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Linux Systems Administrators
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*100072*
*100072*
COIT 13146
Systems Administration
(An Introduction to Linux Systems
Administration)
Study Guide
Systems Administration
Edition 2003
Copyright (Study Guide) Central Queensland University, 2003
Developed by staff of the Faculty of Informatics and Comminication.
Produced and printed by the Distance and Flexible Learning Centre
Central Queensland University
Rockhampton, Queensland
Copyright material herin is reproduced under the provision of the Copyright Act 1968.
Material copied with the permission of thecopyright holder has been duely identified
DEVELOPED BY
David Jones, Kieren Jamieson, Damien Clark, Nathaniel
Fitzgerald-Hood and Anthony Ferguson
Chapter .............................................................................................................................................................................19
The Overview................................................................................................................................................................................19
Introduction...................................................................................................................................................................................19
Other Resources ............................................................................................................................................................................19
The Course ....................................................................................................................................................................................20
LAMENT OF A LINUX STUDENT .................................................................................20
THE RATIONALE........................................................................................................21
WHAT YOU WILL LEARN............................................................................................21
WHY NOT WINDOWS?...............................................................................................23
Course Material.............................................................................................................................................................................23
STUDY GUIDE ...........................................................................................................24
THE COURSE WEBSITE..............................................................................................24
Solving Problems ..........................................................................................................................................................................24
Computers in the Real World ........................................................................................................................................................24
WHAT YOU THINK COMPUTERS ARE ..........................................................................24
SOME ALTERNATIVES................................................................................................26
An Overview of Linux...................................................................................................................................................................28
BOOTING...................................................................................................................28
RUNNING ..................................................................................................................29
SHUTTING DOWN.......................................................................................................30
LAYERS.....................................................................................................................30
Conclusions...................................................................................................................................................................................32
Chapter .............................................................................................................................................................................33
The What, Why and How of Sys Admin .......................................................................................................................................33
Introduction...................................................................................................................................................................................33
What Systems Administrators do ..................................................................................................................................................33
WHY WE NEED THEM ................................................................................................34
WHAT THEY DO.........................................................................................................34
Home and the real world ...............................................................................................................................................................37
What Systems Administrators need to know .................................................................................................................................37
Why UNIX? ..................................................................................................................................................................................39
Unix past, present and future.........................................................................................................................................................40
Linux .............................................................................................................................................................................................40
The relationship between Linux and UNIX ...................................................................................................................................41
Some more sys admin theory.........................................................................................................................................................41
Daily operations ............................................................................................................................................................................42
AUTOMATE, AUTOMATE AND AUTOMATE .................................................................42
SYSTEM MONITORING ...............................................................................................42
Hardware and software..................................................................................................................................................................43
EVALUATION ............................................................................................................43
PURCHASE.................................................................................................................44
INSTALLATION ..........................................................................................................44
HARDWARE...............................................................................................................44
DOCUMENTATION .....................................................................................................45
Policy ............................................................................................................................................................................................48
PENALTIES ................................................................................................................48
TYPES OF POLICY......................................................................................................48
CREATING POLICY.....................................................................................................48
Code of ethics................................................................................................................................................................................49
SAGE-AU CODE OF ETHICS......................................................................................49
SAGE-AU CODE OF ETHICS......................................................................................49
People skills ..................................................................................................................................................................................50
COMMUNICATING WITH USERS .................................................................................50
HOW NOT TO COMMUNICATE WITH USERS.................................................................53
Conclusions...................................................................................................................................................................................53
Chapter .............................................................................................................................................................................54
Information Sources and Problem Solving ....................................................................................................................................54
Introduction...................................................................................................................................................................................54
Other resources..............................................................................................................................................................................54
Information sources.......................................................................................................................................................................54
Professional organisations .............................................................................................................................................................55
THE SAGE GROUPS ..................................................................................................55
SAGE-AU...................................................................................................................55
UNIX USER GROUPS.................................................................................................56
THE ACS, ACM AND IEEE......................................................................................56
Books and magazines ....................................................................................................................................................................56
BIBLIOGRAPHIES .......................................................................................................57
O'REILLY BOOKS.......................................................................................................57
MAGAZINES ..............................................................................................................57
Internet resources ..........................................................................................................................................................................57
THE COURSE WEBSITE ...............................................................................................57
HOW TO USE THE INTERNET ......................................................................................58
SOFTWARE ON THE INTERNET ...................................................................................58
DISCUSSION FORUMS ................................................................................................58
JUST THE FAQS ........................................................................................................59
GOOGLE....................................................................................................................60
MAILING LISTS..........................................................................................................60
OTHER DISCUSSION FORUMS .....................................................................................60
INTERNET BASED LINUX RESOURCES ........................................................................62
Problem solving.............................................................................................................................................................................63
GUIDELINES FOR SOLVING PROBLEMS .......................................................................63
EXAMPLES OF SOLVING PROBLEMS ...........................................................................64
Conclusions...................................................................................................................................................................................65
Review questions...........................................................................................................................................................................65
Chapter .............................................................................................................................................................................66
Using UNIX ..................................................................................................................................................................................66
Introduction...................................................................................................................................................................................66
Other resources..............................................................................................................................................................................66
What you need to learn..................................................................................................................................................................66
Introductory UNIX ........................................................................................................................................................................67
WHY DO I NEED TO KNOW THE COMMAND LINE? ......................................................68
HOW DO I LEARN ALL THIS STUFF? ...........................................................................68
UNIX COMMANDS ARE PROGRAMS ..........................................................................69
vi..................................................................................................................................................................................................69
AN INTRODUCTION TO VI...........................................................................................70
UNIX commands...........................................................................................................................................................................72
PHILOSOPHY OF UNIX COMMANDS ..........................................................................72
UNIX COMMAND FORMAT........................................................................................73
A COMMAND FOR EVERYTHING.................................................................................74
Online help ....................................................................................................................................................................................74
USING THE MANUAL PAGES.......................................................................................75
IS THERE A MAN PAGE FOR... .....................................................................................75
MAN PAGE FORMAT.....................................................................................................76
HTML VERSIONS OF MANUAL PAGES ......................................................................76
Some UNIX commands.................................................................................................................................................................76
IDENTIFICATION COMMANDS....................................................................................77
SIMPLE COMMANDS ..................................................................................................78
FILTERS.....................................................................................................................78
Getting more out of filters .............................................................................................................................................................83
Conclusions...................................................................................................................................................................................84
Chapter .............................................................................................................................................................................85
The File Hierarchy.........................................................................................................................................................................85
Introduction...................................................................................................................................................................................85
WHY? .......................................................................................................................85
The important sections ..................................................................................................................................................................86
THE ROOT OF THE PROBLEM......................................................................................86
Homes for users.............................................................................................................................................................................87
EVERY USER NEEDS A HOME... ..................................................................................87
OTHER HOMES?.........................................................................................................87
/usr and /var...........................................................................................................................................................88
AND THE DIFFERENCE IS............................................................................................88
/USR/LOCAL..............................................................................................................89
LIB, INCLUDE AND SRC ..............................................................................................89
/VAR/SPOOL..............................................................................................................90
X-WINDOWS.............................................................................................................90
Bins ...............................................................................................................................................................................................91
WHICH BIN? ..............................................................................................................91
/BIN...........................................................................................................................91
/SBIN .........................................................................................................................91
/USR/BIN....................................................................................................................93
/USR/LOCAL/BIN..........................................................................................................93
Configuration files, logs and other bits!.........................................................................................................................................93
ETC ETC ETC. .............................................................................................................93
LOGS.........................................................................................................................94
/PROC........................................................................................................................94
/DEV .........................................................................................................................94
Conclusion.....................................................................................................................................................................................94
FUTURE STANDARDS .................................................................................................94
Review questions...........................................................................................................................................................................95
Chapter .............................................................................................................................................................................96
Processes and Files........................................................................................................................................................................96
Introduction...................................................................................................................................................................................96
Other resources..............................................................................................................................................................................96
Multiple users................................................................................................................................................................................96
IDENTIFYING USERS ..................................................................................................97
USERS AND GROUPS ..................................................................................................97
NAMES AND NUMBERS ..............................................................................................97
ID ..............................................................................................................................98
Commands and processes..............................................................................................................................................................98
WHERE ARE THE COMMANDS? ..................................................................................98
WHICH ........................................................................................................................98
WHY CAN'T I RUN MY SHELL SCRIPT? .......................................................................99
WHEN IS A COMMAND NOT A COMMAND? .................................................................99
WHY SHELL COMMANDS ARE FASTER THAN OTHER COMMANDS .............................100
Controlling processes .................................................................................................................................................................. 100
VIEWING EXISTING PROCESSES ...............................................................................101
JOB CONTROL..........................................................................................................105
MANIPULATING PROCESSES ....................................................................................106
Process attributes......................................................................................................................................................................... 109
PARENT PROCESSES.................................................................................................109
PROCESS UID AND GID..........................................................................................109
REAL UID AND GID ...............................................................................................109
EFFECTIVE UID AND GID.......................................................................................109
Files............................................................................................................................................................................................. 110
FILE TYPES ..............................................................................................................111
TYPES OF NORMAL FILES.........................................................................................111
FILE ATTRIBUTES ....................................................................................................112
VIEWING FILE ATTRIBUTES .....................................................................................113
File protection ............................................................................................................................................................................. 114
FILE OPERATIONS....................................................................................................114
USERS, GROUPS AND OTHERS..................................................................................115
THREE SETS OF FILE PERMISSIONS ...........................................................................116
SPECIAL PERMISSIONS.............................................................................................116
Effective UID and GID ............................................................................................................................................................... 117
SETUID AND SETGID ................................................................................................118
Numeric permissions................................................................................................................................................................... 118
SYMBOLIC TO NUMERIC ..........................................................................................119
Changing file permissions ........................................................................................................................................................... 120
CHMOD ......................................................................................................................120
CHOWN ......................................................................................................................121
CHGRP ......................................................................................................................121
CHOWN AND CHGRP ....................................................................................................121
DEFAULT PERMISSIONS ...........................................................................................122
File permissions and directories .................................................................................................................................................. 124
FOR EXAMPLE .........................................................................................................124
WHAT HAPPENS IF? .................................................................................................124
Links ........................................................................................................................................................................................... 125
CREATING LINKS.....................................................................................................125
HARD AND SOFT LINKS, THE DIFFERENCES..............................................................127
Searching the file hierarchy......................................................................................................................................................... 128
THE FIND COMMAND...............................................................................................128
Performing commands on many files .......................................................................................................................................... 133
FIND AND -EXEC.....................................................................................................134
FIND AND BACK QUOTES.........................................................................................134
FIND AND XARGS .....................................................................................................135
Conclusion................................................................................................................................................................................... 135
Review questions......................................................................................................................................................................... 136
Chapter ........................................................................................................................................................................... 138
The Shell ..................................................................................................................................................................................... 138
Introduction................................................................................................................................................................................. 138
Executing commands................................................................................................................................................................... 138
DIFFERENT SHELLS .................................................................................................139
STARTING A SHELL..................................................................................................139
Parsing the command line............................................................................................................................................................ 140
The command line....................................................................................................................................................................... 141
ARGUMENTS ...........................................................................................................141
ONE COMMAND TO A LINE.......................................................................................142
COMMANDS IN THE BACKGROUND ..........................................................................142
Filename substitution................................................................................................................................................................... 143
Removing special meaning.......................................................................................................................................................... 144
Input/output redirection ............................................................................................................................................................... 146
HOW IT WORKS .......................................................................................................146
FILE DESCRIPTORS ..................................................................................................146
STANDARD FILE DESCRIPTORS ................................................................................147
CHANGING DIRECTION ............................................................................................147
USING STANDARD I/O .............................................................................................148
FILTERS...................................................................................................................148
I/O REDIRECTION EXAMPLES...................................................................................149
REDIRECTING STANDARD ERROR ............................................................................149
EVALUATING FROM LEFT TO RIGHT.........................................................................150
Everything is a file ...................................................................................................................................................................... 151
TTY...........................................................................................................................151
DEVICE FILES ..........................................................................................................151
REDIRECTING I/O TO DEVICE FILES.........................................................................152
Shell variables ............................................................................................................................................................................. 153
ENVIRONMENT CONTROL ........................................................................................153
THE SET COMMAND..................................................................................................153
Using shell variables.................................................................................................................................................................... 153
ASSIGNING A VALUE ...............................................................................................153
UNINITIALISED VARIABLES .....................................................................................154
RESETTING A VARIABLE..........................................................................................154
THE READONLY COMMAND..........................................................................................154
THE UNSET COMMAND ..............................................................................................154
ARITHMETIC ...........................................................................................................155
THE EXPR COMMAND ................................................................................................155
ALTERNATIVES TO EXPR FOR ARITHMETIC ..............................................................156
Valid variable names ................................................................................................................................................................... 156
{}...........................................................................................................................156
Environment control.................................................................................................................................................................... 156
PS1 AND PS2 ...........................................................................................................157
BASH EXTENSIONS.....................................................................................................157
Variables and sub-shells .............................................................................................................................................................. 158
FOR EXAMPLE .........................................................................................................158
EXPORT......................................................................................................................158
LOCAL VARIABLES..................................................................................................158
Advanced variable substitution.................................................................................................................................................... 159
Brace expansion .......................................................................................................................................................................... 159
Evaluation order .......................................................................................................................................................................... 161
WHY ORDER IS IMPORTANT.....................................................................................161
THE ORDER .............................................................................................................162
The eval command ........................................................................................................................................................... 162
DOING IT TWICE ......................................................................................................162
Conclusion................................................................................................................................................................................... 163
Review questions......................................................................................................................................................................... 163
Chapter ........................................................................................................................................................................... 165
Text Manipulation ....................................................................................................................................................................... 165
Introduction................................................................................................................................................................................. 165
Other resources............................................................................................................................................................................ 165
Regular expressions..................................................................................................................................................................... 165
RES VERSUS FILENAME SUBSTITUTION AND BRACE EXPANSION..............................166
HOW THEY WORK....................................................................................................168
Repetition, repetitionÖ rep-i-titionÖ ......................................................................................................................................... 168
Concatenation and Alternation .................................................................................................................................................... 170
Different commands, different REs............................................................................................................................................. 170
Tagging ....................................................................................................................................................................................... 170
FOR EXAMPLE .........................................................................................................171
ex, ed, sed and vi .............................................................................................................................................................. 171
SO???......................................................................................................................172
WHY USE ED?...........................................................................................................172
ED COMMANDS ........................................................................................................172
FOR EXAMPLE .........................................................................................................174
THE SED COMMAND..................................................................................................175
SED COMMAND FORMAT ...........................................................................................175
Understanding complex commands............................................................................................................................................. 176
Conclusions................................................................................................................................................................................. 177
Review questions......................................................................................................................................................................... 177
Chapter ........................................................................................................................................................................... 178
Shell Programming...................................................................................................................................................................... 178
Introduction................................................................................................................................................................................. 178
SHELL PROGRAMMING - WHY?..............................................................................178
SHELL PROGRAMMING - WHAT? ...........................................................................178
SHELL PROGRAMMING - HOW?..............................................................................179
The basics.................................................................................................................................................................................... 179
A BASIC PROGRAM..................................................................................................179
AN EXPLANATION OF THE PROGRAM .......................................................................180
All you ever wanted to know about variables.............................................................................................................................. 182
WHY? .....................................................................................................................182
PREDEFINED VARIABLES .........................................................................................183
PARAMETERS - SPECIAL SHELL VARIABLES .............................................................184
ONLY NINE PARAMETERS? ......................................................................................185
THE DIFFERENCE BETWEEN $* AND $@ ..................................................................186
The basics of Input/Output (I/O) ................................................................................................................................................. 187
And now for the hard bits............................................................................................................................................................ 189
SCENARIO ...............................................................................................................189
IF ... THEN ... MAYBE? .............................................................................................190
TESTING TESTING....................................................................................................191
EXPRESSIONS, EXPRESSIONS!..................................................................................192
ALL ABOUT CASE.....................................................................................................194
LOOPS AND REPEATED ACTION COMMANDS ............................................................194
WHILE ......................................................................................................................195
FOR..........................................................................................................................195
MODIFYING SCANIT ................................................................................................196
PROBLEMS WITH RUNNING SCANIT..........................................................................196
SO WHAT IS HAPPENING ..........................................................................................198
Speed and shell scripts................................................................................................................................................................. 200
WHAT'S THE MISTAKE.............................................................................................200
SOLUTION IN C........................................................................................................200
SHELL SOLUTION WRITTEN BY C PROGRAMMER .....................................................201
SHELL SOLUTION BY SHELL PROGRAMMER .............................................................201
COMPARING THE SOLUTIONS...................................................................................201
THE PROBLEM .........................................................................................................202
A SOLUTION FOR SCANIT?.......................................................................................202
NUMBER OF PROCESSES ..........................................................................................202
until......................................................................................................................................................................................... 203
BREAK AND CONTINUE ..............................................................................................203
REDIRECTION..........................................................................................................204
Now for the really hard bits......................................................................................................................................................... 205
FUNCTIONAL FUNCTIONS ........................................................................................205
LOCAL ......................................................................................................................206
THE RETURN TRIP .....................................................................................................206
Difficult and not compulsory....................................................................................................................................................... 207
RECURSION: (SEE "RECURSION") ............................................................................207
WAIT'ING AND TRAP'ING ...........................................................................................208
Bugs and Debugging ................................................................................................................................................................... 212
METHOD 1 - SET .....................................................................................................212
METHOD 2 ñ ECHO...................................................................................................212
SOME EXAMPLES OF SOME VERY COMMON MISTAKES ..........................................212
And now for the really, really hard bits ....................................................................................................................................... 213
WRITING GOOD SHELL PROGRAMS ..........................................................................213
EVAL THE WONDERFUL!...........................................................................................214
Step-by-step................................................................................................................................................................................. 217
THE PROBLEM .........................................................................................................217
SOLVING THE PROBLEM ..........................................................................................218
THE FINAL PROGRAM - A LISTING............................................................................226
Conclusions................................................................................................................................................................................. 229
Review questions......................................................................................................................................................................... 229
References................................................................................................................................................................................... 230
Chapter ............................................................................................................................................................... 231
Users ........................................................................................................................................................................................... 231
Introduction................................................................................................................................................................................. 231
Other resources............................................................................................................................................................................ 231
What is a UNIX account?............................................................................................................................................................ 231
LOGIN NAMES .........................................................................................................232
PASSWORDS ............................................................................................................233
THE UID.................................................................................................................233
HOME DIRECTORIES ................................................................................................234
LOGIN SHELL...........................................................................................................234
DOT FILES ...............................................................................................................234
SKELETON DIRECTORIES .........................................................................................236
THE MAIL FILE ........................................................................................................236
MAIL ALIASES.........................................................................................................236
Account configuration files ......................................................................................................................................................... 238
Everyone can read /etc/passwd ............................................................................................................................................ 239
THIS IS A PROBLEM..................................................................................................239
PASSWORD MATCHING ............................................................................................239
THE SOLUTION ........................................................................................................239
SHADOW FILE FORMAT............................................................................................240
Groups......................................................................................................................................................................................... 240
SHADOW PASSWORDS FOR GROUPS ........................................................................240
LIMITING USERS ACCESS BY GROUPS.......................................................................241
THE DEFAULT GROUP ..............................................................................................241
OTHER GROUPS .......................................................................................................241
USER PRIVATE GROUPS ...........................................................................................241
Special accounts .......................................................................................................................................................................... 242
RESTRICTED ACTIONS .............................................................................................242
BE CAREFUL............................................................................................................242
The mechanics............................................................................................................................................................................. 243
OTHER CONSIDERATIONS ........................................................................................243
PRE-REQUISITE INFORMATION ................................................................................243
ADDING AN /ETC/PASSWD ENTRY ...........................................................................244
THE INITIAL PASSWORD ..........................................................................................244
/ETC/GROUP ENTRY ................................................................................................244
THE HOME DIRECTORY............................................................................................245
THE STARTUP FILES.................................................................................................245
ONE COMMAND TO RULE THEM ALL........................................................................245
SETTING UP MAIL ....................................................................................................246
TESTING AN ACCOUNT ............................................................................................247
INFORM THE USER ...................................................................................................248
Removing an account .................................................................................................................................................................. 249
DISABLING AN ACCOUNT ........................................................................................249
The Goals of Account Creation ................................................................................................................................................... 250
Making it simple.......................................................................................................................................................................... 250
USERADD ..................................................................................................................250
USERDEL AND USERMOD ............................................................................................250
GRAPHICAL TOOLS..................................................................................................250
Automation.................................................................................................................................................................................. 251
GATHERING THE INFORMATION...............................................................................251
POLICY....................................................................................................................251
CREATING THE ACCOUNTS ......................................................................................251
ADDITIONAL STEPS .................................................................................................252
CHANGING PASSWORDS WITHOUT INTERACTION.....................................................252
Delegation ................................................................................................................................................................................... 252
Allocating root privilege.............................................................................................................................................................. 252
SUDO ADVANTAGES ................................................................................................254
Conclusions................................................................................................................................................................................. 255
Review questions......................................................................................................................................................................... 255
References................................................................................................................................................................................... 256
Chapter ............................................................................................................................................................... 257
Managing File Systems ............................................................................................................................................................... 257
Introduction................................................................................................................................................................................. 257
WHAT? ...................................................................................................................257
WHY? .....................................................................................................................257
Other resources............................................................................................................................................................................ 258
A scenario.................................................................................................................................................................................... 258
Devices - Gateways to the kernel ................................................................................................................................................ 258
A DEVICE IS... .........................................................................................................258
DEVICE FILES ARE...................................................................................................259
DEVICE DRIVERS ARE..............................................................................................259
/DEV .......................................................................................................................259
PHYSICAL CHARACTERISTICS OF DEVICE FILES .......................................................260
MAJOR AND MINOR DEVICE NUMBERS ARE... ..........................................................261
FINDING THE DEVICES ON YOUR SYSTEM.................................................................261
WHY USE DEVICE FILES? .........................................................................................263
CREATING DEVICE FILES .........................................................................................264
THE USE AND ABUSE OF DEVICE FILES.....................................................................265
Devices, Partitions and File systems............................................................................................................................................ 266
DEVICE FILES AND PARTITIONS ...............................................................................266
PARTITIONS AND FILE SYSTEMS ..............................................................................267
PARTITIONS AND BLOCKS .......................................................................................268
USING THE PARTITIONS ...........................................................................................268
THE VIRTUAL FILE SYSTEM....................................................................................269
DIVIDING UP THE FILE HIERARCHY - WHY? .............................................................269
SCENARIO UPDATE .................................................................................................271
The Linux Native File System - ext3 ........................................................................................................................................ 272
OVERVIEW ..............................................................................................................272
I-NODES..................................................................................................................273
PHYSICAL STRUCTURE AND FEATURES ...................................................................274
Journaling.................................................................................................................................................................................... 275
ADVANTAGES OF JOURNALING................................................................................275
TYPES OF JOURNALING............................................................................................276
HOW DOES JOURNALING WORK? .............................................................................276
Creating file systems ................................................................................................................................................................... 278
MKFS........................................................................................................................278
SCENARIO UPDATE .................................................................................................279
LOGICAL VOLUME MANAGEMENT..........................................................................280
Mounting & UN-mounting Partitions & Devices ........................................................................................................................ 281
MOUNT ......................................................................................................................281
UMOUNT ....................................................................................................................282
MOUNTING WITH THE /ETC/FSTAB FILE .................................................................283
SCENARIO UPDATE .................................................................................................284
File Operations ............................................................................................................................................................................ 285
CREATING A FILE ....................................................................................................285
LINKING FILES.........................................................................................................285
LN............................................................................................................................286
Checking the file system.............................................................................................................................................................. 287
WHY ME? ...............................................................................................................287
WHAT TO DO...........................................................................................................288
FSCK........................................................................................................................288
USING FSCK.............................................................................................................288
WHAT CAUSED THE PROBLEM? ...............................................................................289
Conclusions................................................................................................................................................................................. 289
Review questions......................................................................................................................................................................... 289
References................................................................................................................................................................................... 291
Chapter ............................................................................................................................................................... 292
Backups....................................................................................................................................................................................... 292
Introduction................................................................................................................................................................................. 292
Other resources............................................................................................................................................................................ 292
Backups aren't enough................................................................................................................................................................. 293
Characteristics of a good backup strategy.................................................................................................................................... 293
EASE OF USE ...........................................................................................................293
TIME EFFICIENCY ....................................................................................................293
EASE OF RESTORING FILES ......................................................................................294
ABILITY TO VERIFY BACKUPS..................................................................................294
TOLERANCE OF FAULTY MEDIA...............................................................................294
PORTABILITY TO A RANGE OF PLATFORMS ..............................................................295
Considerations for a backup strategy........................................................................................................................................... 295
The components of backups ........................................................................................................................................................ 295
SCHEDULER ............................................................................................................296
TRANSPORT.............................................................................................................296
MEDIA ....................................................................................................................298
Commands................................................................................................................................................................................... 298
DUMP AND RESTORE ..................................................................................................299
DUMP ON LINUX .......................................................................................................299
THE RESTORE COMMAND .........................................................................................300
Using dump and restore without a tape ................................................................................................................................. 301
OUR PRACTICE FILE SYSTEM ...................................................................................301
DOING A LEVEL 0 DUMP..........................................................................................301
RESTORING THE BACKUP.........................................................................................302
ALTERNATIVE.........................................................................................................302
THE TAR COMMAND.................................................................................................303
THE DD COMMAND...................................................................................................304
THE MT COMMAND...................................................................................................305
Compression programs................................................................................................................................................................ 306
COMPRESS ................................................................................................................307
GZIP........................................................................................................................307
Conclusions................................................................................................................................................................................. 307
Review questions......................................................................................................................................................................... 308
Chapter ............................................................................................................................................................... 309
Startup and Shutdown.................................................................................................................................................................. 309
Introduction................................................................................................................................................................................. 309
Other resources............................................................................................................................................................................ 309
A booting overview ..................................................................................................................................................................... 309
Finding the kernel........................................................................................................................................................................ 310
ROM ......................................................................................................................310
THE BOOTSTRAP PROGRAM .....................................................................................310
Booting on a PC .......................................................................................................................................................................... 311
ON THE FLOPPY.......................................................................................................311
MAKING A BOOT DISK .............................................................................................311
USING A BOOT LOADER ...........................................................................................312
Starting the kernel ....................................................................................................................................................................... 313
KERNEL BOOT MESSAGES........................................................................................313
Starting the processes .................................................................................................................................................................. 315
RUN LEVELS............................................................................................................316
/ETC/INITTAB........................................................................................................316
System configuration................................................................................................................................................................... 319
Terminal logins ........................................................................................................................................................................... 320
Startup scripts.............................................................................................................................................................................. 320
THE LINUX PROCESS ...............................................................................................321
/etc/rc.d/init.d .....................................................................................322
Why won't it boot? ...................................................................................................................................................................... 322
SOLUTIONS .............................................................................................................323
MAKING A BOOT DISK .............................................................................................323
USING RESCUE MODE ON THE CD-ROM .................................................................324
USING THE ALTERNATIVE BOOT ..............................................................................325
DISASTER RECOVERY SOLUTIONS............................................................................326
Solutions to hardware problems .................................................................................................................................................. 327
DAMAGED FILE SYSTEMS ........................................................................................327
IMPROPERLY CONFIGURED KERNELS .......................................................................327
Shutting down ............................................................................................................................................................................. 328
REASONS FOR SHUTTING DOWN ..............................................................................328
BEING NICE TO THE USERS.......................................................................................329
Commands to shutdown........................................................................................................................................................... 329
SHUTDOWN ..................................................................................................................330
WHAT HAPPENS ......................................................................................................330
THE OTHER COMMANDS ..........................................................................................331
Conclusions................................................................................................................................................................................. 331
Review questions......................................................................................................................................................................... 331
References................................................................................................................................................................................... 332
Chapter ............................................................................................................................................................... 333
Kernel.......................................................................................................................................................................................... 333
The heart that keeps the system pumping .................................................................................................................................... 333
Other resources............................................................................................................................................................................ 333
Why the kernel? .......................................................................................................................................................................... 334
How? ........................................................................................................................................................................................... 335
The lifeless image........................................................................................................................................................................ 335
Inside the great unknown, the kernel ........................................................................................................................................... 336
Documentation ............................................................................................................................................................................ 339
The first incision.......................................................................................................................................................................... 339
MAKING THE HEART BEAT... ...................................................................................339
The proc file system.................................................................................................................................................................. 340
Really, why bother?..................................................................................................................................................................... 342
COMPILING THE SOURCE .........................................................................................343
STANDARD UNIX COMPILATION .....................................................................................343
DEPENDENCIES .......................................................................................................348
COMPILATION .........................................................................................................348
CONFIGURING THE BOOT LOADER ...........................................................................349
Kernel Modules ........................................................................................................................................................................... 350
KERNEL MODULE UTILITIES ...................................................................................351
KMOD: THE KERNEL MODULE LOADER......................................................................353
Installing pre-compiled kernels using RPM................................................................................................................................. 353
APPLYING PATCHES ................................................................................................354
THATíS ALL GREAT, BUT HOW LONG IS IT GOING TO TAKE? ....................................355
COMMON PROBLEMS...............................................................................................356
Conclusions................................................................................................................................................................................. 357
Review questions......................................................................................................................................................................... 357
References................................................................................................................................................................................... 358
Chapter ............................................................................................................................................................... 359
Automation and Observation....................................................................................................................................................... 359
Introduction................................................................................................................................................................................. 359
Other resources............................................................................................................................................................................ 359
Automation and cron................................................................................................................................................................. 359
COMPONENTS OF CRON .............................................................................................360
CRONTAB FORMAT ......................................................................................................360
CREATING CRONTAB FILES..........................................................................................361
Current Observation .................................................................................................................................................................... 362
DF ............................................................................................................................362
DU ............................................................................................................................362
SYSTEM STATUS .....................................................................................................363
THE NICE VALUE.....................................................................................................365