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Linux System Administration, Second Edition (Craig Hunt Linux Library) PDF

656 Pages·2002·6.98 MB·English
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Linux System Administration Table of Contents Linux System Administration, Second Edition...............................................................................1 Foreword............................................................................................................................................3 Acknowledgments....................................................................................................................3 Introduction........................................................................................................................................4 The Benefits of Linux...............................................................................................................4 Who Should Buy This Book.....................................................................................................5 About the Second Edition........................................................................................................5 How This Book Is Organized...................................................................................................6 Chapter 1: The Basics of System Administration...............................................................6 Chapter 2: Installing Linux..................................................................................................6 Chapter 3: Startup and Shutdown......................................................................................6 Chapter 4: Tools of the Trade............................................................................................7 Chapter 5: Creating and Maintaining User Accounts.........................................................7 Chapter 6: Filesystems and Disk Management.................................................................7 Chapter 7: Linux Files and Processes...............................................................................7 Chapter 8: Software Administration...................................................................................7 Chapter 9: Backup and Restore.........................................................................................7 Chapter 10: Printers and the Spooling Subsystem............................................................7 Chapter 11: Serial Communications, Terminals, and Modems..........................................7 Chapter 12: TCP/IP Linux Networking...............................................................................8 Chapter 13: The X Window System...................................................................................8 Chapter 14: Setting Up Your Mail Server...........................................................................8 Chapter 15: Security..........................................................................................................8 Chapter 16: Performance Tuning.......................................................................................8 Chapter 17: Making Your Job Easier with Scripts..............................................................8 Chapter 18: Troubleshooting Your Linux System..............................................................8 Conventions Used in This Book...............................................................................................9 Help Us Help You..................................................................................................................10 Part I: The Basics.............................................................................................................................11 Chapter List............................................................................................................................11 Featuring................................................................................................................................11 Chapter 1: The Basics of System Administration........................................................................12 Overview................................................................................................................................12 Your Role as a System Administrator....................................................................................12 Tasks of a System Administrator...........................................................................................13 Configuring Hardware......................................................................................................13 Installing the Operating System.......................................................................................14 Installing Application Software.........................................................................................14 System Security...............................................................................................................14 Configuring the Kernel.....................................................................................................14 Creating Users and Groups.............................................................................................15 Software Updates.............................................................................................................15 Performance Tuning.........................................................................................................15 Disaster Recovery............................................................................................................15 Capacity Planning............................................................................................................16 Network Administration....................................................................................................16 i Table of Contents Chapter 1: The Basics of System Administration "When You Have a Minute..."...........................................................................................16 Tools of the Linux Administrator............................................................................................16 Commands.......................................................................................................................17 System Logbook..............................................................................................................18 Communicating with Users..............................................................................................20 Working on the System as Root............................................................................................21 Becoming the Root User..................................................................................................21 In Sum....................................................................................................................................23 Chapter 2: Installing Linux..............................................................................................................24 Overview................................................................................................................................24 Benchmarks...........................................................................................................................24 Selecting Hardware................................................................................................................25 Minimal Acceptable Hardware.........................................................................................25 CPU Performance............................................................................................................25 Random Access Memory.................................................................................................26 Selecting Hardware by Intended Usage...........................................................................27 Specialized Hardware Performance Solutions.................................................................28 Types of Hardware to Avoid.............................................................................................33 Selecting a Linux Distribution.................................................................................................35 Red Hat Linux..................................................................................................................35 Mandrake.........................................................................................................................37 Caldera.............................................................................................................................37 SuSE Linux......................................................................................................................38 Slackware Linux...............................................................................................................38 Debian..............................................................................................................................39 The Choice Is Yours.........................................................................................................39 Installing Red Hat Linux.........................................................................................................40 Preparing for Installation..................................................................................................40 Choosing a Partitioning Scheme......................................................................................41 Installing a Server............................................................................................................42 Installing a Workstation....................................................................................................50 Tying Up Loose Ends.......................................................................................................51 In Sum....................................................................................................................................51 Chapter 3: Startup and Shutdown..................................................................................................52 Overview................................................................................................................................52 The Linux Boot Process.........................................................................................................52 The Master Boot Record..................................................................................................53 Boot Loaders..........................................................................................................................55 GRUB: Definition and Configuration................................................................................55 LILO: Definition and Configuration...................................................................................57 Creating a Boot Floppy..........................................................................................................60 Creating a LILO Boot Floppy............................................................................................60 Creating a Boot Floppy without a Boot Loader................................................................61 Using LOADLIN.....................................................................................................................61 Single−User Mode.................................................................................................................62 Initialization and Startup Scripts.............................................................................................63 The Red Hat Model..........................................................................................................63 ii Table of Contents Chapter 3: Startup and Shutdown The Debian Model............................................................................................................67 User Initialization Files...........................................................................................................70 Modifying the Startup Procedure......................................................................................71 Startup Log Files..............................................................................................................75 Shutdown...............................................................................................................................76 Warning Users.................................................................................................................76 Shutdown Log Files..........................................................................................................76 In Sum....................................................................................................................................77 Chapter 4: Tools of the Trade.........................................................................................................78 Overview................................................................................................................................78 Locating Help Resources.......................................................................................................78 Man Pages.......................................................................................................................79 Info Pages........................................................................................................................81 Technical Support..................................................................................................................83 Configuration Support......................................................................................................83 Tailored Linux Development............................................................................................84 General Web Support......................................................................................................84 Webmin..................................................................................................................................85 Command−Line Tools............................................................................................................85 The Bash Shell.................................................................................................................86 Basic Commands.............................................................................................................91 In Sum..................................................................................................................................109 Part II: Managing Users, Processes, and Files...........................................................................110 Chapter List..........................................................................................................................110 Featuring..............................................................................................................................110 Chapter 5: Creating and Maintaining User Accounts.................................................................111 Overview..............................................................................................................................111 User Accounts......................................................................................................................111 The /etc/passwd File......................................................................................................112 Shadowed Passwords....................................................................................................113 Adding New Users.........................................................................................................116 Modifying User Accounts...............................................................................................118 Disabling User Accounts................................................................................................121 Deleting User Accounts..................................................................................................122 Groups.................................................................................................................................123 The Function of Groups.................................................................................................124 The /etc/group File.........................................................................................................124 Adding New Groups.......................................................................................................126 Modifying Groups...........................................................................................................128 Deleting Groups.............................................................................................................129 In Sum..................................................................................................................................130 Chapter 6: Filesystems and Disk Management..........................................................................131 Overview..............................................................................................................................131 Linux Filesystem Support.....................................................................................................131 Locating Filesystems......................................................................................................131 iii Table of Contents Chapter 6: Filesystems and Disk Management Linux Native Filesystems...............................................................................................133 Foreign Filesystems.......................................................................................................137 Network Filesystems......................................................................................................140 Filesystem Design................................................................................................................141 The Physical Structure...................................................................................................141 Inodes and Directories...................................................................................................141 Accessing Filesystems.........................................................................................................142 Mounting and Unmounting Filesystems.........................................................................142 Using Removable Media................................................................................................149 Using Swap Space.........................................................................................................153 Updating and Maintaining Filesystems................................................................................154 Disk Partitioning.............................................................................................................154 Creating a Filesystem....................................................................................................158 Adding a Disk.................................................................................................................159 Replacing a Disk............................................................................................................160 Checking Filesystem Integrity........................................................................................161 In Sum..................................................................................................................................162 Chapter 7: Linux Files and Processes.........................................................................................163 Overview..............................................................................................................................163 The Filesystem Hierarchy Standard.....................................................................................163 Directory Layout.............................................................................................................165 File Characteristics..............................................................................................................167 Determining a Linux File's Type.....................................................................................168 File Types Defined.........................................................................................................170 Processes............................................................................................................................174 The Concept of Multitasking...........................................................................................174 Types of Processes........................................................................................................175 Parent Processes and Their Children............................................................................178 The init Process.............................................................................................................179 Managing Processes......................................................................................................180 Terminating/Restarting with the kill Command...............................................................182 Terminating/Restarting Processes Using Scripts...........................................................183 In Sum..................................................................................................................................184 Chapter 8: Software Administration............................................................................................185 Overview..............................................................................................................................185 Installing Binary Packages...................................................................................................185 Installing an RPM...........................................................................................................185 Installing a Debian Package...........................................................................................189 Installing a Tarball..........................................................................................................190 Compiling Source Code.......................................................................................................191 Compiling from Packages..............................................................................................191 Compiling Tarballs.........................................................................................................192 Kernel Compilation...............................................................................................................194 Why Compile Your Kernel?............................................................................................194 Obtaining a Kernel.........................................................................................................195 Kernel Configuration Options.........................................................................................195 Compiling the Kernel......................................................................................................199 iv Table of Contents Chapter 8: Software Administration Installing the Kernel and Modules..................................................................................200 Testing Your New Kernel...............................................................................................201 Checking for OS Updates....................................................................................................202 The Importance of OS Updates.....................................................................................202 Locating Updates for Your Distribution..........................................................................203 Update Utilities...............................................................................................................205 In Sum..................................................................................................................................206 Chapter 9: Backup and Restore...................................................................................................207 Overview..............................................................................................................................207 Backup Strategies................................................................................................................207 Combining Full and Incremental Backups......................................................................207 Including Differential Backups........................................................................................208 Data−Specific Backups..................................................................................................209 Backup Media......................................................................................................................209 Tapes.............................................................................................................................210 CD−R and CD−RW........................................................................................................215 Other Alternatives..........................................................................................................216 Media Storage................................................................................................................217 Backup Commands and Utilities....................................................................................217 CD−R and CD−RW Backup Tools.................................................................................219 Linux Backup and Restore Tools.........................................................................................224 dump..............................................................................................................................224 restore............................................................................................................................227 tar...................................................................................................................................228 cpio................................................................................................................................233 afio.................................................................................................................................234 Third−Party Tools...........................................................................................................236 Tips while Restoring.......................................................................................................238 Backing Up the Operating System.......................................................................................239 Minimal Backups............................................................................................................239 Complete Backups.........................................................................................................240 Disaster Recovery Techniques............................................................................................240 Single−User Mode.........................................................................................................241 Using a Boot Floppy.......................................................................................................241 Rescue Mode.................................................................................................................242 Third−Party Recovery Software.....................................................................................244 In Sum..................................................................................................................................244 Part III: Communications and Networking..................................................................................246 Chapter List..........................................................................................................................246 Featuring..............................................................................................................................246 Chapter 10: Printers and the Spooling Subsystem....................................................................247 Overview..............................................................................................................................247 Printer Basics.......................................................................................................................247 Types of Printers............................................................................................................247 Printer Interfaces............................................................................................................250 The Linux Printing Process..................................................................................................252 v Table of Contents Chapter 10: Printers and the Spooling Subsystem Tools of the Printing Trade.............................................................................................252 The LPRng Print Spooler...............................................................................................254 Alternative Printing Utilities............................................................................................258 Configuring Printers Using Red Hat's Printconf...................................................................259 Configuring Printers in Webmin...........................................................................................262 Printing with Other Distributions...........................................................................................262 Debian............................................................................................................................262 SuSE..............................................................................................................................262 Slackware.......................................................................................................................263 Kernel Support.....................................................................................................................263 Parallel−Port Printers.....................................................................................................263 RS−232 Serial Devices..................................................................................................265 USB Devices..................................................................................................................265 Remote Printing.............................................................................................................265 In Sum..................................................................................................................................268 Chapter 11: Serial Communications, Terminals, and Modems.................................................269 Overview..............................................................................................................................269 Understanding Serial Devices..............................................................................................269 Standard Serial Devices.................................................................................................269 Unusual Serial Devices..................................................................................................274 Configuring Terminals..........................................................................................................275 Understanding Terminals...............................................................................................275 Configuring a getty Program..........................................................................................276 Using a Serial−Port Console..........................................................................................278 Configuring Modems............................................................................................................279 Dial−out Modem Uses....................................................................................................279 Dial−in Modem Uses......................................................................................................288 Configuring Serial Printers...................................................................................................291 Special Considerations for Serial Printers......................................................................292 When to Use a Serial Printer..........................................................................................292 In Sum..................................................................................................................................292 Chapter 12: TCP/IP Linux Networking.........................................................................................294 Overview..............................................................................................................................294 Understanding TCP/IP Networking......................................................................................294 Network Stacks..............................................................................................................294 Network Addresses........................................................................................................296 Ports...............................................................................................................................298 TCP/IP Configuration...........................................................................................................299 Configuring Network Hardware......................................................................................299 Using DHCP for Configuration.......................................................................................300 Manually Configuring TCP/IP.........................................................................................302 Testing the Setup...........................................................................................................306 File Sharing..........................................................................................................................307 Sharing with Unix or Linux: NFS....................................................................................307 Sharing with Windows: Samba......................................................................................310 Internet Servers...................................................................................................................316 Available Servers...........................................................................................................316 vi Table of Contents Chapter 12: TCP/IP Linux Networking Using a Super Server.....................................................................................................318 In Sum..................................................................................................................................321 Chapter 13: The X Window System..............................................................................................323 Overview..............................................................................................................................323 X Concepts..........................................................................................................................323 X as a Network Protoco.l................................................................................................323 X Security.......................................................................................................................325 X Virtual Consoles..........................................................................................................327 Configuring an X Server.......................................................................................................328 XFree86 4.x....................................................................................................................328 XFree86 3.3.x.................................................................................................................330 Using an X Configuration Tool.......................................................................................331 Starting X Automatically.................................................................................................333 Configuring a Font Server....................................................................................................334 Adding Fonts to a Font Server.......................................................................................334 Configuring a New Font Server......................................................................................336 Unusual Font Servers....................................................................................................337 Building a User Interface atop X..........................................................................................338 Window Managers.........................................................................................................338 Widget Sets....................................................................................................................341 Desktop Environments...................................................................................................341 X Applications................................................................................................................343 In Sum..................................................................................................................................344 Chapter 14: Setting Up Your Mail Server.....................................................................................345 Overview..............................................................................................................................345 Understanding E−Mail Protocols..........................................................................................345 Push and Pull Protocols.................................................................................................345 SMTP.............................................................................................................................347 POP...............................................................................................................................348 IMAP..............................................................................................................................349 Configuring Sendmai.l..........................................................................................................351 Configuring Domains......................................................................................................351 Sendmail Configuration Files and Procedures...............................................................352 Address Masquerading..................................................................................................353 Configuring Relays.........................................................................................................354 Receiving Mail................................................................................................................357 Configuring POP and IMAP.................................................................................................358 Running POP and IMAP Daemons................................................................................358 Setting Up Mail−Only Accounts.....................................................................................359 Using Fetchmail to Acquire Mail from an ISP.................................................................360 Anti−Spam Measures..........................................................................................................364 The Problem of Spam....................................................................................................364 Preventing Outgoing Spam............................................................................................364 Stopping Incoming Spam...............................................................................................366 In Sum..................................................................................................................................369 vii Table of Contents Part IV: System Optimization and Improvement.........................................................................370 Chapter List..........................................................................................................................370 Featuring..............................................................................................................................370 Chapter 15: Security......................................................................................................................371 Overview..............................................................................................................................371 Types of Attacks..................................................................................................................372 Trojan Horse..................................................................................................................372 Back Door......................................................................................................................373 Trusted Host...................................................................................................................373 Buffer Overflow..............................................................................................................374 Scanning or Sniffing.......................................................................................................374 Spoofing.........................................................................................................................374 Denial of Service............................................................................................................375 Password Cracking........................................................................................................375 Social Attacks.................................................................................................................376 Physical Attacks.............................................................................................................376 Types of Security.................................................................................................................377 Securing the Authentication Process...................................................................................379 Hashing Passwords.......................................................................................................379 Shadow Passwords........................................................................................................381 Pluggable Authentication Modules (PAM)......................................................................382 File Permissions...................................................................................................................386 Protecting against Network Intrusion...................................................................................387 Firewalls.........................................................................................................................387 TCP Wrappers...............................................................................................................403 xinetd.............................................................................................................................406 Detecting Intrusion.........................................................................................................406 Applications for Detecting Intrusion................................................................................407 In Sum..................................................................................................................................408 Chapter 16: Performance Tuning.................................................................................................409 Overview..............................................................................................................................409 The Elements of Performance.............................................................................................409 Hardware Performance..................................................................................................409 Software Performance...................................................................................................411 Measuring Performance.......................................................................................................411 Finding Bottlenecks..............................................................................................................412 Using top to Find the Bottleneck....................................................................................412 traceroute.......................................................................................................................415 Tuning the System...............................................................................................................416 nice and renice...............................................................................................................416 Virtual Memory Tuning...................................................................................................417 Serial Port Tuning..........................................................................................................418 Filesystem Tuning..........................................................................................................418 Eliminating Unnecessary Processes..............................................................................422 Compiling for Efficiency..................................................................................................423 Tuning the X Window System........................................................................................425 Upgrading............................................................................................................................426 In Sum..................................................................................................................................426 viii Table of Contents Chapter 17: Making Your Job Easier with Scripts......................................................................428 Overview..............................................................................................................................428 Common Scripting Features................................................................................................428 Identifying a Script..........................................................................................................429 Variables........................................................................................................................429 Control Statements........................................................................................................430 Commands.....................................................................................................................430 The Bash Shell Scripting Language.....................................................................................431 Variables........................................................................................................................431 Conditional Expressions.................................................................................................432 Loops.............................................................................................................................434 Other Types of Scripts.........................................................................................................436 Perl Scripts.....................................................................................................................436 Python Scripts................................................................................................................438 awk and sed Scripts.......................................................................................................438 System Initialization Scripts.................................................................................................440 Writing an Initialization Script.........................................................................................440 Tailoring the rc.local Script.............................................................................................445 Using the cron Facility..........................................................................................................447 Running a Script at a Specific Time.....................................................................................449 Commands Often Used in Shell Scripts...............................................................................449 cat..................................................................................................................................450 cut..................................................................................................................................450 echo...............................................................................................................................451 sort.................................................................................................................................451 xargs..............................................................................................................................452 Using Pipes....................................................................................................................453 In Sum..................................................................................................................................453 Chapter 18: Troubleshooting Your Linux System......................................................................454 Overview..............................................................................................................................454 General Troubleshooting Techniques..................................................................................454 Boot Problems.....................................................................................................................456 FDISK Doesn't Recognize GNU/Hurd Partition.............................................................456 Making a New Boot Floppy to Replace a Lost One.......................................................456 GRUB Is Installed but Just Hangs..................................................................................457 LILO Messages and Their Meanings.............................................................................457 Making the System Boot a New Kerne.l.........................................................................458 Hardware Not Detected at Boot.....................................................................................459 Dual−booting with Another OS Like Windows...............................................................460 Can't Remove Boot Loader from the Master Boot Record.............................................461 Kernel Won't Load or Loads Only Partially....................................................................461 Login Problems....................................................................................................................461 Lost Password................................................................................................................461 Login Incorrect after Entering Username.......................................................................462 System Flashes Quick Message and Drops Back to login Prompt................................462 Login incorrect Message Logging in as root..................................................................463 Network Problems................................................................................................................463 Unknown Host Message................................................................................................463 Network Unreachable Message.....................................................................................464 ix

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"Most Indispensable Linux Book"--2001 Linux Journal Readers Choice AwardsAuthoritative Answers to All Your Linux QuestionsYou can rely on the fully updated second edition of Linux System Administration for answers to all your questions about installing, configuring, and administering Linux. Written
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