Linux System Admin- istration

856 Pages·2008·52.65 MB·English

Contents at a Glance
Introduction
I LinuxDeploymentand Installation
1 IssuesinLinuxInstallation 7
2 AutomatedInstallation 21
II GeneralSystemAdministration
3 UserandGroupAdministration 33
4 BootingUpandShuttingDown 53
5 UsingxdmtoCreateanXWindowsApplication
Server 71
6 AuthenticatingUsersandNetworkResources 83
Using
7 SchedulingTasks 103
8 LinuxProcessManagementandDaemons 117
9 InstallingandUsingRAID 143
10 BackUpandRestore 157
Linux
11 BuildingtheLinuxKernel 193
12 CapacityPlanning 213
III NetworkManagement
13 LinuxNetworkConfigurationandTCP/IP 229
System
14 PrinterandFileSharingwithNFSandSamba 267
15 RoutingwithLinux 289
16 LinuxMailServiceswithsendmail 309
17 FaxServers 343
Admin-
IV Securityand Stability
18 GeneralSecurityIssues 387
19 LinuxandFirewalls 399
20 LogManagementandAnalysis 433
istration
V TheInternetand theIntranet
21 UsingLinuxAsanIntranetServer 447
22 DNS 455
23 ApacheandtheWorldWideWeb 481
ArmanDanesh 24 LinuxDatabaseServers 517
25 Dynamic,Data-DrivenWebSites 545
Gautam Das
26 NewsServices 569
Ram Samudrala 27 FTPServers 591
VI Appendixes
A LinuxCommandReference 625
B LinuxHardwareSupport 717
Index 809
201W.103rdStreet
Indianapolis,Indiana46290
ii
Special Edition Using Linux System Associate Publisher
Administration Tracy Dunkelberger
Copyright# 2000byQue Acquisitions Editor
Gretchen Ganser
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Contents iii
Table of Contents Deletingand DisablingUsers 45
Disabling Users 46
DeletingUserAccounts 47
PasswordSecurityandShadow
I Linux Deployment and
Passwords 48
Installation 5
UsingMD5 Encryption 48
Usingthe ShadowPasswordSuite 49
1 Issues in Linux Installation 7
Troubleshooting 50
Installationand theDistributions 8
4 Booting Up and Shutting Down 53
HardwareConcerns 8
BootingUp 54
Linux DeviceNaming 10
LoadingLinux intoMemory 54
Kernel Initialization andHardware
Linux PartitioningSchemes 14
Configuration 56
SwapPartitions 16
Startup ofSpecialKernel
Using fdisk 16
Threads 60
Linux Run Levels 60
2 Automated Installation 21
Running InitializationScriptsin
Issuesin AutomatedInstallation 22 /etc/rc.d Directory 62
Single-User Mode 64
Automated InstallationwithRedHat’s MultiuserOperating Mode 65
Kickstart 22
ShuttingDown 65
TheKickstartConcept 22
Buildinga KickstartConfiguration shutdown 65
File 22 telinit andinit 66
KickstartUsingaBootFloppyDisk 27 halt 66
KickstartUsingaDHCPServer 27 reboot 67
Ctrl+Alt+Del 67
Troubleshooting 29
Troubleshooting 67
HardwareProblems 68
File SystemCorruption 68
II General System Administration 31
NewlyBuiltKernel Won’tBoot 68
Errors inStartup Scripts 69
3 User and Group Administration 33
Usersand Groups inLinux 34 5 Using xdm to Create an X Windows
The /etc/passwd File 34 Application Server 71
The /etc/group File 37
WhatIsanXApplication Server? 72
CreatingUsers 38 UnderstandingtheRelationship
CreatingUsersManually 38 Between Clientand Serverinthe
CreatingUserswith aSystem X WindowsSystem 72
Utility 40
ChangingUserInformation(Name,
DefaultShell,andSo Forth) 42
iv Special EditionUsingLinux SystemAdministration
Using xdm toCreate Linux-BasedLogins TransferingtheNew NIS Mapsfrom
for XWorkstations andTerminals 73 theNewMaster ServertotheOld
CustomizingthexdmLoginPrompt 78 MasterServer 94
ConfiguringaLinuxClienttoObtainIts PushingtheNewMapsfrom theOld
LoginPromptfrom aRemote xdm MasterServerto AllSlaveServers 95
Server 79 RetiringtheOld MasterServer 95
Troubleshooting 80 RemovinganNISSlave Server 95
AnAlternateApproachtoEditing
6 Authenticating Users and Network ypservers 96
Resources 83
MaintainingNIS Maps 96
EditingNIS Maps 96
NetworkAuthentication inUNIXand
Linux 84 SynchronizingNIS Mapsona
Schedule 97
NIS NetworkConfigurations 84 OtherNISPrograms 97
RoutedNetwork 85
Understandingthe NameServer
NIS Maps 86 Switch 98
SettingUpanNIS MasterServer 87 UsefulScripts 99
SettinganNIS DomainName 87 add-rm-ypservers 100
Populating ConfigurationFiles
Troubleshooting 101
for theNIS Maps 88
Running ypinit 88
MakingSureEverything Is 7 Scheduling Tasks 103
Running 88
SchedulingTasksinLinux 104
SettingUpanNIS Client 89
SettingtheNIS DomainName inthe Usingthe crond Daemon 104
/etc/yp.conf File 89 The crontab ConfigurationFile 105
Running ypbind 90 EditingUsers’ crontab Files 107
Editingthe /etc/passwd File 90 ControllingUseof crontab with
cron.allow and cron.deny 108
Adding anNISSlaveServer 91
SettingtheNIS DomainName 91 Usingthe at Daemon 109
Running ypinit 91 TimeFormatsforthe at
Command 110
Moving NISMaster FunctionstoAnother Checkingthe atd
Machine 91 Queue 110
CreatingtheNew MasterServer Asa RemovingaJob fromthe atd Queue
SlaveServer 92 110
Adding theNewMaster Servertothe RestrictingAccessto atwith at.allow
ypservers Database 92 andat.deny 111
Copyingthe /etc Configuration
Files 93 UsefulScripts 111
DeletingTimeStampFilesfrom fschecker 111
/var/yp on theNew Master 94 syscheck 113
Running make withthe NOPUSH=1
Troubleshooting 115
Option 94
Contents v
8 Linux Process Management and DifferentRAIDArchitectures 145
Daemons 117 RAID Implementations 147
Linux Processesand Daemons 118 InstallingandConfiguringRAIDin
Linux 148
UnderstandingProcesses 118 Supported Controllers 148
What HardwareShouldBe Used? 149
PropertiesandAttributesofProcesses 119 Installation 150
Configuringand TestingYour
ProcessPriority 120
Array 152
Features intheEATADMA
ProcessCreation 120
Driver 153
MonitoringProcesseswiththe ps
Troubleshooting 155
Command 121
Upon Bootup,No SCSIHostsAre
ProcessStates 121
Detected 155
Sample ps Output 121
RAID ConfigurationShows UpAs N
DifferentDisks 156
MonitoringProcesseswiththe top
Machine orControllerIsShut Downin
Command 124
the Middleofa Format 156
TheRoleofDaemons 126 SCSI_ABORT_BUSY Errors Produced
DuringInitialFileSystemFormat 156
StoppingProcesseswiththe kill
Command 127 10 Back Up and Restore 157
Linux Signals 129 WhyBackupIsImportant 158
ChangingProcessPriorities 131 Planninga BackupStrategy 158
TrackingSystemLoad andPerformance TapeDrives 159
withvmstat 133 TestingYour TapeDrive 160
The Procs Section 134
The Memory Section 134 WhatBackupSoftwaretoUse 162
The Swap Section 135 Backing Upwith tar 162
The Io Section 135 Using dump and restore 164
The System Section 135 Backing UpwithAmanda 166
TheCPUsection 135
Interpreting vmstat Output 135 DisasterRecovery 184
Restoringthe OperatingSystemtoa
UsefulScripts 137 New Disk 185
chkdaemon 137
chkload 138 Troubleshooting 189
chkswap 139 Amanda IncorrectlyReportsthe Free
Spaceon theHoldingDiskand
Troubleshooting 140 /tmp 189
amdump Reports AllDisksHave
9 Installing and Using RAID 143 Failed 190
amcheck ReportsPermissions
UnderstandingRAID 144 Problems 190
WhyYou ShouldUseRAID 144
Striping 144
vi Special EditionUsingLinux SystemAdministration
Amanda HasProblemsWritingto 12 Capacity Planning 213
Tape 190
Using amstatus 191 Planningfor Growth 214
Reasonsfor CapacityPlanning 215
11 Building the Linux Kernel 193
ServerSizing 215
OverviewoftheKernel 194
EstimatingtheWorkload 216
WhyRebuildtheKernel? 195 UnderstandingPerformance
Measurement 216
Obtaining NewVersionsofthe
Kernel 196 CaseStudy:Practical Tipson Data
CollectionandAnalysis 220
ConfiguringtheKernel 197 UsingMRTGtoSizetheInternet
Connection 221
CompilingtheKernel 199
TestingYourNew Kernel 200
III Network Management 227
TestingtheKernel WithoutUsinga
BootFloppy 201
13 Linux Network Configuration and
InstallingModules 201 TCP/IP 229
Installingthe NewKernel 202 UnderstandingTCP/IPNetworking 230
TheOSIReferenceModel 231
Patchingthe Kernel 203 TCP/IPProtocol Stack 232
CleaningUpAfter Patching 204 IPAddresses 233
Subnetworksand NetworkMasks 235
UnderstandingModules 204 LimitationsofClassfulAddressing 237
ClasslessInter-DomainRouting
Understandingthe
(CIDR) 237
/procFileSystem 205 Routing 239
TuningKernel Parameterswith
/proc 206 ConfiguringLinuxNetworking 240
ConfiguringNetworking RedHat
SymmetricMultiprocessing 207
Linux6.2 240
ManualLinux Network
Troubleshooting 209
Configuration 247
YourKernel Doesn’tCompile 210
ConfiguringMulti-Homed Hosts 252
YourNew Kernel Doesn’tBoot 210
ImplementingMultiple VirtualIP
YourSystemWon’t Boot 210
Addresses 253
YourSystemCan’tFind aCompressed
Kernel ImageFile 211
Troubleshooting 254
YouCannotCompile OtherPrograms
LinuxNetworkTroubleshooting
After aKernel Upgrade 211
Utilities 255
YourKernel IsToo LargeandToo
Slow 212
YouHaveProblemswithYour Parallel
PortorPrinter 212
YouHaveProblemswithYour
CD-ROMDrive 212
Contents vii
14 Printer and File Sharing with NFS and OpenShortestPath FirstRouting
Samba 267 Protocol 300
WhatIs Samba? 268 Troubleshooting 306
Local HostCannotAccessRemote
Getting SambaUpandRunning 268 Host 307
HostConnectionsFail for Certain
The smb.conf File 270 Applications 308
Testingyoursmb.conf File 273 PoorPerformance 308
Hostand RouterSubnetMask
SharingLinux Fileswith Samba 273
Mismatch 308
OSPFRouters NotEstablishing
SharingLinux Printers withSamba 275
Neighbors 308
UsingLinux Asa SambaClient 276
AccessingSharedPrinters with 16 Linux Mail Services with sendmail 309
Samba 278
EmailSystems 310
WhatIs NFS? 280 Physical ComponentsofaMail
Network 310
ConfiguringNFS 281 Software Componentsofa Mail
UserPermissions andNFS 282 System 312
Mailboxes 313
AccessingRemoteSharedDirectorieswith Mail Aliases 314
NFS 283 Mail Addresses 315
ConfiguringlpdforRemotePrinting 283 Usingsendmail 315
ConfiguringaLocalPrinter 284 sendmailfilesand directories 317
AllowingRemotePrinter The sendmail.cf Configuration
Connections 285 File 320
ConfiguringaRemoteClienttoPrintto Configuringsendmailwith m4 329
aLinux PrintServer 285 Addressing SecurityIssueswith
sendmail 331
Troubleshooting 286
sendmailLogs 332
15 Routing with Linux 289 IMAPand POP3Servers 335
BasicRoutingPrinciples 290 Usingprocmail 336
Linux SoftwareforRouting 292 Troubleshooting 337
Kernel Modulesfor Routing 293 Problemswith .forward Files 337
The route Utility 293 Manually ProcessingtheMail
PrepackagedRouting Queue 338
Distributions 295 DeterminingtheVersionof
sendmail 339
Creatinga LAN-to-LANRouterwith Connectionstothe SMTPPortTaking
Linux 296 a LongTime 340
Relaying DeniedErrors 340
DynamicRouting 297
File andDirectory Permissionsfor
TypesofRoutingProtocols 297
sendmailVersion8.9 andHigher 340
RoutingInformationProtocol 298
viii Special EditionUsingLinux SystemAdministration
UsingWildcardMailExchangers for IV Security and Stability 385
YourDomain 341
OtherMailRelayingProblems 341
18 General Security Issues 387
17 Fax Servers 343 Securityina NetworkedWorld 388
PhysicalSecurity 389
WhatAre FaxServers? 344
Usageand SecurityPolicies 389
SystemSecurity 392
Fax SoftwareforLinux 344
NetworkSecurity 393
InternetSecurity 393
HylaFAX 345
Obtaining HylaFAX 345
SecurityTools 393
InstallingHylaFAX 346
ConfiguringHylaFAXServer 349 KeepingSystems Secure 395
TestingHylaFAX 356
MonitorLogEntries 395
Automating DistributionofReceived
ApplySoftwareUpdates 395
Faxes 359 ReacttoSecurityBreaches 396
HylaFAXClient Setup 360
MonitorSourcesofSecurity
SettingUpanEmail-FaxGateway 363
Information 396
HylaFAXTransfer Logs 366
HylaFAXcrond Jobs 367 19 Linux and Firewalls 399
TroubleshootingHylaFAX 367
AnExample ofaClient-Side FirewallsandtheInternet 400
Problem 368
AnExample ofaServer-Side TypesofFirewalls 401
Problem 368 Packet-FilteringFirewalls 401
DebuggingCommunication ProxyServer Firewalls 403
Problems 369 IPMasqueradingProxyServers 403
UsingEfax 371 FirewallsandNetworkArchitecture 404
InstallingEfax 371
ConfiguringEfax 372 SettingUpaLinux Firewall 406
Sending FaxeswithEfax 373 IPPacketFilteringandIPMasquerading
Receiving FaxeswithEfax 374 UsingIPCHAINS 407
SettingUpa FaxPrintServer 375 PuttingIt AllTogether 418
IPPortForwarding 428
Extending EfaxwithQfax 377
InstallingQfax 377 Troubleshooting 429
Sending FaxesbyEmail 382 ipchains-L Freezes 429
ManagingQfax 383 DNSLookupsFail Partofthe
Time 429
TroubleshootingEfaxand Qfax 384 IPMasqueradingDoesNotWork 430
4096MasqueradedTCP andUDP
ConnectionsAreInsufficient 430
Contents ix
20 Log Management and Analysis 431 Troubleshooting 476
Domain NamesMissing theTrailing
LoggingActivityin Linux 432 Dot 476
ForgettingtoIncrementtheSOA Serial
The syslog Daemon 433 Number 477
MakingChanges tothe syslog.conf ForgettingtoSignalnamedAfterMaking
File 436 Changes toZoneData 477
ForgettingReverseDNSRecords 478
LogRotation 436
Invalid GlueRecord 478
The logrotate Utility 437
Lack ofCoordination AmongDNS
Administrators 478
Case Study:UsefulScripts 441
SourceCodefor su-report 442 Misconfigured resolv.conf File 478
SourceCodefor failed-su 442 Outdated root.hints File 479
23 Apache and the World Wide Web 481
V The Internet and the Intranet 445
LinuxAs aWebServerPlatform 482
21 Using Linux As an Intranet Server 447 Apache’sRole Asa LinuxHTTP
Server 482
UnderstandingIntranets 448
Linux Asa WebServer 448 ConfiguringApache 483
Linux Asa DatabaseServer 451 The httpd.conf File 483
Linux Asa NewsServer 452 The srm.conf File 492
Linux Asa MailServer 452 The access.conf File 497
HardwareRequirements 453 ApacheModules 499
22 DNS 455 ManagingApache 501
Starting theServer 501
TheDomain NameSystem 456 StoppingtheServer 502
RestartingtheServer 502
DNSNameResolution 457 Testingthe Server’sStatus and
SettingUpNameServers 458 ConfigurationFiles 502
ResolvingNames 468
DNSMaintenance 472 VirtualHostingwithApache 502
Creating DNSEntriesfor Each
Load BalancingwithDNS 473 Site 503
Creating aDirectoryHierarchy for the
SecuringDNS 474
Sites 504
RestrictingZoneTransfersto
ConfiguringApache toServeEach
DesignatedSlaveServers Only 474
Site 504
RestrictingZoneTransfersfrom
ProvidingBackwardCompatibility 505
SecondaryServers 475
RestrictingQueriestoYour Name MonitoringYourWebSiteThrough the
Server 475 Logs 507
The AccessLog file 507
UsefulScripts 476
The ErrorLog File 510
ManagingLogs 511
x Special EditionUsingLinux SystemAdministration
BasicWebSite Security 512 25 Dynamic, Data-Driven Web Sites 545
SetYourFileandDirectoryPermissions
Correctly 512 UnderstandingDynamic, InteractiveWeb
ConsiderYourUseofServer-Side Sites 546
IncludesCarefully 513 CGI-BINProgramming 546
ConsiderAllowingUsersAccessto ServerAPIProgramming 548
CGI-BINScriptsCarefully 513
ExamineYourCGI-BINScripts 514 SoftwareforConnecting WebSitesto
DoNotAllowUserstoOverrideGlobal Databases 549
Settings 514 PHP 549
DenyDefaultAccess 515 Zope 549
Web+ 550
Troubleshooting 515 ColdFusion 550
InstallingPHP 551
24 Linux Database Servers 517
PHPInstallationConfiguration
Linux Asa DatabaseServer 518 Parameters 552
Creatinga LinuxDatabaseServer 519 AnOverviewofPHPScripting 560
DeterminingYourDatabaseServer’s CreatingaSimpleDynamicWebSite
HardwareRequirements 519 withPHP 562
Obtaining andInstallingMySQL 520
Troubleshooting 565
ConfiguringandTestingMySQL 521
PHPStops WorkingAfter Installing
DatabaseManagement 528 FrontPageExtensionsfor Apache 566
Startingand StoppingtheServer 528 PHPFiles Are DisplayedAsSource
Connectingtothe Server 528 CodebyApache 566
Creatingand DeletingDatabases and PHPFailstoCompile Becauseofa
Tables 529 MissingLibrary 566
InteractingwithDatabases Using PHPFailstoConnect toMyDatabase
SQL 533 Server 567
Backing UpYourDatabases 538
ManagingUsersand Permissions 539 26 News Services 569
Troubleshooting 542 ABriefHistoryofUsenet 570
Receiving the MySQLserverhasgone
away Error 542 NewsGroupHierarchies 570
Receiving the Host<hostname>is
HardwareRequirements 571
blocked Error 542
Receiving the Toomanyconnections InstallingINN2.2.1 571
Error 543
ReceivingtheOutofmemoryErrorWhen GeneralOverviewofINN 572
Executinga SQLCommand 543 ReceivingIncomingNewsFeeds 573
ReceivingtheAccessDeniedError 543 ProcessingOutgoingNewsFeeds 574
ServicingNewsReadersandFacilitating
theReadingandPostingof
Articles 574
ExpiringArticles 574
LoggingAllActivity 574