is a Red Hat Certifi ed Instructor (RHCI), Red Hat Certifi ed Examiner (RHCX),
Red Hat Certifi ed Architect (RHCA), and Principal Technical Writer for Red Hat Inc. In more
than six years with Red Hat, Chris has taught hundreds of IT professionals aspiring to
become Red Hat Certifi ed Engineers (RHCE).

In his current position at Red Hat, Chris produces articles for the Red Hat Customer Portal.
The projects he works on include Red Hat Enterprise Linux 7, Red Hat Enterprise OpenStack
Platform, Red Hat Enterprise Virtualization and Linux containers in Docker format.
Besides his RHCA certifi cation, Chris is a Red Hat Certifi ed Virtualization Administrator
(RHCVA) and Red Hat Certifi ed Datacenter Specialist (RHCDS). He also has certifi cates of
expertise in Deployment and Systems Management, Clustering and Storage Management,
Cloud Storage, and Server Hardening.

Before joining Red Hat, Chris wrote or co-wrote dozens of books on Linux and UNIX, including
Red Hat Linux Bible (all editions), CentOS Bible, Fedora Bible, Linux Troubleshooting Bible,
Linux Toys and Linux Toys II. Chris also co-authored several books for the Linux Toolbox
series for power users: Fedora Linux Toolbox, SUSE Linux Toolbox, Ubuntu Linux Toolbox, Mac
OS X Toolbox, and BSD UNIX Toolbox.

For eight years Chris worked with the organization at AT&T that developed UNIX before
moving to Utah to help contribute to Novell’s UnixWare project in the early 1990s. When
not writing about Linux, Chris enjoys playing soccer and just hanging out with his wife,
Sheree, and son, Seth.


About the Technical Editor
Richard Blum, LPIC-1, has worked in the IT industry for more than 20 years as both a
systems and network administrator and has published numerous Linux and open source
books. He has administered UNIX, Linux, Novell, and Microsoft servers, as well as helped
design and maintain a 3,500-user network utilizing Cisco switches and routers. He has used
Linux servers and shell scripts to perform automated network monitoring and has written
shell scripts in most of the common Linux shell environments. Rich is an online instructor
for an Introduction to Linux course that is used by colleges and universities across the
United States. When he isn’t being a computer nerd, Rich plays electric bass in a couple of
different church worship bands, and enjoys spending time with his wife, Barbara, and two
daughters, Katie Jane and Jessica.


Acknowledgments
Since I was hired by Red Hat Inc. more than six years ago, I have been exposed to
many of the best Linux developers, testers, support professionals and instructors in
the world. Since I can’t thank everyone individually, I instead salute the culture of
cooperation and excellence that serves to improve my own Linux skills every day.

I don’t speak well of Red Hat because I work there; I work at Red Hat because it lives up
to the ideals of open source software in ways that match my own beliefs. There are a few
people at Red Hat I would like to acknowledge particularly. Discussions with Victor Costea,
Andrew Blum, and other Red Hat instructors have helped me adapt my ways of thinking
about how people learn Linux. I’m able to work across a wide range of technologies because
of the great support I get from my supervisor, Adam Strong, and my senior manager, Sam
Knuth, who both point me toward cool projects but never hold me back.

In this edition, particular help came from Ryan Sawhill Aroha, who helped me simplify my
writing on encryption technology. For the new content I wrote in this book on Linux cloud
technologies, I’d like to thank members of OpenStack, Docker, and RHEV teams, who help
me learn cutting-edge cloud technology every day.

As for the people at Wiley, thanks for letting me continue to develop and improve this book
over the years. Marty Minner has helped keep me on task through a demanding schedule.
Mary Beth Wakefi eld and Ken Brown have been there to remind me at the times I forgot it
was a demanding schedule. Thanks to Richard Blum for his reliably thorough job of tech
editing. Thanks to Margot Maley Hutchison from Waterside Productions for contracting the
book for me with Wiley and always looking out for my best interests.

Finally, thanks to my wife, Sheree, for sharing her life with me and doing such a great job
raising Seth and Caleb.


Introduction

You can’t learn Linux without using it.

I’ve come to that conclusion over more than a decade of teaching people to learn Linux. You

can’t just read a book; you can’t just listen to a lecture. You need someone to guide you and

you need to jump in and do it.

In 1999, Wiley published my Red Hat Linux Bible. The book’s huge success gave me the opportunity to become a full-time, independent Linux author. For about a decade, I wrote dozens of Linux books and explored the best ways to explain Linux from the quiet of my small home office. In 2008, I hit the road. I was hired by Red Hat, Inc., as a full-time instructor, teaching Linux to professional system administrators seeking Red Hat Certifi ed Engineer (RHCE) certifi cation. In my three years as a Linux instructor, I honed my teaching skills in front of live people whose Linux experience ranged from none to experienced professional.

In the previous edition, I turned my teaching experience into text to take a reader from someone who has never used Linux to someone with the skills to become a Linux professional. In this edition, I set out to extend those skills into the cloud. The focus of this ninth edition of the Linux

Bible can be summed up in these ways:

■ Beginner to certified professional: As long as you have used a computer, mouse, and

keyboard, you can start with this book. I tell you how to get Linux, begin using it, step

through critical topics, and ultimately excel at administering and securing it.

■ System administrator–focused: When you are fi nished with this book, you will know how

to use Linux and how to modify and maintain it. All the topics needed to become a Red Hat

Certifi ed Engineer are covered in this book. That said, many software developers have also

used this book to understand how to work on a Linux system as a development platform or

target for their applications.

■ Emphasis on command-line tools: Although point-and-click interfaces for managing

Linux have improved greatly in recent years, many advanced features can only be utilized

by typing commands and editing confi guration fi les manually. I teach you how to become

profi cient with the Linux command-line shell and occasionally compare shell features with

graphical tools for accomplishing the same tasks.

■ Aimed at fewer Linux distributions: In previous editions, I described about 18 different

Linux distributions. With only a few notable exceptions, most popular Linux distributions

are either Red Hat–based (Red Hat Enterprise Linux, Fedora, CentOS, and so on) or Debianbased

(Ubuntu, Linux Mint, KNOPPIX, and so on). Although this book most thoroughly covers

Red Hat distributions, I have increased coverage of Ubuntu throughout in this edition

(because that’s what many of the biggest Linux fans start with).

■ Many, many demos and exercises: Instead of just telling you what Linux does, I

actually show you what it does. Then, to make sure you got it, you have the opportunity

to try exercises yourself. Every procedure and exercise has been tested to

work in Fedora or Red Hat Enterprise Linux. Most work in Ubuntu as well.

■ Lead into cloud technologies: Linux is at the heart of most technological advances

in cloud computing today. That means you need a solid understanding of Linux

to work effectively in tomorrow’s data centers. Learn Linux basics in the front of

this book. Then in the last few chapters, I demonstrate how you can try out Linux

systems as hypervisors, cloud controllers, and virtual machines, as well as manage

virtual networks and networked storage.

How This Book Is Organized

The book is organized to enable you to start off at the very beginning with Linux and grow

to become a professional Linux system administrator and power user.

Part I, “Getting Started,” includes two chapters designed to help you understand what

Linux is and get you started with a Linux desktop:

■ Chapter 1, “Starting with Linux,” covers topics such as what the Linux operating

system is, where it comes from, and how to get started using it.

■ Chapter 2, “Creating the Perfect Linux Desktop,” provides information on how you

can create a desktop system and use some of the most popular desktop features.

Part II, “Becoming a Linux Power User,” provides in-depth details on how to use the Linux

shell, work with fi lesystems, manipulate text fi les, 

manage processes, and use shell scripts:

■ Chapter 3, “Using the Shell,” includes information on how to access a shell, run

commands, recall commands (using history), and do tab completion. The chapter

also describes how to use variables, aliases, and man pages (traditional Linux command reference pages).

■ Chapter 4, “Moving around the Filesystem,” includes commands for listing, creating,

copying, and moving fi les and directories. More advanced topics in this chapter

include fi lesystem security, such as fi le ownership, permissions, and access control lists.

■ Chapter 5, “Working with Text Files,” includes everything from basic text editors to

tools for fi nding fi les and searching for text within fi les.

■ Chapter 6, “Managing Running Processes,” describes how to see what processes are

running on your system and change those processes. Ways of changing processes

include killing, pausing, and sending other types of signals.

■ Chapter 7, “Writing Simple Shell Scripts,” includes shell commands and functions

you can gather together into a fi le to run as a command itself.

In Part III, “Becoming a Linux System Administrator,” 

you learn how to administer Linux systems:

■ Chapter 8, “Learning System Administration,” provides information on basic

graphical tools, commands, and confi guration fi les for administering Linux systems.

■ Chapter 9, “Installing Linux,” covers common installation tasks, such as disk

partitioning and initial software package selection, as well as more advanced

installation tools, such as installing from kickstart fi les.

■ Chapter 10, “Getting and Managing Software,” provides an understanding

of how software packages work and how to get and manage software packages.

■ Chapter 11, “Managing User Accounts,” discusses tools for adding and deleting

users and groups, as well as how to centralize user account management.

■ Chapter 12, “Managing Disks and Filesystems,” provides information on adding

partitions, creating fi lesystems, and mounting fi lesystems, as well as working with

logical volume management.

In Part IV, “Becoming a Linux Server Administrator,” you learn to create powerful network

servers and the tools needed to manage them:

■ Chapter 13, “Understanding Server Administration,” covers remote logging,

monitoring tools, and the Linux boot process.

■ Chapter 14, “Administering Networking,” discusses how to confi gure networking.

■ Chapter 15, “Starting and Stopping Services,” provides information on starting and

stopping services.

■ Chapter 16, “Confi guring a Print Server,” describes how to confi gure printers to use

locally on your Linux system or over the network from other computers.

■ Chapter 17, “Confi guring a Web Server,” describes how to confi gure an Apache Web server.

■ Chapter 18, “Confi guring an FTP Server,” covers procedures for setting up a vsftpd FTP

server that can be used to enable others to download fi les from your Linux system over the network.

■ Chapter 19, “Confi guring a Windows File Sharing (Samba) Server,” covers Windows file server confi guration with Samba.

■ Chapter 20, “Confi guring an NFS File Server,” describes how to use

Network File System features to share folders of fi les among systems over a network.

■ Chapter 21, “Troubleshooting Linux,” covers popular tools for troubleshooting your Linux system.

In Part V, “Learning Linux Security Techniques,” 

you learn how to secure your Linux systems and services:

■ Chapter 22, “Understanding Basic Linux Security,” covers basic security concepts

and techniques.

■ Chapter 23, “Understanding Advanced Linux Security,” provides information on

using Pluggable Authentication Modules (PAM) and cryptology tools to tighten system security and authentication.

■ Chapter 24, “Enhancing Linux Security with SELinux,” shows you how to enable

Security Enhanced Linux (SELinux) to secure system services.

■ Chapter 25, “Securing Linux on the Network,” covers network security features,

such as firewalld and iptables fi rewalls, to secure system services.

Part VI, “Extending Linux into the Cloud,” 

takes you into cutting-edge cloud technologies:

■ Chapter 26, “Using Linux for Cloud Computing,” introduces concepts of cloud computing

in Linux by describing how to set up hypervisors, build virtual machines, and share resources across networks.

■ Chapter 27, “Deploying Linux to the Cloud,” describes how to deploy Linux images

to different cloud environments, including OpenStack, Amazon EC2, or a local Linux

system confi gured for virtualization.

Part VII contains two appendixes to help you get the most from your exploration of Linux.

Appendix A, “Media,” provides guidance on downloading Linux distributions. Appendix B,

“Exercise Answers,” provides sample solutions to the exercises included in chapters 2 through 26.

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Table of Contents

Acknowledgments . . . . . . . . . . . . . . . . . . xi

Introduction . . . . . . . .. . . . . . . . xxxiii

Part I: Getting Started

Chapter 1: Starting with Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Understanding What Linux Is ................................................................................ 4

Understanding How Linux Differs from Other Operating Systems .............................. 6

Exploring Linux History ........................................................................................ 6

Free-fl owing UNIX culture at Bell Labs ........................................................... 7

Commercialized UNIX ................................................................................... 9

Berkeley Software Distribution arrives .................................................. 9

UNIX Laboratory and commercialization .............................................. 10

GNU transitions UNIX to freedom .................................................................11

BSD loses some steam ................................................................................. 13

Linus builds the missing piece .................................................................... 13

OSI open source defi nition .......................................................................... 14

Understanding How Linux Distributions Emerged .................................................. 16

Choosing a Red Hat distribution .................................................................. 17

Using Red Hat Enterprise Linux .......................................................... 17

Using Fedora...................................................................................... 18

Choosing Ubuntu or another Debian distribution .......................................... 19

Finding Professional Opportunities with Linux Today ............................................ 20

Understanding how companies make money with Linux ................................ 21

Becoming Red Hat certifi ed ......................................................................... 22

RHCSA topics ..................................................................................... 23

RHCE topics ....................................................................................... 24

Summary ............................................................................................................ 26

Chapter 2: Creating the Perfect Linux Desktop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Understanding Linux Desktop Technology ............................................................ 30

Starting with the Fedora GNOME Desktop

Live image ..................................................................................................... 32

Using the GNOME 3 Desktop ................................................................................. 33

After the computer boots up ....................................................................... 33

Navigating with the mouse ................................................................. 34

Navigating with the keyboard ............................................................. 38

Setting up the GNOME 3 desktop ...................................................................41

Extending the GNOME 3 desktop .................................................................. 42

Using GNOME shell extensions ............................................................. 42

Using the GNOME Tweak Tool ............................................................... 44

Starting with desktop applications .............................................................. 45

Managing fi les and folders with Nautilus ............................................. 45

Installing and managing additional software ....................................... 46

Playing music with Rhythmbox .......................................................... 48

Stopping the GNOME 3 desktop .................................................................... 49

Using the GNOME 2 Desktop ................................................................................. 49

Using the Metacity window manager ............................................................ 50

Changing GNOME’s appearance ..................................................................... 52

Using the GNOME panels .............................................................................. 53

Using the Applications and System menus ........................................... 54

Adding an applet ............................................................................... 54

Adding another panel ........................................................................ 55

Adding an application launcher .......................................................... 55

Adding a drawer ................................................................................ 56

Changing panel properties .................................................................. 57

Adding 3D effects with AIGLX ..................................................................... 58

Summary ............................................................................................................ 60

Exercises .............................................................................................................61

Part II: Becoming a Linux Power User

Chapter 3: Using the Shell . . . . . . . . . . . . . . . . . . . . . . . . . . 65

About Shells and Terminal Windows ..................................................................... 66

Using the shell prompt ................................................................................ 67

Using a terminal window ............................................................................ 68

Using virtual consoles ................................................................................ 69

Choosing Your Shell ............................................................................................. 69

Running Commands ............................................................................................ 70

Understanding command syntax .................................................................. 71

Locating commands .....................................................................................74

Recalling Commands Using Command History.........................................................76

Command-line editing ................................................................................ 77

Command-line completion ........................................................................... 79

Command-line recall ................................................................................... 80

Connecting and Expanding Commands .................................................................. 82

Piping between commands .......................................................................... 82

Sequential commands ................................................................................. 83

Background commands ............................................................................... 83

Expanding commands ................................................................................. 84

Expanding arithmetic expressions ............................................................... 84

Expanding variables ................................................................................... 85

Using Shell Variables ........................................................................................... 85

Creating and using aliases ........................................................................... 87

Exiting the shell ......................................................................................... 88

Creating Your Shell Environment .......................................................................... 88

Confi guring your shell ................................................................................ 88

Setting your prompt ................................................................................... 89

Adding environment variables ..................................................................... 91

Getting Information about Commands .................................................................. 92

Summary ............................................................................................................ 94

Exercises ............................................................................................................ 95

Chapter 4: Moving around the Filesystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Using Basic Filesystem Commands .......................................................................100

Using Metacharacters and Operators ....................................................................102

Using fi le-matching metacharacters ............................................................102

Using fi le-redirection metacharacters .........................................................103

Using brace expansion characters ...............................................................105

Listing Files and Directories ...............................................................................105

Understanding File Permissions and Ownership ....................................................109

Changing permissions with chmod (numbers) .............................................. 111

Changing permissions with chmod (letters) ................................................. 111

Setting default fi le permission with umask .................................................112

Changing fi le ownership.............................................................................113

Moving, Copying, and Removing Files ..................................................................114

Summary ...........................................................................................................115

Exercises ...........................................................................................................115

Chapter 5: Working with Text Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Editing Files with vim and vi ..............................................................................117

Starting with vi ........................................................................................119

Adding text ......................................................................................119

Moving around in the text .................................................................120

Deleting, copying, and changing text .................................................121

Pasting (putting) text .......................................................................122

Repeating commands ........................................................................122

Exiting vi .........................................................................................122

Skipping around in the fi le ........................................................................123

Searching for text .....................................................................................124

Using ex mode ...........................................................................................124

Learning more about vi and vim .................................................................124

Finding Files......................................................................................................125

Using locate to fi nd fi les by name ...............................................................125

Searching for fi les with fi nd .......................................................................127

Finding fi les by name ........................................................................127

Finding fi les by size ..........................................................................128

Finding fi les by user..........................................................................128

Finding fi les by permission ................................................................129

Finding fi les by date and time ...........................................................130

Using ‘not’ and ‘or’ when fi nding fi les .................................................131

Finding fi les and executing commands ...............................................131

Searching in fi les with grep........................................................................132

Summary ...........................................................................................................134

Exercises ...........................................................................................................134

Chapter 6: Managing Running Processes . . . . . . . . . . . . . . . . . . . . . 137

Understanding Processes ....................................................................................137

Listing Processes ...............................................................................................138

Listing processes with ps ...........................................................................138

Listing and changing processes with top .....................................................140

Listing processes with System Monitor ........................................................142

Managing Background and Foreground Processes ..................................................144

Starting background processes ...................................................................144

Using foreground and background commands ..............................................145

Killing and Renicing Processes ............................................................................146

Killing processes with kill and killall ..........................................................146

Using kill to signal processes by PID ...................................................147

Using killall to signal processes by name ............................................148

Setting processor priority with nice and renice ...........................................148

Limiting Processes with cgroups..........................................................................149

Summary ...........................................................................................................151

Exercises ...........................................................................................................151

Chapter 7: Writing Simple Shell Scripts . . . . . . . . .  . . . . . . . . . . . . . . . . . . . 153

Understanding Shell Scripts ................................................................................153

Executing and debugging shell scripts ........................................................154

Understanding shell variables ....................................................................154

Special shell positional parameters .....................................................156

Reading in parameters ......................................................................157

Parameter expansion in bash .............................................................157

Performing arithmetic in shell scripts .........................................................158

Using programming constructs in shell scripts.............................................159

The “if…then” statements .................................................................159

The case command ............................................................................162

The “for…do” loop ............................................................................163

The “while…do” and “until…do” loops ...............................................164

Trying some useful text manipulation programs ..........................................164

The general regular expression parser .................................................165

Remove sections of lines of text (cut) .................................................165

Translate or delete characters (tr) ......................................................165

The stream editor (sed) .....................................................................166

Using simple shell scripts ...........................................................................167

Telephone list ...................................................................................167

Backup script ...................................................................................168

Summary ...........................................................................................................168

Exercises ...........................................................................................................169

Part III: Becoming a Linux System Administrator

Chapter 8: Learning System Administration . . . . . . . . . . . . . . . . . . . . . . . 173

Understanding System Administration ................................................................173

Using Graphical Administration Tools ..................................................................175

Using system-confi g-* tools ........................................................................175

Using browser-based admin tools ................................................................177

Using the root user account ................................................................................177

Becoming root from the shell (su command) ................................................178

Allowing administrative access via the GUI .................................................180

Gaining administrative access with sudo .....................................................180

Exploring Administrative Commands, Confi guration Files, and Log Files ................182

Administrative commands .........................................................................182

Administrative confi guration fi les ..............................................................183

Administrative log fi les and systemd journal ...............................................188

Using journalctl to view the systemd journal ......................................188

Managing log messages with rsyslogd .................................................189

Using Other Administrative Accounts ..................................................................189

Checking and Confi guring Hardware ....................................................................190

Checking your hardware ............................................................................191

Managing removable hardware ...................................................................194

Working with loadable modules ..................................................................197

Listing loaded modules ......................................................................197

Loading modules ...............................................................................198

Removing modules ............................................................................198

Summary ...........................................................................................................199

Exercises ...........................................................................................................199

Chapter 9: Installing Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

Choosing a Computer ..........................................................................................202

Installing Fedora from Live media .......................................................................203

Installing Red Hat Enterprise Linux from

Installation Media .........................................................................................208

Understanding Cloud-Based Installations .............................................................211

Installing Linux in the Enterprise .......................................................................211

Exploring Common Installation Topics .................................................................213

Upgrading or installing from scratch ...........................................................213

Dual booting .............................................................................................214

Installing Linux to run virtually ................................................................216

Using installation boot options ..................................................................216

Boot options for disabling features ....................................................217

Boot options for video problems .........................................................217

Boot options for special installation types ..........................................218

Boot options for kickstarts and remote repositories .............................218

Miscellaneous boot options ................................................................219

Using specialized storage ...........................................................................219

Partitioning hard drives ............................................................................220

Understanding different partition types .............................................221

Reasons for different partitioning schemes .........................................222

Tips for creating partitions ................................................................222

Using the GRUB boot loader ........................................................................224

Using GRUB Legacy (version 1) ...........................................................225

Using GRUB 2 ...................................................................................229

Summary ...........................................................................................................231

Exercises ...........................................................................................................231

Chapter 10: Getting and Managing Software . . .. . . . . . . . . . . . . . . . . . 233

Managing Software on the Desktop .....................................................................233

Going Beyond the Software Window ....................................................................235

Understanding Linux RPM and DEB Software Packaging ........................................236

Understanding DEB packaging ....................................................................237

Understanding RPM packaging ...................................................................238

What is in an RPM? ...........................................................................238

Where do RPMs come from? ................................................................239

Installing RPMs ................................................................................239

Managing RPM Packages with YUM ......................................................................240

Understanding how yum works ...................................................................241

1. Checking /etc/yum.conf ................................................................242

2. Checking /etc/sysconfi g/rhn/up2date (RHEL only) ..........................242

3. Checking /etc/yum.repos.d/*.repo fi les ...........................................243

4. Downloading RPM packages and metadata from a YUM repository .....243

5. RPM packages installed to Linux fi le system ....................................244

6. Store YUM repository metadata to local RPM database ......................244

Using YUM with third-party software repositories........................................244

Managing software with the YUM command ................................................245

Searching for packages ......................................................................246

Installing and removing packages ......................................................247

Updating packages ............................................................................249

Updating groups of packages .............................................................250

Maintaining your RPM package database and cache .............................251

Downloading RPMs from a yum repository ..........................................252

Installing, Querying, and Verifying Software

with the rpm Command ..................................................................................252

Installing and removing packages with rpm ................................................253

Querying rpm information .........................................................................254

Verifying RPM packages .............................................................................255

Managing Software in the Enterprise ...................................................................256

Summary ...........................................................................................................257

Exercises ...........................................................................................................258

Chapter 11: Managing User Accounts . . . . . .. . . . . . . . . . . . . . . . . . . . 259

Creating User Accounts .......................................................................................259

Adding users with useradd .........................................................................262

Setting user defaults .................................................................................265

Modifying users with usermod ...................................................................266

Deleting users with userdel ........................................................................268

Understanding Group Accounts ...........................................................................268

Using group accounts .................................................................................269

Creating group accounts .............................................................................270

Managing Users in the Enterprise ........................................................................270

Setting permissions with Access Control Lists .............................................271

Setting ACLs with setfacl ..................................................................272

Setting default ACLs .........................................................................273

Enabling ACLs...................................................................................274

Adding directories for users to collaborate ..................................................276

Creating group collaboration directories (set GID bit) ...........................276

Creating restricted deletion directories (sticky bit) .............................278

Centralizing User Accounts .................................................................................278

Using the Users window .............................................................................279

Using the Authentication Confi guration window ..........................................279

Summary ...........................................................................................................281

Exercises ...........................................................................................................281

Chapter 12: Managing Disks and Filesystems . . . . . . . . . . . . . . . . . . . . . . . . 283

Understanding Disk Storage ................................................................................283

Partitioning Hard Disks ......................................................................................285

Understanding partition tables ...................................................................286

Viewing disk partitions ..............................................................................286

Creating a single-partition disk ..................................................................288

Creating a multiple-partition disk ...............................................................292

Using Logical Volume Management Partitions .......................................................295

Checking an existing LVM ..........................................................................296

Creating LVM logical volumes .....................................................................299

Growing LVM logical volumes ......................................................................300

Mounting Filesystems .........................................................................................301

Supported fi lesystems ................................................................................301

Enabling swap areas ..................................................................................303

Disabling a swap area ................................................................................304

Using the fstab fi le to defi ne mountable fi le systems ....................................305

Using the mount command to mount fi le systems ........................................307

Mounting a disk image in loopback .............................................................308

Using the umount command .......................................................................309

Using the mkfs Command to Create a Filesystem ..................................................310

Summary ...........................................................................................................311

Exercises ...........................................................................................................311

Part IV: Becoming a Linux Server Administrator

CHAPTER 13: Understanding Server Administration . . . . . . . . . . . . . . . . 315

Starting with Server Administration ...................................................................316

Step 1: Install the server ............................................................................316

Step 2: Confi gure the server .......................................................................318

Using confi guration fi les ...................................................................318

Checking the default confi guration ....................................................319

Step 3: Start the server ..............................................................................319

Step 4: Secure the server............................................................................321

Password protection ..........................................................................321

Firewalls ..........................................................................................321

TCP Wrappers ....................................................................................322

SELinux ...........................................................................................322

Security settings in confi guration fi les ...............................................322

Step 5: Monitor the server ..........................................................................322

Confi gure logging..............................................................................322

Run system activity reports ...............................................................323

Keep system software up to date ........................................................323

Check the fi lesystem for signs of crackers ...........................................323

Managing Remote Access with the Secure Shell Service ........................................323

Starting the openssh-server service ............................................................324

Using SSH client tools ................................................................................326

Using ssh for remote login .................................................................326

Using ssh for remote execution ..........................................................328

Copying fi les between systems with scp and rsync ..............................329

Interactive copying with sftp ............................................................332

Using key-based (passwordless) authentication ............................................332

Confi guring System Logging ...............................................................................334

Enabling system logging with rsyslog .........................................................334

Understanding the rsyslog.conf fi le ....................................................335

Understanding the messages log fi le ...................................................337

Setting up and using a loghost with rsyslogd ......................................337

Watching logs with logwatch ......................................................................339

Checking System Resources with sar ....................................................................340

Checking System Space.......................................................................................341

Displaying system space with df .................................................................342

Checking disk usage with du ......................................................................342

Finding disk consumption with fi nd ...........................................................343

Managing Servers in the Enterprise .....................................................................344

Summary ...........................................................................................................344

Exercises ...........................................................................................................345

Chapter 14: Administering Networking . . . . . .. . . . . . . . . . . . . . . . . 347

Confi guring Networking for Desktops...................................................................348

Checking your network interfaces ...............................................................350

Checking your network from NetworkManager ....................................350

Checking your network from the command line ..................................352

Confi guring network interfaces ..................................................................355

Setting IP addresses manually ...........................................................355

Setting IP address aliases ..................................................................356

Setting routes ..................................................................................357

Confi guring a network proxy connection .....................................................358

Confi guring Networking from the Command Line ..................................................360

Editing a connection .................................................................................360

Understanding networking confi guration fi les .............................................362

Network interface fi les ......................................................................363

Other networking fi les.......................................................................365

Setting alias network interfaces .................................................................367

Setting up Ethernet channel bonding .........................................................368

Setting custom routes ................................................................................370

Confi guring Networking in the Enterprise ............................................................371

Confi guring Linux as a router .....................................................................371

Confi guring Linux as a DHCP server ............................................................372

Confi guring Linux as a DNS server ..............................................................372

Confi guring Linux as a proxy server ............................................................373

Summary ........................................................................................................... 374

Exercises ........................................................................................................... 374

Chapter 15: Starting and Stopping Services . . .. . . . . . . . . . . . . . . . . . . . . 377

Understanding the Initialization Daemon (init or systemd) ...................................378

Understanding the classic init daemons ......................................................380

Understanding the Upstart init daemon ......................................................386

Learning Upstart init daemon basics ..................................................386

Learning Upstart’s backward compatibility to SysVinit ........................388

Understanding systemd initialization .........................................................392

Learning systemd basics ....................................................................392

Learning systemd’s backward compatibility to SysVinit........................397

Checking the Status of Services ..........................................................................399

Checking services for SysVinit systems .......................................................400

Checking services for Upstart systems ........................................................401

Checking services for systemd systems .......................................................402

Stopping and Starting Services ...........................................................................403

Stopping and starting SysVinit services ......................................................403

Stopping and starting Upstart services .......................................................405

Stopping and starting systemd services ......................................................406

Stopping a service with systemd ........................................................406

Starting a service with systemd .........................................................406

Restarting a service with systemd ......................................................407

Reloading a service with systemd .......................................................407

Enabling Persistent Services ...............................................................................408

Confi guring persistent services for SysVinit .................................................408

Confi guring persistent services for Upstart ..................................................409

Confi guring persistent services for systemd .................................................410

Enabling a service with systemd ........................................................410

Disabling a service with systemd ....................................................... 411

Confi guring a Default Runlevel or Target Unit ......................................................412

Confi guring the SysVinit default runlevel ....................................................412

Confi guring the default runlevel in Upstart .................................................413

Confi guring the default target unit for systemd ...........................................413

Adding New or Customized Services .....................................................................414

Adding new services to SysVinit .................................................................414

Step 1: Create a new or customized service script fi le ..........................415

Step 2: Add the service script to /etc/rc.d/init.d .................................416

Step 3: Add the service to runlevel directories .................................... 417

Adding new services to Upstart .................................................................. 417

Adding new services to systemd .................................................................419

Step 1: Create a new or customized service confi guration unit fi le ........419

Step 2: Move the service confi guration unit fi le ..................................420

Step 3: Add the service to the Wants directory ....................................420

Summary ...........................................................................................................422

Exercises ...........................................................................................................422

Chapter 16: Confi guring a Print Server . . . . . . . . . . . . . . . . . . . . . . . . . 423

Common UNIX Printing System ...........................................................................423

Setting Up Printers ............................................................................................425

Adding a printer automatically ...................................................................425

Using web-based CUPS administration ........................................................426

Using the Print Settings window ................................................................428

Confi guring local printers with the Print Settings window ...................429

Confi guring remote printers ...............................................................432

Adding a remote CUPS printer ............................................................433

Adding a remote UNIX (LDP/LPR) printer ............................................433

Adding a Windows (SMB) printer ........................................................434

Working with CUPS Printing ...............................................................................435

Confi guring the CUPS server (cupsd.conf) ....................................................436

Starting the CUPS server ............................................................................437

Confi guring CUPS printer options manually .................................................438

Using Printing Commands ...................................................................................439

Printing with lpr .......................................................................................440

Listing status with lpc ...............................................................................440

Removing print jobs with lprm ...................................................................441

Confi guring Print Servers ...................................................................................441

Confi guring a shared CUPS printer ..............................................................442

Confi guring a shared Samba printer ............................................................443

Understanding smb.conf for printing ................................................. 444

Setting up SMB clients ......................................................................445

Summary ...........................................................................................................446

Exercises ...........................................................................................................446

Chapter 17: Confi guring a Web Server . . . . . . . . . . . . . . . . . . . . . . . 449

Understanding the Apache Web Server .................................................................449

Getting and Installing Your Web Server ...............................................................450

Understanding the httpd package ...............................................................450

Installing Apache ......................................................................................453

Starting Apache .................................................................................................454

Securing Apache .......................................................................................455

Apache fi le permissions and ownership ...............................................455

Apache and iptables ..........................................................................455

Apache and SELinux ..........................................................................456

Understanding the Apache confi guration fi les .............................................457

Using directives ................................................................................457

Understanding default settings ..........................................................460

Adding a virtual host to Apache .................................................................462

Allowing users to publish their own web content .........................................464

Securing your web traffi c with SSL/TLS ......................................................465

Understanding how SSL is confi gured .................................................467

Generating an SSL key and self-signed certifi cate ................................469

Generating a certifi cate signing request .............................................470

Troubleshooting Your Web Server ........................................................................471

Checking for confi guration errors ...............................................................472

Accessing forbidden and server internal errors ............................................ 474

Summary ...........................................................................................................475

Exercises ...........................................................................................................475

Chapter 18: Confi guring an FTP Server . . . . . . . . .  . . . . . . . . . . . . 477

Understanding FTP .............................................................................................477

Installing the vsftpd FTP Server ..........................................................................479

Starting the vsftpd Service.................................................................................480

Securing Your FTP Server ....................................................................................483

Opening up your fi rewall for FTP .................................................................483

Allowing FTP access in TCP wrappers ...........................................................486

Confi guring SELinux for your FTP server .....................................................486

Relating Linux fi le permissions to vsftpd ....................................................488

Confi guring Your FTP Server ...............................................................................488

Setting up user access ...............................................................................488

Allowing uploading ...................................................................................489

Setting up vsftpd for the Internet ..............................................................491

Using FTP Clients to Connect to Your Server .........................................................492

Accessing an FTP server from Firefox ..........................................................493

Accessing an FTP server with the lftp command ..........................................493

Using the gFTP client .................................................................................495

Summary ...........................................................................................................496

Exercises ...........................................................................................................497

Chapter 19: Confi guring a Windows File Sharing (Samba) Server . .. . . . . . . 499

Understanding Samba ........................................................................................499

Installing Samba ................................................................................................500

Starting and Stopping Samba ..............................................................................502

Starting the Samba (smb) service ...............................................................503

Starting the NetBIOS (nmbd) name server ...................................................505

Stopping the Samba (smb) and NetBIOS (nmb) services .................................506

Securing Samba .................................................................................................506

Confi guring fi rewalls for Samba ..................................................................507

Confi guring SELinux for Samba ...................................................................508

Setting SELinux Booleans for Samba...................................................508

Setting SELinux fi le contexts for Samba .............................................510

Confi guring Samba host/user permissions ...................................................510

Confi guring Samba ............................................................................................. 511

Using system-confi g-samba ........................................................................ 511

Choosing Samba server settings ......................................................... 511

Confi guring Samba user accounts .......................................................512

Creating a Samba shared folder ..........................................................513

Checking the Samba share .................................................................514

Confi guring Samba in the smb.conf fi le .......................................................516

Confi guring the [global] section .........................................................516

Confi guring the [homes] section ........................................................518

Confi guring the [printers] section ......................................................519

Creating custom shared directories ....................................................519

Accessing Samba Shares .....................................................................................521

Accessing Samba shares in Linux ................................................................522

Accessing Samba shares in Windows ...........................................................524

Using Samba in the Enterprise ............................................................................525

Summary ...........................................................................................................525

Exercises ...........................................................................................................526

Chapter 20: Confi guring an NFS File Server . . . . . . . . . . . . . . . . 527

Installing an NFS Server .....................................................................................529

Starting the NFS service .....................................................................................530

Sharing NFS Filesystems .....................................................................................531

Confi guring the /etc/exports fi le ................................................................532

Hostnames in /etc/exports ................................................................533

Access options in /etc/exports ...........................................................534

User mapping options in /etc/exports ................................................534

Exporting the shared fi lesystems ................................................................535

Securing Your NFS Server ...................................................................................536

Opening up your fi rewall for NFS ................................................................537

Allowing NFS access in TCP wrappers ...........................................................539

Confi guring SELinux for your NFS server .....................................................539

Using NFS Filesystems ........................................................................................540

Viewing NFS shares ....................................................................................540

Manually mounting an NFS fi lesystem .........................................................541

Mounting an NFS fi lesystem at boot time ....................................................542

Mounting noauto fi lesystems .............................................................543

Using mount options .........................................................................543

Using autofs to mount NFS fi lesystems on demand .......................................545

Automounting to the /net directory ...................................................546

Automounting home directories .........................................................547

Unmounting NFS fi lesystems ...............................................................................549

Summary ...........................................................................................................549

Exercises ...........................................................................................................550

Chapter 21: Troubleshooting Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 551

Boot-Up Troubleshooting ....................................................................................551

Understanding Startup Methods .................................................................552

Starting with System V init scripts ....................................................552

Starting with systemd .......................................................................553

Starting with Upstart ........................................................................554

Starting from the fi rmware (BIOS or UEFI) ..................................................554

Troubleshooting BIOS setup ...............................................................555

Troubleshooting boot order ................................................................556

Troubleshooting the GRUB boot loader ........................................................557

Starting the kernel ....................................................................................559

Troubleshooting the initialization system .........................................560

Troubleshooting System V initialization .............................................560

Troubleshooting rc.sysinit .................................................................561

Troubleshooting runlevel processes ....................................................562

Troubleshooting systemd initialization ..............................................566

Troubleshooting Software Packages .....................................................................568

Fixing RPM databases and cache .................................................................572

Troubleshooting Networking ...............................................................................573

Troubleshooting outgoing connections ........................................................573

View network interfaces .................................................................... 574

Check physical connections ............................................................... 574

Check routes .....................................................................................575

Check hostname resolution ................................................................576

Troubleshooting incoming connections .......................................................577

Check if the client can reach your system at all...................................577

Check if the service is available to the client ......................................578

Check the fi rewall on the server .........................................................578

Check the service on the server .........................................................579

Troubleshooting Memory ....................................................................................580

Uncovering memory issues .........................................................................581

Checking for memory problems ..........................................................583

Dealing with memory problems ..........................................................584

Troubleshooting in Rescue Mode .........................................................................585

Summary ...........................................................................................................587

Exercises ...........................................................................................................587

Part V: Learning Linux Security Techniques

Chapter 22: Understanding Basic Linux Security . . . . .  . . . . . . . . . . . 591

Understanding Security Basics ............................................................................591

Implementing physical security ..................................................................591

Implementing disaster recovery..................................................................592

Securing user accounts ..............................................................................593

One user per user account ..................................................................593

Limit access to the root user account .................................................594

Setting expiration dates on temporary accounts .................................594

Removing unused user accounts.........................................................595

Securing passwords ...................................................................................596

Choosing good passwords...................................................................597

Setting and changing passwords ........................................................598

Enforcing best password practices ......................................................599

Understanding the password fi les and password hashes .......................601

Securing the fi lesystem .............................................................................603

Managing dangerous fi lesystem permissions .......................................603

Securing the password fi les ...............................................................604

Locking down the fi lesystem .............................................................606

Managing software and services .................................................................607

Updating software packages ..............................................................607

Keeping up with security advisories ...................................................607

Advanced implementation ..........................................................................608

Monitoring Your Systems ....................................................................................608

Monitoring log fi les ...................................................................................608

Monitoring user accounts ...........................................................................612

Detecting counterfeit new accounts and privileges ..............................612

Detecting bad account passwords .......................................................614

Monitoring the fi lesystem ..........................................................................615

Verifying software packages ..............................................................615

Scanning the fi lesystem ....................................................................616

Detecting viruses and rootkits ...........................................................618

Auditing and Reviewing Linux ............................................................................622

Conducting compliance reviews ..................................................................623

Conducting security reviews ......................................................................623

Summary ...........................................................................................................624

Exercises ...........................................................................................................624

Chapter 23: Understanding Advanced Linux Security . . . . . . . . . . . . . 627

Implementing Linux Security with Cryptography .................................................627

Understanding hashing ..............................................................................628

Understanding encryption/decryption ........................................................630

Understanding cryptographic ciphers .................................................630

Understanding cryptographic cipher keys ...........................................631

Understanding digital signatures .......................................................637

Implementing Linux cryptography ..............................................................639

Ensuring fi le integrity .......................................................................639

Encrypting a Linux fi lesystem ...........................................................640

Encrypting a Linux directory .............................................................642

Encrypting a Linux fi le......................................................................645

Encrypting Linux with miscellaneous tools .........................................645

Using Encryption from the Desktop ....................................................646

Implementing Linux Security with PAM ...............................................................648

Understanding the PAM authentication process ...........................................649

Understanding PAM contexts .............................................................650

Understanding PAM control fl ags ........................................................651

Understanding PAM modules ..............................................................652

Understanding PAM system event confi guration fi les ...........................653

Administering PAM on your Linux system ...................................................654

Managing PAM-aware application confi guration fi les ...........................654

Managing PAM system event confi guration fi les ..................................655

Implementing resources limits with PAM ............................................657

Implementing time restrictions with PAM ...........................................658

Enforcing good passwords with PAM ...................................................660

Encouraging sudo use with PAM .........................................................664

Locking accounts with PAM ...............................................................665

Obtaining more information on PAM ...........................................................667

Summary ...........................................................................................................668

Exercises ...........................................................................................................668

Chapter 24: Enhancing Linux Security with SELinux . . .  . . . . . . . . . . . . . . 669

Understanding SELinux Benefi ts .........................................................................669

Understanding How SELinux Works .....................................................................671

Understanding type enforcement ................................................................671

Understanding multi-level security .............................................................672

Implementing SELinux security models .......................................................673

Understanding SELinux operational modes .........................................673

Understanding SELinux security contexts ...........................................674

Understanding SELinux policy types ..................................................677

Understanding SELinux policy rule packages ......................................678

Confi guring SELinux ..........................................................................................679

Setting the SELinux mode ..........................................................................680

Setting the SELinux policy type .................................................................682

Managing SELinux security contexts ...........................................................683

Managing the user security context ...................................................684

Managing the fi le security context .....................................................684

Managing the process security context ...............................................685

Managing SELinux policy rule packages ......................................................686

Managing SELinux via booleans ..................................................................688

Monitoring and Troubleshooting SELinux .............................................................689

Understanding SELinux logging ..................................................................689

Reviewing SELinux messages in the audit log......................................690

Reviewing SELinux messages in the messages log ................................690

Troubleshooting SELinux logging ................................................................691

Troubleshooting common SELinux problems ................................................692

Using a nonstandard directory for a service ........................................692

Using a nonstandard port for a service ...............................................693

Moving fi les and losing security context labels ...................................693

Booleans set incorrectly ....................................................................694

Putting It All Together .......................................................................................694

Obtaining More Information on SELinux ..............................................................695

Summary ...........................................................................................................695

Exercises ...........................................................................................................696

Chapter 25: Securing Linux on a Network . . . . . . . . . . . . . . . . . . . . 699

Auditing Network Services ..................................................................................699

Evaluating access to network services with nmap ........................................701

Using nmap to audit your network services advertisements ..........................704

Controlling access to network services ........................................................708

Working with Firewalls .......................................................................................710

Understanding fi rewalls .............................................................................710

Implementing fi rewalls ..............................................................................711

Starting with fi rewalld ......................................................................712

Understanding the iptables utility .....................................................713

Using the iptables utility...................................................................716

Summary ...........................................................................................................724

Exercises ...........................................................................................................724

Part VI: Extending Linux into the Cloud

Chapter 26: Using Linux for Cloud Computing . . . . . . . . . .  . . . . . . . . . . 729

Overview of Linux and Cloud Computing ..............................................................729

Cloud hypervisors (a.k.a. compute nodes) ....................................................730

Cloud controllers .......................................................................................730

Cloud storage ............................................................................................731

Cloud authentication .................................................................................731

Cloud deployment and confi guration ...........................................................732

Cloud platforms .........................................................................................732

Trying Basic Cloud Technology ............................................................................732

Setting Up a Small Cloud ....................................................................................734

Confi guring hypervisors .............................................................................735

Step 1: Get Linux software ................................................................735

Step 2: Check your computers ............................................................735

Step 3: Install Linux on hypervisors ...................................................736

Step 4: Start services on the hypervisors ............................................737

Step 5: Edit /etc/hosts or set up DNS ..................................................738

Confi guring storage ...................................................................................738

Step 1: Install Linux software ............................................................738

Step 2: Confi gure NFS share ...............................................................739

Step 3: Start the NFS service ..............................................................739

Step 4: Mount the NFS share on the hypervisors ..................................740

Creating virtual machines ..........................................................................740

Step 1: Get images to make virtual machines ...................................... 741

Step 2: Check the network bridge ....................................................... 741

Step 3: Start Virtual Machine Manager (virt-manager) ......................... 741

Step 4: Check connection details ........................................................742

Step 5: Create a new virtual machine .................................................743

Managing virtual machines ........................................................................744

Migrating virtual machines ........................................................................745

Step 1: Identify other hypervisors......................................................745

Step 2: Migrate running VM to another hypervisor ..............................746

Summary ........................................................................................................... 747

Exercises ........................................................................................................... 747

Chapter 27: Deploying Linux to the Cloud. . . . . . .. . . . . . . . . . . . . . . . . 749

Getting Linux to Run in a Cloud .......................................................................... 749

Creating Linux Images for Clouds ........................................................................751

Confi guring and running a cloud-init cloud instance ....................................751

Investigating the cloud instance ................................................................753

Cloning the cloud instance .........................................................................754

Trying an Ubuntu cloud image ...................................................................756

Expanding your cloud-init confi guration .....................................................757

Adding ssh keys with cloud-init .........................................................757

Adding network interfaces with cloud-init ..........................................758

Adding software with cloud-init ........................................................758

Using cloud-init in enterprise computing ....................................................759

Using OpenStack to Deploy Cloud Images .............................................................760

Starting from the OpenStack Dashboard ...................................................... 761

Confi guring your OpenStack virtual network ...................................... 761

Confi guring keys for remote access .....................................................763

Launching a virtual machine in OpenStack .........................................764

Accessing the virtual machine via ssh ................................................765

Using Amazon EC2 to Deploy Cloud Images ...........................................................765

Summary ...........................................................................................................766

Part VII: Appendixes

Appendix A: Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 771

Appendix B: Exercise Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 781

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839

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