Nagios: System and Network Monitoring

463 Pages·2005·6.562 MB·English

by  Wolfgang Barth

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Nagios
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Wolfgang Barth
Nagios
System and Network Monitoring
Munich SanFrancisco
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NAGIOS. Copyright(cid:1)c 2006OpenSourcePressGmbH
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LibraryofCongressCataloging-in-PublicationData
Barth, Wolfgang
Nagios : system and network monitoring / Wolfgang Barth.-- 1st ed.
p. cm.
Includes index.
ISBN 1-59327-070-4
1. Computer networks--Management--Automation. I. Title. TK5105.5.B374 2005
004.6--dc22
2005026745
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Contents
Introduction 15
From Source Code to a Running Installation 23
1 Installation 25
1.1 CompilingtheSourceCode . . . . . . . . . . . . . . . . . . . . . . 26
1.2 InstallingandTestingPlugins . . . . . . . . . . . . . . . . . . . . . 30
1.2.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.2.2 Plugintest . . . . . . . . . . . . . . . . . . . . . . . . . . 32
1.3 ConfigurationoftheWebInterface . . . . . . . . . . . . . . . . . 33
1.3.1 SettingUpApache . . . . . . . . . . . . . . . . . . . . . . 33
1.3.2 UserAuthentication . . . . . . . . . . . . . . . . . . . . . 34
2 NagiosConfiguration 37
2.1 TheMainConfigurationFilenagios.cfg . . . . . . . . . . . . . . . 38
2.2 Objects—anOverview . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.3 DefiningtheMachinestoBeMonitored,withhost . . . . . . . . . 44
2.4 GroupingComputersTogetherwithhostgroup . . . . . . . . . . . 46
2.5 DefiningServicestoBeMonitoredwithservice . . . . . . . . . . . 47
2.6 GroupingServicesTogetherwithservicegroup . . . . . . . . . . . 50
2.7 DefiningAddresseesforErrorMessages:contact . . . . . . . . . . 50
2.8 TheMessageRecipient:contactgroup . . . . . . . . . . . . . . . . 52
2.9 WhenNagiosNeedstoDoSomething:thecommandObject . . . 53
2.10 DefiningaTimePeriodwithtimeperiod . . . . . . . . . . . . . . . 54
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2.11 Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.12 ConfigurationAidsforThoseTooLazytoType . . . . . . . . . . . . 56
2.12.1 Definingservicesforseveralcomputers. . . . . . . . . . . 56
2.12.2 Onehostgroupforallcomputers . . . . . . . . . . . . . . 57
2.12.3 Otherconfigurationaids . . . . . . . . . . . . . . . . . . . 57
2.13 CGIConfigurationincgi.cfg . . . . . . . . . . . . . . . . . . . . . 57
2.14 TheResourcesFileresource.cfg . . . . . . . . . . . . . . . . . . . . 59
3 Startup 61
3.1 CheckingtheConfiguration . . . . . . . . . . . . . . . . . . . . . . 61
3.2 GettingMonitoringStarted . . . . . . . . . . . . . . . . . . . . . . 63
3.2.1 Manualstart . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.2.2 Automaticstart. . . . . . . . . . . . . . . . . . . . . . . . 64
3.2.3 Makingconfigurationchangescomeintoeffect . . . . . . 64
3.3 OverviewoftheWebInterface . . . . . . . . . . . . . . . . . . . . 64
In More Detail... 69
4 NagiosBasics 71
4.1 TakingintoAccounttheNetworkTopology . . . . . . . . . . . . . 72
4.2 ForcedHostChecksvs.PeriodicReachabilityTests . . . . . . . . . . 75
4.3 StatesofHostsandServices . . . . . . . . . . . . . . . . . . . . . 75
5 ServiceChecksandHowTheyArePerformed 79
5.1 TestingNetworkServicesDirectly . . . . . . . . . . . . . . . . . . . 81
5.2 RunningPluginsviaSecureShellontheRemoteComputer . . . . 82
5.3 TheNagiosRemotePluginExecutor . . . . . . . . . . . . . . . . . 82
5.4 MonitoringviaSNMP . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.5 TheNagiosServiceCheckAcceptor . . . . . . . . . . . . . . . . . . 84
6 PluginsforNetworkServices 85
6.1 StandardOptions . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6.2 ReachabilityTestwithPing . . . . . . . . . . . . . . . . . . . . . . 88
6.2.1 check_icmpasaservicecheck . . . . . . . . . . . . . . . 90
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6.2.2 check_icmpasahostcheck . . . . . . . . . . . . . . . . . 91
6.3 MonitoringMailServers . . . . . . . . . . . . . . . . . . . . . . . . 92
6.3.1 MonitoringSMTPwithcheck_smtp. . . . . . . . . . . . . 92
6.3.2 POPandIMAP . . . . . . . . . . . . . . . . . . . . . . . . 95
6.4 MonitoringFTPandWebServers . . . . . . . . . . . . . . . . . . . 97
6.4.1 FTPservices . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.4.2 WebservercontrolviaHTTP . . . . . . . . . . . . . . . . . 98
6.4.3 MonitoringWebproxies . . . . . . . . . . . . . . . . . . . 101
6.5 DomainNameServerunderControl . . . . . . . . . . . . . . . . . 105
6.5.1 DNScheckwithnslookup . . . . . . . . . . . . . . . . . . 106
6.5.2 Monitoringthenameserverwithdig . . . . . . . . . . . . 107
6.6 QueryingtheSecureShellServer . . . . . . . . . . . . . . . . . . . 108
6.7 GenericNetworkPlugins . . . . . . . . . . . . . . . . . . . . . . . 110
6.7.1 TestingTCPports . . . . . . . . . . . . . . . . . . . . . . . 110
6.7.2 MonitoringUDPports . . . . . . . . . . . . . . . . . . . . 112
6.8 MonitoringDatabases . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.8.1 PostgreSQL . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.8.2 MySQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.9 MonitoringLDAPDirectoryServices . . . . . . . . . . . . . . . . . 121
6.10 CheckingaDHCPServer. . . . . . . . . . . . . . . . . . . . . . . . 124
6.11 MonitoringUPSwiththeNetworkUPSTools . . . . . . . . . . . . 126
7 TestingLocalResources 133
7.1 FreeHardDriveCapacity . . . . . . . . . . . . . . . . . . . . . . . 134
7.2 UtilizationoftheSwapSpace. . . . . . . . . . . . . . . . . . . . . 136
7.3 TestingtheSystemLoad. . . . . . . . . . . . . . . . . . . . . . . . 137
7.4 MonitoringProcesses . . . . . . . . . . . . . . . . . . . . . . . . . 138
7.5 CheckingLogFiles . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
7.5.1 Thestandardplugincheck_log . . . . . . . . . . . . . . . 142
7.5.2 Themodernvariation:check_logs.pl . . . . . . . . . . . . 143
7.6 KeepingTabsontheNumberofLogged-inUsers . . . . . . . . . . 144
7.7 CheckingtheSystemTime . . . . . . . . . . . . . . . . . . . . . . 145
7.7.1 CheckingthesystemtimeviaNTP. . . . . . . . . . . . . . 145
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7.7.2 Checkingsystemtimewiththetimeprotocol . . . . . . . 146
7.8 RegularlyCheckingtheStatusoftheMailQueue . . . . . . . . . . 147
7.9 KeepinganEyeontheModificationDateofaFile . . . . . . . . . 148
7.10 MonitoringUPSswithapcupsd . . . . . . . . . . . . . . . . . . . . 149
7.11 NagiosMonitorsItself . . . . . . . . . . . . . . . . . . . . . . . . . 150
7.11.1 Runningthepluginmanuallywithascript . . . . . . . . . 151
7.11.2 check_nagiosasatoolforCGIprograms. . . . . . . . . . 152
7.12 HardwareCheckswithLMSensors . . . . . . . . . . . . . . . . . . 152
7.13 TheDummyPluginforTests . . . . . . . . . . . . . . . . . . . . . 154
8 ManipulatingPluginOutput 155
8.1 NegatingPluginResults . . . . . . . . . . . . . . . . . . . . . . . . 155
8.2 InsertingHyperlinkswithurlize . . . . . . . . . . . . . . . . . . . 156
9 ExecutingPluginsviaSSH 157
9.1 Thecheck_by_sshPlugin . . . . . . . . . . . . . . . . . . . . . . . 158
9.2 ConfiguringSSH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
9.2.1 GeneratingSSHkeypairsontheNagiosserver . . . . . . . 160
9.2.2 Settinguptheusernagiosonthetargethost . . . . . . . 161
9.2.3 CheckingtheSSHconnectionandcheck_by_ssh . . . . . 161
9.3 NagiosConfiguration . . . . . . . . . . . . . . . . . . . . . . . . . 162
10 TheNagiosRemotePluginExecutor(NRPE) 165
10.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
10.1.1 Distribution-specificpackages . . . . . . . . . . . . . . . . 166
10.1.2 Installationfromthesourcecode . . . . . . . . . . . . . . 167
10.2 StartingviatheinetDaemon . . . . . . . . . . . . . . . . . . . . . 168
10.2.1 xinetdconfiguration . . . . . . . . . . . . . . . . . . . . . 168
10.2.2 inetdconfiguration . . . . . . . . . . . . . . . . . . . . . 169
10.3 NRPEConfigurationontheComputertoBeMonitored . . . . . . . 170
10.3.1 Passingparametersontolocalplugins . . . . . . . . . . . 171
10.4 NagiosConfiguration . . . . . . . . . . . . . . . . . . . . . . . . . 172
10.4.1 NRPEwithoutpassingparameterson . . . . . . . . . . . . 172
10.4.2 PassingparametersoninNRPE . . . . . . . . . . . . . . . 173
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10.4.3 Optimizingtheconfiguration . . . . . . . . . . . . . . . . 173
10.5 IndirectChecks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
11 CollectingInformationRelevantforMonitoringwithSNMP 177
11.1 IntroductiontoSNMP . . . . . . . . . . . . . . . . . . . . . . . . . 178
11.1.1 TheManagementInformationBase . . . . . . . . . . . . . 179
11.1.2 SNMPprotocolversions . . . . . . . . . . . . . . . . . . . 183
11.2 NET-SNMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
11.2.1 ToolsforSNMPrequests . . . . . . . . . . . . . . . . . . . 184
11.2.2 TheNET-SNMPdaemon . . . . . . . . . . . . . . . . . . . 187
11.3 Nagios’sOwnSNMPPlugins . . . . . . . . . . . . . . . . . . . . . 196
11.3.1 ThegenericSNMPplugincheck_snmp . . . . . . . . . . . 196
11.3.2 Checkingseveralinterfacessimultaneously. . . . . . . . . 201
11.3.3 Testingtheoperatingstatusofindividualinterfaces . . . . 203
11.4 OtherSNMP-basedPlugins . . . . . . . . . . . . . . . . . . . . . . 205
11.4.1 Monitoringharddrive spaceandprocesseswith nagios-
snmp-plugins . . . . . . . . . . . . . . . . . . . . . . . . 205
11.4.2 Observing the load on network interfaces with check-
iftraffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
11.4.3 Themanubulon.compluginsforspecialapplicationpur-
poses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12 TheNagiosNotificationSystem 215
12.1 WhoShouldbeInformedofWhat,When? . . . . . . . . . . . . . . 216
12.2 WhenDoesaMessageOccur? . . . . . . . . . . . . . . . . . . . . 217
12.3 TheMessageFilter . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
12.3.1 Switchingmessagesonandoffsystemwide . . . . . . . . 218
12.3.2 Enabling and suppressing computer and service-related
messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
12.3.3 Person-relatedfilteroptions . . . . . . . . . . . . . . . . . 221
12.3.4 Caseexamples . . . . . . . . . . . . . . . . . . . . . . . . 222
12.4 ExternalNotificationPrograms . . . . . . . . . . . . . . . . . . . . 224
12.4.1 Notificationviae-mail . . . . . . . . . . . . . . . . . . . . 225
12.4.2 NotificationviaSMS . . . . . . . . . . . . . . . . . . . . . 227
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