Linux Bible

Chris Negus is an instructor for Red Hat, Inc. and the author of dozens of Linux and UNIX books, including Red Hat Linux Bible (all editions), CentOS Bible, Fedora Bible, Ubuntu Linux Toolbox, Linux Troubleshooting Bible, Linux Toys, and Linux Toys II. Christine Bresnahan has over 25 years' experience as a system administrator. She is an adjunct professor at Ivy Tech Community College, teaching Linux system administration, Linux security, and Windows security classes. She co-authored the Linux Command Line and Shell Scripting Bible, 2nd Edition.

Introduction xxxiii Part I: Getting Started 1 Chapter 1: Starting with Linux 3 Understanding What Linux Is 4 Understanding How Linux Differs from Other Operating Systems 5 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 9 GNU transitions UNIX to freedom 11 BSD loses some steam 12 Linus builds the missing piece 13 OSI open source definition 14 Understanding How Linux Distributions Emerged 15 Choosing a Red Hat distribution 16 Using Red Hat Enterprise Linux 17 Using Fedora 18 Choosing Ubuntu or another Debian distribution 18 Finding Professional Opportunities with Linux Today 19 Understanding how companies make money with Linux 20 Becoming Red Hat Certified 21 RHCSA topics 22 RHCE topics 23 Summary 24 Chapter 2: Creating the Perfect Linux Desktop 27 Understanding Linux Desktop Technology 28 Starting with the Fedora GNOME Desktop Live CD 30 Using the GNOME 3 Desktop 31 After the computer boots up 31 Navigating with the mouse 32 Navigating with the keyboard 36 Setting up the GNOME 3 desktop 38 Extending the GNOME 3 desktop 39 Using GNOME shell extensions 39 Using the GNOME Tweak Tool 40 Starting with desktop applications 42 Managing fi les and folders with Nautilus 42 Installing and managing additional software 44 Playing music with Rhythmbox 45 Stopping the GNOME 3 desktop 46 Using the GNOME 2 Desktop 46 Using the Metacity window manager 48 Changing GNOME appearance 49 Using the GNOME panels 50 Using the Applications and System menus 51 Adding an applet 51 Adding another panel 52 Adding an application launcher 52 Adding a drawer 53 Changing panel properties 53 3D effects with AIGLX 54 Summary 57 Exercises 57 Part II: Becoming a Linux Power User 59 Chapter 3: Using the Shell 61 About Shells and Terminal Windows 62 Using the shell prompt 63 Using a terminal window 64 Using virtual consoles 65 Choosing Your Shell 65 Running Commands 66 Understanding command syntax 67 Locating commands 70 Recalling Commands Using Command History 72 Command-line editing 73 Command-line completion 75 Command-line recall 76 Connecting and Expanding Commands 78 Piping between commands 78 Sequential commands 79 Background commands 79 Expanding commands 80 Expanding arithmetic expressions 80 Expanding variables 81 Using Shell Variables 81 Creating and using aliases 83 Exiting the shell 84 Creating Your Shell Environment 84 Confi guring your shell 84 Setting your prompt 85 Adding environment variables 87 Getting Information About Commands 88 Summary 90 Exercises 90 Chapter 4: Moving Around the Filesystem 93 Using Basic Filesystem Commands 96 Using Metacharacters and Operators 98 Using file-matching metacharacters 98 Using file-redirection metacharacters 99 Using brace expansion characters 101 Listing Files and Directories 101 Understanding File Permissions and Ownership 105 Changing permissions with chmod (numbers)107 Changing permissions with chmod (letters) 107 Setting default file permission with umask 108 Changing file ownership 109 Moving, Copying, and Removing Files 110 Summary 111 Exercises 112 Chapter 5: Working with Text Files 113 Editing Files with vim and vi 113 Starting with vi 115 Adding text 115 Moving around in the text 116 Deleting, copying, and changing text 117 Pasting (putting) text 118 Repeating commands 118 Exiting vi 118 Skipping around in the file 119 Searching for text 120 Using ex mode 120 Learning more about vi and vim 120 Finding Files 121 Using locate to find files by name 121 Searching for files with find 122 Finding files by name 123 Finding files by size 124 Finding files by user 124 Finding files by permission 125 Finding files by date and time 126 Using not and or when finding files 126 Finding files and executing commands 127 Searching in files with grep 128 Summary 129 Exercises 130 Chapter 6: Managing Running Processes 131 Understanding Processes 131 Listing Processes 132 Listing processes with ps 132 Listing and changing processes with top 134 Listing processes with System Monitor 135 Managing Background and Foreground Processes 137 Starting background processes138 Using foreground and background commands 139 Killing and Renicing Processes 140 Killing processes with kill and killall 140 Using kill to signal processes by PID 141 Using killall to signal processes by name 141 Setting processor priority with nice and renice 142 Summary 143 Exercises 143 Chapter 7: Writing Simple Shell Scripts 145 Understanding Shell Scripts 145 Executing and debugging shell scripts 146 Understanding shell variables 147 Special shell positional parameters 148 Reading in parameters 149 Parameter expansion in bash 149 Performing arithmetic in shell scripts 150 Using programming constructs in shell scripts 151 The if then statements 151 The case command 154 The for do loop 155 The while do and until do loops 156 Trying some useful text manipulation programs 157 The general regular expression parser 157 Remove sections of lines of text (cut) 158 Translate or delete characters (tr) 158 The stream editor (sed) 158 Using simple shell scripts 159 Telephone list 159 Backup script 160 Summary 161 Exercises 161 Part III: Becoming a Linux System Administrator 163 Chapter 8: Learning System Administration 165 Understanding System Administration 165 Using Graphical Administration Tools 167 Using the root User Account 169 Becoming root from the shell (su command) 170 Allowing administrative access via the GUI 171 Gaining administrative access with sudo 172 Exploring Administrative Commands, Configuration Files, and Log Files 174 Administrative commands 174 Administrative configuration files 175 Administrative log files 179 Using Other Administrative Accounts 180 Checking and Configuring Hardware 181 Checking your hardware182 Managing removable hardware 184 Working with loadable modules 186 Listing loaded modules 187 Loading modules 187 Removing modules 188 Summary 188 Exercises 189 Chapter 9: Installing Linux 191 Choosing a Computer 192 Installing Fedora from a Live CD 193 Installing Red Hat Enterprise Linux from Installation Media 199 Installing Linux in the Enterprise 202 Exploring Common Installation Topics 204 Upgrading or installing from scratch 204 Dual booting 205 Installing Linux to run virtually 206 Using installation boot options 207 Boot options for disabling features 207 Boot options for video problems 208 Boot options for special installation types 208 Boot options for kickstarts and remote repositories 209 Miscellaneous boot options 210 Using specialized storage 210 Partitioning hard drives 211 Understanding different partition types 212 Partitioning during Fedora installation 212 Reasons for different partitioning schemes 216 Tips for creating partitions 216 Using the GRUB boot loader 218 Using GRUB Legacy (version 1) 218 Using GRUB 2 223 Summary 224 Exercises 225 Chapter 10: Getting and Managing Software 227 Managing Software with PackageKit 227 Enabling repositories and getting updates 228 Searching for packages 229 Installing and removing packages 230 Going beyond PackageKit 231 Understanding Linux RPM Software Packaging 231 Understanding RPM packaging 232 What is in an RPM? 233 Where do RPMs come from? 234 Installing RPMs 234 Managing RPM Packages with YUM 235 Understanding how yum works 235 1 Checking /etc/yumconf 236 2 Checking /etc/sysconfig/rhn/up2date (RHEL only) 237 3 Checking /etc/yumreposd/repo files 237 4 Downloading RPM packages and metadata from a YUM repository 238 5 RPM packages installed to Linux file system 238 6 Store YUM repository metadata to local RPM database 238 Using YUM with third-party software repositories 239 Managing software with the YUM command 240 Searching for packages 240 Installing and removing packages 242 Updating packages 243 Updating groups of packages 244 Maintaining your RPM package database and cache 245 Downloading RPMs from a yum repository 246 Installing, Querying, and Verifying Software with the rpm Command 246 Installing and removing packages with rpm 247 Querying rpm information 247 Verifying RPM packages 249 Managing Software in the Enterprise 250 Summary 251 Exercises 252 Chapter 11: Managing User Accounts 253 Creating User Accounts 253 Adding users with useradd 256 Setting user defaults 259 Modifying users with usermod 260 Deleting users with userdel 261 Understanding Group Accounts 262 Using group accounts 262 Creating group accounts 263 Managing Users in the Enterprise 264 Setting permissions with Access Control Lists 265 Setting ACLs with setfacl 265 Setting default ACLs 267 Enabling ACLs 268 Adding directories for users to collaborate 270 Creating group collaboration directories (set GID bit) 270 Creating restricted deletion directories (sticky bit) 271 Centralizing User Accounts 272 Using the Authentication Configuration window 273 Summary 274 Exercises 275 Chapter 12: Managing Disks and Filesystems 277 Understanding Disk Storage 277 Partitioning Hard Disks 279 Viewing disk partitions 280 Creating a single-partition disk 281 Creating a multiple-partition disk 284 Using Logical Volume Management Partitions 288 Checking an existing LVM 288 Creating LVM logical volumes 291 Growing LVM logical volumes 293 Mounting Filesystems 293 Supported filesystems 294 Enabling swap areas 296 Disabling swap area 297 Using the fstab file to define mountable file systems 297 Using the mount command to mount file systems 300 Mounting a disk image in loopback 301 Using the umount command 301 Using the mkfs Command to Create a Filesystem 302 Summary 303 Exercises 303 Part IV: Becoming a Linux Server Administrator 305 Chapter 13: Understanding Server Administration 307 Starting with Server Administration 308 Step 1: Install the server 308 Step 2: Configure the server 310 Using configuration files 310 Checking the default configuration 310 Step 3: Start the server 311 Step 4: Secure the server 312 Password protection 313 Firewalls 313 TCP Wrappers313 SELinux 313 Security settings in configuration files 314 Step 5: Monitor the server 314 Confi gure logging 314 Run system activity reports 314 Keep system software up to date 314 Check the fi lesystem for signs of crackers 315 Managing Remote Access with the Secure Shell Service 315 Starting the openssh-server service 316 Using SSH client tools 317 Using ssh for remote login 318 Using ssh for remote execution 319 Copying files between systems with scp and rsync 320 Interactive copying with sftp 323 Using key-based (passwordless) authentication 323 Confi guring System Logging 325 Enabling system logging with rsyslog 325 Understanding the rsyslogconf file 326 Understanding the messages log file 327 Setting up and using a loghost with rsyslogd 328 Watching logs with logwatch 329 Checking System Resources with sar 330 Checking System Space 332 Displaying system space with df 332 Checking disk usage with du 333 Finding disk consumption with find 333 Summary 334 Exercises 335 Chapter 14: Administering Networking 337 Configuring Networking for Desktops 338 Checking your network interfaces 340 Checking your network from NetworkManager 340 Checking your network from the command line 342 Configuring network interfaces 345 Configuring a network proxy connection 347 Configuring Networking for Servers 348 Using system-config-network 349 Choosing device configuration 350 Choosing DNS configuration 351 Understanding networking configuration files 351 Network interface files 352 Other networking files 353 Setting alias network interfaces 356 Setting up Ethernet channel bonding 357 Setting custom routes 358 Configuring Networking in the Enterprise 359 Configuring Linux as a router 359 Configuring Linux as a DHCP server 360 Configuring Linux as a DNS server 361 Configuring Linux as a proxy server 361 Configuring VLANs in Linux 362 Summary 363 Exercises 363 Chapter 15: Starting and Stopping Services 365 Understanding the Linux init Daemon 365 Understanding the classic init daemons 367 Understanding the Upstart init daemon 375 Learning Upstart init daemon basics 375 Learning Upstart s backward compatibility to SysVinit 378 Understanding systemd init 382 Learning systemd basics 382 Learning systemd s backward compatibility to SysVinit 388 Auditing Services 390 Auditing the classic SysVinit daemon 391 Auditing the Upstart init daemon 392 Auditing the systemd init393 Stopping and Starting Services 394 Stopping and starting the classic SysVinit daemon 395 Stopping and starting the Upstart init daemon 396 Stopping and starting the systemd daemon 397 Stopping a service with systemd 397 Starting a service with systemd 398 Restarting a service with systemd 398 Reloading a service with systemd 399 Configuring Persistent Services 400 Configuring the classic SysVinit daemon persistent services 400 Configuring Upstart init daemon persistent services 401 Configuring systemd init persistent services 402 Enabling a service with systemd 402 Disabling (removing) a service with systemd 402 Configuring a Default runlevel or target unit 404 Configuring the classic SysVinit daemon default runlevel 404 Configuring the Upstart init daemon default runlevel 404 Configuring the systemd init default target unit 405 Adding New or Customized Services 406 Adding new services to classic SysVinit daemon 406 Step 1: Create a new or customized service script file 406 Step 2: Move the service script 407 Step 3: Add the service to runlevels 407 Adding new services to the Upstart init daemon 408 Adding new services to systemd init 410 Step 1: Create a new or customized service configuration unit file 410 Step 2: Move the service configuration unit file 411 Step 3: Add the service to the Wants directory 412 Summary 413 Exercises 413 Chapter 16: Configuring a Print Server 415 Common UNIX Printing System 415 Setting Up Printers 417 Adding a printer automatically 417 Using web-based CUPS administration 418 Using the Printer Configuration window 420 Configuring local printers with the Printer Configuration window 421 Configuring remote printers 424 Adding a remote CUPS printer 425 Adding a remote UNIX (LDP/LPR) printer 425 Adding a Windows (SMB) printer 426 Working with CUPS Printing 427 Configuring the CUPS server (cupsdconf) 427 Starting the CUPS server 429 Configuring CUPS printer options manually 429 Using Printing Commands 431 Printing with lpr 431 Listing status with lpc 431 Removing print jobs with lprm 432 Configuring Print Servers 433 Configuring a shared CUPS printer 433 Configuring a shared Samba printer 435 Understanding smbconf for printing 435 Setting up SMB clients 436 Summary 437 Exercises 437 Chapter 17: Configuring a Web Server 439 Understanding the Apache Web Server 439 Getting and Installing Your Web Server 440 Understanding the httpd package 440 Installing Apache 443 Starting Apache 443 Securing Apache 444 Apache fi le permissions and ownership 445 Apache and iptables 445 Apache and SELinux 445 Understanding the Apache configuration files 446 Using directives 447 Understanding default settings 449 Adding a virtual host to Apache 451 Allowing users to publish their own web content 453 Securing your web traffic with SSL/TLS 455 Understanding how SSL is configured 456 Generating an SSL key and self-signed certificate 458 Generating a certificate signing request 459 Troubleshooting Your Web Server 460 Checking for configuration errors 460 Accessing forbidden and server internal errors 463 Summary 464 Exercises 464 Chapter 18: Configuring an FTP Server 467 Understanding FTP 467 Installing the vsftpd FTP Server 469 Starting the vsftpd Service 470 Securing Your FTP Server 472 Opening up your fi rewall for FTP 473 Allowing FTP access in TCP wrappers 474 Configuring SELinux for your FTP server 475 Relating Linux file permissions to vsftpd 476 Configuring Your FTP Server 477 Setting up user access 477 Allowing uploading 478 Setting up vsftpd for the Internet 479 Using FTP Clients to Connect to Your Server 481 Accessing an FTP server from Firefox 481 Accessing an FTP server with the lftp command 482 Using the gFTP client 484 Summary 485 Exercises 485 Chapter 19: Configuring a Windows File Sharing (Samba) Server 487 Understanding Samba 487 Installing Samba 488 Starting and Stopping Samba 490 Starting the Samba (smb) service 490 Starting the NetBIOS (nmbd) name server 492 Stopping the Samba (smb) and NetBIOS (nmb) services 493 Securing Samba 494 Configuring firewalls for Samba 495 Configuring SELinux for Samba 496 Setting SELinux Booleans for Samba 496 Setting SELinux file contexts for Samba 497 Configuring Samba host/user permissions 498 Configuring Samba 498 Using system-config-samba 498 Choosing Samba server settings 499 Configuring Samba user accounts 500 Creating a Samba shared folder 501 Checking the Samba share 502 Configuring Samba in the smbconf file 503 Configuring the [global] section 504 Configuring the [homes] section505 Configuring the [printers] section 506 Creating custom shared directories 507 Accessing Samba Shares 509 Accessing Samba shares in Linux 509 Accessing Samba shares in Windows 512 Using Samba in the Enterprise 512 Summary 513 Exercises 513 Chapter 20: Configuring an NFS File Server 515 Installing an NFS Server 517 Starting the NFS service 518 Sharing NFS Filesystems 519 Configuring the /etc/exports file 520 Hostnames in /etc/exports 521 Access options in /etc/exports 522 User mapping options in /etc/exports 522 Exporting the shared filesystems 523 Securing Your NFS Server 523 Opening up your fi rewall for NFS 524 Allowing NFS access in TCP wrappers 525 Confi guring SELinux for your NFS server 526 Using NFS Filesystems 527 Viewing NFS shares 527 Manually mounting an NFS filesystem 527 Mounting an NFS filesystem at boot time 528 Mounting noauto filesystems 529 Using mount options 530 Using autofs to mount NFS filesystems on demand 532 Automounting to the /net directory 532 Automounting home directories 533 Unmounting NFS fi esystems 535 Summary 536 Exercises 536 Chapter 21: Troubleshooting Linux 539 Boot-Up Troubleshooting 539 Starting from the BIOS 540 Troubleshooting BIOS setup 541 Troubleshooting boot order 542 Troubleshooting the GRUB boot loader 542 Starting the kernel 545 Troubleshooting the init process 546 Troubleshooting rcsysinit 546 Troubleshooting runlevel processes 547 Troubleshooting Software Packages 551 Fixing RPM databases and cache 555 Troubleshooting Networking 556 Troubleshooting outgoing connections 556 View network interfaces 557 Check physical connections557 Check routes 557 Check hostname resolution 558 Troubleshooting incoming connections 560 Check if the client can reach your system at all 560 Check if the service is available to the client 560 Check the firewall on the server 561 Check the service on the server 562 Troubleshooting Memory 563 Uncovering memory issues 563 Checking for memory problems 566 Dealing with memory problems 567 Troubleshooting in Rescue Mode 568 Summary 569 Exercises 570 Part V: Learning Linux Security Techniques 571 Chapter 22: Understanding Basic Linux Security 573 Introducing the Security Process Lifecycle 573 Examining the Planning Phase 575 Choosing an access control model 575 Discretionary Access Control 575 Mandatory Access Control 576 Role Based Access Control 576 Using security checklists 577 Access Control Matrix 577 Industry security checklists 578 Entering the Implementation Phase 578 Implementing physical security 578 Implementing disaster recovery 579 Securing user accounts 580 One user per user account 580 No logins to the root account 581 Setting expiration dates on temporary accounts 582 Removing unused user accounts 583 Securing passwords 585 Choosing good passwords 585 Setting and changing passwords 586 Enforcing best password practices 587 Understanding the password files and password hashes 590 Securing the filesystem 591 Managing dangerous filesystem permissions 591 Securing the password files 592 Locking down the filesystem 594 Managing software and services 595 Removing unused software and services 595 Updating software packages 596 Advanced implementation 596 Working in the Monitoring Phase 596 Monitoring log files 596 Monitoring user accounts 600 Detecting counterfeit new accounts and privileges 600 Detecting bad account passwords 602 Monitoring the filesystem 603 Verifying software packages 604 Scanning the filesystem 605 Detecting viruses and rootkits 606 Detecting an intrusion 608 Working in the Audit/Review Phase 611 Conducting compliance reviews 611 Conducting security reviews 612 Summary 612 Exercises 613 Chapter 23: Understanding Advanced Linux Security 615 Implementing Linux Security with Cryptography 615 Understanding hashing 616 Understanding encryption/decryption 618 Understanding cryptographic ciphers 618 Understanding cryptographic cipher keys 619 Understanding digital signatures 625 Implementing Linux cryptography 627 Ensuring file integrity 627 Encrypting a Linux filesystem 628 Encrypting a Linux directory 630 Encrypting a Linux file 633 Encrypting Linux miscellaneous 634 Implementing Linux Security with PAM 635 Understanding the PAM authentication process 636 Understanding PAM contexts 638 Understanding PAM control flags 638 Understanding PAM modules 639 Understanding PAM system event configuration files 640 Administering PAM on your Linux system 641 Managing PAM-aware application configuration files 641 Managing PAM system event confi guration files 642 Implementing resources limits with PAM 644 Implementing time restrictions with PAM 646 Encouraging sudo use with PAM 652 Locking accounts with PAM 653 Obtaining more information on PAM 655 Summary 656 Exercises 656 Chapter 24: Enhancing Linux Security with SELinux 659 Understanding SELinux Benefits 659 Understanding How SELinux Works 661 Understanding Type Enforcement 661 Understanding Multi-Level Security 662 Implementing SELinux security models 663 Understanding SELinux Operational Modes 663 Understanding SELinux security contexts 664 Understanding SELinux Policy types 667 Understanding SELinux Policy rule packages 668 Configuring SELinux 669 Setting the SELinux Operational Mode 670 Setting the SELinux Policy type 672 Managing SELinux security contexts 673 Managing the user security context 674 Managing the file security context 675 Managing the process security context 676 Managing SELinux policy rule packages 676 Managing SELinux via Booleans 678 Monitoring and Troubleshooting SELinux 679 Understanding SELinux logging 679 Reviewing SELinux messages in the audit log 680 Reviewing SELinux messages in the messages log 680 Troubleshooting SELinux logging 682 Troubleshooting common SELinux problems 682 Using a non-standard directory for a service 683 Using a non-standard port for a service 683 Moving files and losing security context labels 684 Booleans set incorrectly 684 Putting It All Together 684 Obtaining More Information on SELinux 685 Summary 686 Exercises 686 Chapter 25: Securing Linux on a Network 689 Auditing Network Services 690 Evaluating access to network services 692 Using nmap to create a network services list 692 Using nmap to audit your network services advertisements 695 Controlling access to network services 699 Working with Firewalls 702 Understanding firewalls 702 Implementing firewalls 703 Understanding the iptables utility 703 Using the iptables utility 707 Summary 715 Exercises 716 Part VI: Appendixes 717 Appendix A: Media 719 Getting Fedora 720 Getting Red Hat Enterprise Linux 721 Getting Ubuntu 722 Creating Linux CDs and DVDs 724 Burning CDs/DVDs in Windows 724 Burning CDs/DVDs on a Mac OS X system 724 Burning CDs/DVDs in Linux 725 Burning CDs from a Linux desktop 725 Burning CDs from a Linux command line 726 Booting Linux from a USB Drive 727 Appendix B: Exercise Answers 729 Chapter 2: Creating the Perfect Linux Desktop 729 Chapter 3: Using the Shell 732 Chapter 4: Moving Around the Filesystem 734 Chapter 5: Working with Text Files 735 Chapter 6: Managing Running Processes 737 Chapter 7: Writing Simple Shell Scripts 738 Chapter 8: Learning System Administration 740 Chapter 9: Installing Linux 743 Chapter 10: Getting and Managing Software 745 Chapter 11: Managing User Accounts 746 Chapter 12: Managing Disks and Filesystems 750 Chapter 13: Understanding Server Administration 752 Chapter 14: Administering Networking 755 Chapter 15: Starting and Stopping Services 758 Chapter 16: Configuring a Print Server 761 Chapter 17: Configuring a Web Server 763 Chapter 18: Configuring an FTP Server 766 Chapter 19: Configuring a Windows File Sharing (Samba) Server 769 Chapter 20: Configuring an NFS File Server 772 Chapter 21: Troubleshooting Linux 774 Chapter 22: Understanding Basic Linux Security 776 Chapter 23: Understanding Advanced Linux Security 777 Chapter 24: Enhancing Linux Security with SELinux 779 Chapter 25: Securing Linux on a Network 781 Index 783