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

656 Pages·2002·6.98 MB·English

by  Vicki Stanfield

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
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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
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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
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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
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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
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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
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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
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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
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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
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