Nagios Module 1

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GnuGroup InternationalGnuGrou

p International

NagiosN

agios

IT infrastructure monitoring toolIT infrastructure monitorin

g tool

ILGILGInsight GNU/Linux GroupIns

ight GNU/Linux Group

Reinventing the way you,Reinventing the way you,Think,Think,Learn,Learn,WorkWork


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NAGIOS

MODULE - 1


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Index of module - 1

Introduction

History of Naios

System !e"uirements

#rere"uisites Licensin

Do$nloadin

Ad%ice for &einners

'uic(start installation

Naios Arc)itecture #luins

!emote MonitorinMec)anisms

Monitorin *indo$s

Monitor !emote Linux Host

Monitor Net$or( S$itc)

+onfiuration o%er%ie$

O,ect confiuration o%er%ie$ O,ect Definitions

!unnin Naios

Notifications

Host+)ec(s

Ser%ice +)ec( Acti%e +)ec(

#assi%e +)ec(

States ty.es


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Introduction

What is Nagios Core?

Nagios CoreTM is an Open Source system and network monitoring

application.

It watches hosts and services that you specify, alerting youwhen things go bad and when they get better.

Nagios Core was originally designed to run under Linux,

although it should wor under most other unices as well.


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History of Naios

History +)art

)tt./00$$$naiosor0a,out0)istory
http://www.nagios.org/about/historyhttp://www.nagios.org/about/history


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System !e"uirements

2)e only soft$are re"uirement for runnin Naios+ore is a mac)ine

!unnin Linux 3or UNI4 %ariant5 Has net$or( access A + com.iler installed A $e, ser%er 3.referra,ly A.ac)e5

d li,rary %ersion 167


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#rere"uisites

For Centos / Redhat distro A.ac)e #H# G++ com.iler GD de%elo.ment li,raries

!!!!!!!!!!!!!!!!!!!Yum it !!!!!!!!!!!!!!!!!!!!! yum install )tt.d .). yum install cc li,c li,c-common yum install d d-de%el


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Licensin

Nagios Core is licensed under the ter!s of the

GNU General Public License Version 2

as published by the "ree #oftware "oundation.


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Do$nloadin

)tt./00$$$naiosor0do$nload


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Advice for BeginnersAdvice for Beginners

Relax - its going to take some time....Relax - its going to take some time....

Use the quickstart instructionsUse the quickstart instructions

Read the documentationRead the documentation

Seek the help of othersSeek the help of others


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#rere"uisites

Already Diccussed

Also disa,le selinux

8um u.date

Already Diccussed


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User creation

9 su : l

9 0usr0s,in0useradd -m naios

9 .ass$d naios

Group Creation

15 +reate a ne$ nagcmrou. for allo$in external commands to ,esu,mitted t)rou) t)e $e, interface

;5 Add ,ot) t)e naios user and t)e a.ac)e user to t)e rou.

9 0usr0s,in0rou.add nacmd9 0usr0s,in0usermod -a -G nacmd naios

9 0usr0s,in0usermod -a -G nacmd a.ac)e


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Do$nload Naios and t)e #luins)tt./00$$$naiosor0do$nload

+reate a directory for storin t)e do$nloads

9 m(dir


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Compile and Install NagiosExtract the Nagios source code tarball

9 cd


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Compile and Install Nagios

Run the Nagios conigure script" passing the name o the group #ou createdearlier li$e so%

9 0confiure --&ith'command'group(nagcmd

) ma(e all

Install binaries" init script" sample conig iles and set permissions on theexternal command director#

9 ma(e install

9 ma(e install-init9 ma(e install-confi

9 ma(e install-commandmode

Dont start Nagios yet- theres still more that needs to be done..


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Configure the We! Interface

Install the Nagios &eb conig ile in the *pache cond director#

9 ma(e install-$e,conf

Create a nagiosadmin account or logging into the Nagios &eb interace

Remem!er the passwor#ou assign to this account ' #ou+ll need it later

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart *pache to ma$e the ne& settings ta$e eect

# service httpd restart


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Compile , Install the Nagios -lugins

Extract the Nagios plugins source code tarball

9 cd 11tar=

9 cd naios-.luins-1>11

Compile and install the plugins

9 0confiure --$it)-naios-user?naios --$it)-naios-rou.?naios9 ma(e

9 ma(e install


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.tart Nagios

*dd Nagios to the list o s#stem serices and hae it automaticall# start &hen thes#stem boots

9 c)(confi --add naios9 c)(confi naios on

0eri# the sample Nagios coniguration iles

9 0usr0local0naios0,in0naios -% 0usr0local0naios0etc0naioscf

I there are no errors" start Nagios

9 ser%ice naios start

Add naios ser%ice torunle%els

@erify confifile


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If you see me,

I am configured

And ready


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Naios Arc)itecture*rchitecture

Nagios is built on a serer / agents architecture

Usually on a net$or( a Naios ser%er is runnin on a )ost

and plugins are running on all the remote hosts t)at need to ,e monitored

2)ese .luins send information to t)e ser%er $)ic) dis.lays t)em in a GUI


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Naios Arc)itecture


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#luins *hat *re -lugins1

Naios .luins are stanalone e"tensionsto Naios +ore .ro%ide lo$-le%el intellience on )o$ to monitor an#thing and eer#thing $it)

Naios +ore

#luins operate as standalone applications ,ut are enerally designed to beexecuted b# Nagios Core

#luinsprocess command-line arguments o a,out t)e ,usiness of .erformin as.ecific ty.e of c)ec(

and then return the results to Nagios Core or urther processing

#luins can eit)er ,e compiled binaries 3$ritten in + +BB etc5 or executablescripts 3s)ell #erl #H# etc5

#luins act as an abstraction la#er,et$een t)e monitoring logic.resent in t)eNagios daemonand t)e actual ser%ices and )osts t)at are ,ein monitored

2he upside o this t#pe o plugin architecture%

2)at you can monitor ust a,out anyt)in you can t)in( of

If you can automate t)e .rocess of c)ec(in somet)in you can monitor it $it)

Naios


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#luins


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#luins3hat -lugins *re *ailable1

2)ere are .luins currently a%aila,le to monitor many different (inds of de%ices andser%ices includin/

H22# #O#7 IMA# C2# SSH DH+#

+#U Load Dis( Usae Memory Usae +urrent Users

Unix0Linux *indo$s and Net$are Ser%ers

!outers and S$itc)es etc

0c)ec()tt. :)el.

4ical -lugins can be do&nloaded

Nagios -lugins -ro5ect% http%//nagiosplugsourceorgenet/

Nagios 6o&nloads -age% http%//&&&nagiosorg/do&nload/

NagiosExchangeorg% http%//&&&nagiosexchangeorg/


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!emote Monitorin Mec)anisms

789 chec$:b#:ssh

*dd Nagios to the list o s#stem serices and hae it automaticall# start &hen thes#stem boots

Since you $ant to execute a command

3a c)ec(-commandF or a naios .luin to et t)e state of some .rocess on t)e remote)osts5

2)e o,%ious solution is to run it t)rou) a remote s)ell on t)e taret system -

ss) user)ost FcommandF

e

ss) ilnode7ls -l 0,in

Naios )as a c)ec(,yss) command t)at $or(s in a similar manner

2)is re"uires t)e taret to )a%e an ssh#server running

you need to set u. naios account on t)e remote )ost and arrane for non-interacti%eaut)entication 3e (ey-,ased aut)entication or ,y referin to username and .ass$ordsin a confiuration file5

*ill execute ls -l 0,in+ommand on remote system
mailto:ilg@node03mailto:ilg@node03


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Desin O%er%ie$


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7;9 nrpe

NR-E stands or Nagios Remote $rocess %"ecution%

2)e N!#E addon is desined to allo$ you to execute Naios .luins on remoteLinux/Unix machines

2)e main reason for doin t)is is to allo$ Naios to monitor local resources 3li(e +#U

load memory usae etc5 on remote mac)inesSince t)ese .u,lic resources are not usually ex.osed to external mac)ines an aentli(e N!#E must ,e installed on t)e remote Linux0Unix mac)ines

2)is is a !emote Aent arc)itecture /

An nrpeaent on t)e taret executes t)e re"uested c)ec(-commands and re.orts

,ac( t)e results /Nagios 7< nagios host nrpe9 < nrpe on remote host < command


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Desin O%er%ie$


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7=9 chec$:nt

!emote Aent mec)anism s.ecifically for *indo$s systems +once.tually similar toc)ec(,yss) and c)ec(nr.e

Monitorin .ri%ate ser%ices or attri,utes of a *indo$s mac)ine re"uires t)at you installan aent on it

2)is aent acts as a .roxy ,et$een t)e Naios .luin t)at does t)e monitorin and t)e

actual ser%ice or attri,ute of t)e *indo$s mac)ine

*it)out installin an aent on t)e *indo$s ,ox Naios $ould ,e una,le to monitor.ri%ate ser%ices or attri,utes of t)e *indo$s ,ox

*e $ill ,e installin t)e NS+lientBB addon on t)e *indo$s mac)ine and usin t)ec)ec(nt .luin to communicate $it) t)e NS+lientBB addon

Note/ 2)e c)ec(nt .luin s)ould already ,e installed on t)e Naios ser%er


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Desin O%er%ie$


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7>9 N.C*

N.C* is Nagios .erice Chec$ *cceptor

ItFs an additional daemon on your Naios )ost

Acce.ts and .rocesses c)ec( results su,mitted ,y ot)er Naios )osts or any ot)er.roram t)at manaes to deli%er an NS+A messae t)at says somet)in useful a,out

Ser%ice

#rocess

Soft$are or

Hard$are state on a 3remote5 )ost

As suc) NS+A is instrumental in remote and distri,uted monitorin


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Desin O%er%ie$


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Monitorin *indo$s Mac)ines4erie&

Collo$in t)ree ste.s $ill )a..en on a %ery )i) le%el $)en Naios3installed on t)e naios-ser%er5 monitors a ser%ice 3for e dis( s.aceusae5 on t)e remote *indo$s )ost

Naios $ill execute chec$:nt command on nagios'sererandre"uest it to monitor dis$ usage on remote &indo&s host

2)e chec$:nt on the nagios'serer &ill contact the N.Client??ser%ice on remote $indo$s )ost and re"uest it to execute t)[email protected]*CE on the remote host

2)e results of t)e [email protected]*CE command$ill ,e returned ,ac(,y NS+lientBB daemon to t)e c)ec(nt on naios-ser%er


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Monitorin *indo$s Mac)ines

Follo&ing lo& summariAes the aboe explanation%

Nagios .erer 7chec$:nt9 J:K !emote )ost 3NS+lientBB5 J:[email protected]*CE

Nagios .erer 7chec$:nt9 J: !emote )ost 3NS+lientBB5 J: [email protected]*CE

7returns dis$ space usage9


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II >steps to setup nagios on remote &indo&s host

1 Install NS+lientBB on t)e remote $indo$s ser%er

6o&nload N.C- B=8 7N.Client??'3in=;'B=8msi9 from NS+lientBB #roectNS+lientBB is an open source &indo&s sericet)at allo$s perormance metricsto ,eat)ered ,y Naios for $indo$s ser%ices

Go t)rou) t)e follo$in fi%e NS+lientBB installation ste.s to et t)e installationcom.leted

315 NS+lientBB *elcome Screen

3;5 License Areement Screen

375 Select Installation o.tion and location Use t)e default o.tion and clic( next

3>5 !eady to Install Screen +lic( on Install to et it started

35 Installation com.leted Screen


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7 odi# the N.Cini

315 Modify NS+ini and uncomment dll/ Edit t)e +/#roram CilesNS+lientBBNS+inifile and uncomment eer#thing under PmodulesQ except RemoteConigurationdlland +)ec(*MIdll1

PmodulesQ

R9 NS+LIEN2BB MODULES

R9 A list $it) DLLs to load at startu.

R 8ou $ill need to ena,le some of t)ese for NS+lientBB to $or(

R

R

R N O 2 I + E - 8 O U H A @ E 2 O E D I 2 2 H I S

R

i i i d )i


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R

CileLoerdll

+)ec(Systemdll

+)ec(Dis(dll

NS+lientListenerdllN!#EListenerdll

Sys2raydll

+)ec(E%entLodll

+)ec(Hel.ersdllR+)ec(*MIdll

i i i d )i


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Monitorin *indo$s Mac)inesR

R !emote+onfiuration IS AN E42!EM EA!L8 IDEA SO DON2 USE CO!#!ODU+2ION EN@I!OMNEM2S

R!emote+onfiurationdll

R NS+A Aent is a ne$ ,eta module use $it) care

NS+AAentdll

R LUA scri.t module used to $rite your o$n c)ec( deamon 3sort of5 early ,eta

LUAScri.tdll

R Scri.t to c)ec( external scri.ts and0or internal aliases early ,eta

+)ec(ExternalScri.tsdll

R +)ec( ot)er )osts t)rou) N!#E extreme ,eta and .ro,a,ly a ,it danerous /5

N!#E+lientdll


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375 odi# N.Cini and uncomment port Edit t)e +/#roramCilesNS+lientBBNS+ini file and uncomment t)e .ort9 underPNS+lientQ section

R9 NS+LIEN2 #O!2 NUM&E!

R 2)is is t)e .ort t)e NS+lientListenerdll $ill listen to

port(8;>D


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>9 odi# N.Cini and speci# pass&ord 8ou can also s.ecify a.ass$ord t)e naios ser%er needs to use to remotely access t)eNS+lientBB aent

PSettinsQ

R9 O&CUS+A2ED #ASS*O!D

R 2)is is t)e same as t)e .ass$ord o.tion ,ut )ere you can store t)e.ass$ord in an o,fuscated manner

R NO2I+E o,fuscation is NO2 t)e same as encry.tion someone$it) access to t)is file can still fiure out t)e

R .ass$ord Its ust a ,it )arder to do it at first lance

Ro,fuscated.ass$ord?T$AUUd4lAAU$ASDAA&

R

R9 #ASS*O!D



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R 2)is is t)e .ass$ord 3-s5 t)at is re"uired to access NS+lient remotelyIf you lea%e t)is ,lan( e%eryone $ill ,e a,le to access t)e daemonremotly

pass&ord(#;.ecure-ass&ord

> Start t)e NS+lientBB Ser%ice

Start t)e NS+lientBB ser%ice

eit)er from t)e +ontrol #anel -K Administrati%e tools -K Ser%ices -KSelect VNS+lient.. 3Naios5 711> ;W-7-1; $7;X and clic( onstart 3or5 +lic( on VStart -K All #rorams -K NS+lientBB -K Start

NS+lientBB 3*in7;5 -lease note that this &ill start the N.Client??as a &indo&s serice

Later if you modify anyt)in in t)e NS+ini file you s)ould restart t)eVNS+lient.. 3Naios5 711> ;W-7-1; $7;X from t)e $indo$sser%ice

M i i *i d M )i


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@erify t)at t)e $indo$s-ser%er tem.late is ena,led under/usr/local/nagios/etc/ob5ects/templatescg

9 *indo$s )ost definition tem.late - 2)is is NO2 a real )ost ust a tem.late

define )ostY

name $indo$s-ser%erR 2)e name of t)is )ost tem.late

use eneric-)ost R In)erit default %alues from t)e eneric- )ost tem.late

c)ec(.eriod ;>xZ R &y default *indo$s ser%ers are monitored round t)e cloc(

c)ec(inter%al R Acti%ely c)ec( t)e ser%er e%ery minutes



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retry$interval % & #chedule host chec retries at %!inute intervals

!a'$chec$atte!pts %( & Chec each server %( ti!es)!a'*

chec$co!!and chec+host+alive & efault co!!and to chec ifservers are -alive-

notification$period /'0 & #end notification out at any ti!e+ day or night

notification$interval 1( & 2esend notifications every 1(!inutes

notification$options d,r & 3nly send notifications forspecific host statescontact$groups ad!ins & Notifications get sent to the

ad!ins by default

i i i d )i


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)ostrou.s $indo$s-ser%ers R Host rou.s t)at *indo$sser%ers s)ould ,e a mem,er of

reister R DON2 !EGIS2E! 2HIS : I2STUS2 A 2EM#LA2E

[

; Uncomment &indo&scg in /usr/local/nagios/etc/nagioscg

9 Definitions for monitorin a *indo$s mac)ine

cffile?0usr0local0naios0etc0o,ects0$indo$scf

M i i *i d M )i


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address 1\;16W1> R I# address of t)e remote $indo$s)ost

[

> 6eine &indo&s serices that should be monitored

Collo$in are t)e default $indo$s ser%ices t)at are already ena,led int)e sam.le $indo$scf Ma(e sure to u.date t)e )ostname on t)eseser%ices to reflect t)e )ostname defined in t)e a,o%e ste.

define ser%iceY

use eneric-ser%ice

)ostname remote-$indo$s-)ost

ser%icedescri.tion NS+lientBB @ersion

c)ec(command c)ec(nt+LIEN2@E!SION

[



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define ser%iceYuse eneric-ser%ice


ser%icedescri.tion U.time

c)ec(command c)ec(ntU#2IME

[

define ser%iceY

use eneric-ser%ice)ostname remote-$indo$s-)ost

ser%icedescri.tion +#U Load

c)ec(command c)ec(nt+#ULOAD-l W\

[



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define ser%iceYuse eneric-ser%ice



c)ec(command c)ec(ntU#2IME

[

define ser%iceY

use eneric-ser%ice)ostname remote-$indo$s-)ost

ser%icedescri.tion +#U Load

c)ec(command c)ec(nt+#ULOAD-l W\

[



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Enable -ass&ord -rotection

If you s.ecified a .ass$ord in t)e NS+ini file of t)e NS+lientBBconfiuration file on t)e *indo$s mac)ine

you]ll need to modi# the chec$:nt commanddefinition to include t)e.ass$ord

Modify t)e /usr/local/nagios/etc/commandscg file and addpass&ordas s)o$n ,elo$

define commandY

commandname c)ec(nt

commandline ÛSE!1^0c)ec(nt -H ^HOS2ADD!ESS^ -. 1;>W\-s My;Secure^#ass$ord -% Â!G1^ Â!G;^

[



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H 0eri# Coniguration and Restart Nagios@erify t)e naios confiuration files as s)o$n ,elo$

Pnaios-ser%erQ90usr/local/nagios/bin/nagios '

/usr/local/nagios/etc/nagioscg

2otal *arnins/

2otal Errors/

2)ins loo( o(ay - No serious .ro,lems $ere detected durin t)e .re-fli)t c)ec(



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I 4erie&%

Collo$in t)ree ste.s $ill )a..en on a %ery )i) le%el $)en Naios 3installed on t)enaios-ser%ers5 monitors a ser%ice 3for e dis( s.ace usae5 on t)e remote Linux )ost

Nagios &ill execute chec$:nrpe command on naios-ser%er and re"uest it to monitordis( usae on remote )ost usin c)ec(dis( command

2)e chec$:nrpe on the nagios'serer &ill contact the NR-E daemon on remote

)ost and re"uest it to execute t)e c)ec(dis( on remote )ost

2)e results of t)e chec$:dis$ command $ill ,e returned ,ac( ,y NR-E daemon tot)e chec$:nrpeon naios-ser%er



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II steps to install Nagios -lugins and NR-E on the remote host8 6o&nload Nagios -lugins and NR-E *dd'on

Do$nload follo$in files from Naiosor and mo%e to0)ome0do$nloads/

nagios'plugins'8>88targA nrpe';8;targA


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Premote)ostQ9 /conigure ''&ith'nagios'user(nagios ''&ith'nagios'group(nagios ''enable'redhat'pthread'&or$around

Premote)ostQ9 ma(e

Premote)ostQ9 ma(e install

Premote)ostQ9 c)o$n naiosnaios 0usr0local0naios Premote)ostQ9 c)o$n -! naiosnaios 0usr0local0naios0li,exec0

Note/ 4n Red Jat" For me the /conigure command &as hanging

&ith the the message% Kchec$ing or redhat spopen problemM*dd ''enable'redhat'pthread'&or$around to the /conigurecommand as a &or$'around or the aboe problem



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.etup NR-E to run as daemon 7ie as part o xinetd9% Modify t)e 0etc0xinetdd0nr.e to add t)e i.-address of t)e Naios

monitorin ser%er to t)e onlyfrom directi%e

Note t)at t)ere is a s.ace after t)e 1;Z1 and t)e naiosmonitorin ser%er i.-address 3in t)is exam.le naios monitorin ser%eri.-address is/ 1\;16W1;5

onlyfrom ? 1;Z18;8HD8;

Modify t)e /etc/sericesand add t)e follo$in at t)e end of t)e file

nrpe HHH/tcp ) NR-E

Start t)e ser%ice

Premote)ostQ9serice xinetd restart



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Monitor !emote Linux Host 0eri# &hether NR-E is listening

Premote)ostQ9 netstat -at _ re. nr.e

tc. /nr.e / LIS2EN

0eri# to ma$e sure the NR-E is unctioning properl#

Premote)ostQ9 0usr0local0naios0li,exec0c)ec(nr.e -H local)ost

N!#E %;1;

H odi# the /usr/local/nagios/etc/nrpecg

2)e nr.ecf file located on t)e remote )ost contains t)e commandst)at are needed to c)ec( t)e ser%ices on t)e remote )ost

&y default t)e nr.ecf comes $it) fe$ standard c)ec( commands assam.les

c)ec(users and c)ec(load are s)o$n ,elo$ as an exam.le



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commandPc)ec(usersQ?0usr0local0naios0li,exec0c)ec(users -$ -c 1commandPc)ec(loadQ?0usr0local0naios0li,exec0c)ec(load -$ 11 -c7;;

In all t)e c)ec( commands t)e V'&M stands or K3arningM and V'cMstands or KCriticalM

for e in t)e c)ec(dis( command ,elo$ if t)e a%aila,le dis( s.ace etsto ;` of less naios $ill send $arnin messae

If it ets to 1` or less naios $ill send critical messae +)ane t)e%alue of V-c and V-$ .arameter ,elo$ de.endin on your en%ironment

commandchec$:dis$O(/usr/local/nagios/libexec/chec$:dis$ '& ;BP 'c8BP 'p /de/hda8



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III >Coniguration steps on the Nagios monitoring serer to monitor remote host%

8 6o&nload NR-E *dd'on

Do$nload nr.e-;1;tar= from Naiosor and mo%e to 0)ome0do$nloads/te/

; Install chec$:nrpe on the nagios monitoring serer

Pnaios-ser%erQ9 tar x%f= nr.e-;1;tar=

Pnaios-ser%erQ9 cd nr.e-;1;

Pnaios-ser%erQ9 0confiure

Pnaios-ser%erQ9 ma(e all



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Pnaios-ser%erQ9 ma(e install-.luin 0confiure $ill i%e a confiuration summary as s)o$n ,elo$/

+onfiuration summary for nr.e ;1; -71-;W /

General O.tions/

JJJJJJJJ-

N!#E .ort/ 666

N!#E user/ naios

N!#E rou./ naios

Naios user/ naios

Naios rou./ naios



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Note/ I got the Kchec$ing or ..L headers conigure% error%Cannot ind ssl headersMerror messae $)ile .erformin 0confiure Install o.enssl-de%el as s)o$n ,elo$ and runt)e 0confiure aain to fix t)e .ro,lem

Pnaios-ser%erQ9 r.m -i%) o.enssl-de%el-\Za->716i7W6r.m (r,-de%el-17>->Zi7W6r.m=li,-de%el-1;1;-1;i7W6r.m e;fs.ros-de%el-17-1;

el>i7W6r.m

$arnin/ o.enssl-de%el-\Za->716i7W6r.m/ @7 DSA sinature/ NOE8 (ey ID d,>;a6e

#re.arin 9999999999999999999999999999999999999999999 P1`Q

1/e;fs.ros-de%el 9999999999999999999999999999999999999999999 P ;`Q

;/(r,-de%el 9999999999999999999999999999999999999999999 P `Q



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host deinition sample% define )ostY

use linux-ser%er

)ostname remote)ost

alias !emote Host

address 1\;16W17

contactrou.s admins

[



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Ser%ice definition sam.le/

define ser%iceY

use eneric-ser%ice

ser%icedescri.tion !oot #artition

contactrou.s admins

c)ec(command c)ec(nr.ec)ec(dis(

[

Note/ In all t)e a,o%e exam.les re.lace remote)ost $it) t)e corres.ondin)ostname of your remote)ost



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> Restart the nagios serice!estart t)e naios as s)o$n ,elo$ and loin to t)e naios $e,3)tt./00naios-ser%er0naios05 to %erify t)e status of t)e remote)ost linuxse%er t)at $as added to naios for monitorin

Pnaios-ser%erQ9 serice nagios reload

Monitor Net$or( S$itc) and #orts


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= *dd a ne& host or the s&itch to be moniteredIn t)is exam.le I]%e defined a )ost to monitor t)e core s&itch in t)e/usr/local/nagios/etc/ob5ects/s&itchcgfile

+)ane t)e address directi%e to your s$itc) i.-address accordinly

define )ostY use eneric-s$itc)

)ostname core's&itch

alias +isco +ore S$itc)

address 8;8HD8B

)ostrou.s s$itc)es

[



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> *dd common serices or all s&itches

Dis.layin t)e uptime o the s&itchand

%erifyin $)et)er s&itch is alieare common ser%ices for all s$itc)es

So define t)ese ser%ices under t)e s$itc)es )ostrou.name as s)o$n ,elo$

9 Ser%ice deinition to ping the s&itch using chec$:ping

define ser%iceY

use eneric-ser%ice

)ostrou.name s$itc)es

ser%icedescri.tion #ING

c)ec(command c)ec(.in;;`66`

normalc)ec(inter%al

retryc)ec(inter%al 1

[



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9 Ser%ice definition to monitor s$itc) u.time usin c)ec(snm.

define ser%iceY

use eneric-ser%ice

)ostrou.name s$itc)es


c)ec(command c)ec(snm.-+ .u,lic -o sysU.2ime

[



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H *dd serice to monitor an actie s&itch portUse chec$:snmp to monitor the speciic portas s)o$n ,elo$

2)e follo$in t$o ser%ices monitors .ort91 and .ort9 2o add additional.orts c)ane t)e %alue ifO.erStatusn accordinly ie n defines t)e .ort9

9 Monitor status of .ort num,er 1 on t)e +isco core s$itc) define ser%iceY

use eneric-ser%ice

)ostname core-s$itc)

ser%icedescri.tion #ort 1 Lin( Status

c)ec(command c)ec(snm.-+ .u,lic -o ifO.erStatus1 -r 1 -m!C+1;17-MI&

[



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9 Monitor status of .ort num,er on t)e +isco core s$itc) define ser%iceY

use eneric-ser%ice


ser%icedescri.tion #ort Lin( Status c)ec(command c)ec(snm.-+ .u,lic -o ifO.erStatus -r 1 -m !C+1;17-MI&

[



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*dd serices to monitor multiple s&itch ports togetherSometimes you may need to monitor the status o multiple portscom,ined toet)er

ie Naios s)ould send an alert" een i one o the port is do&n

In t)is case define t)e follo$in ser%ice to monitor multi.le .orts

9 Monitor .orts 1 - 6 on t)e +isco core s$itc) define ser%iceY

use eneric-ser%ice


ser%icedescri.tion #orts 1-6 Lin( Status

c)ec(command c)ec(snm.-+ .u,lic -o ifO.erStatus1 -r 1 -m !C+1;17-MI& -oifO.erStatus; -r 1 -m !C+1;17-MI& -o ifO.erStatus7 -r 1 -m !C+1;17-MI& -oifO.erStatus> -r 1 -m !C+1;17-MI& -o ifO.erStatus -r 1 -m !C+1;17-MI& -oifO.erStatus6 -r 1 -m !C+1;17-MI&



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9 0etc0rcd0initd0naios sto. Sto..in naios/ done

9 0etc0rcd0initd0naios start

Startin naios/ done

@erify t)e status of t)e s$itc) from t)e Naios $e, UI/ )tt./00Ynaios-ser%er[0naios as s)o$n ,elo$/



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Resource File7s9

!esource files can ,e used to store user'deined macros

2)e main .oint of )a%in resource files is to use them to store sensitieconiguration inormation 7li$e pass&ords9"$it)out ma(in t)em a%aila,le tot)e +GIs

Cormat/ resource:ile(Qile:name

Example%

resource:ile(/usr/local/nagios/etc/resourcecg



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&ain Configuration 'ile

2)e main confiuration file contains a num,er of directi%es t)at affect )o$t)e Naios daemon o.erates

2)is conig ile is read b# both the Nagios daemonand t)e +GIs

2his is &here #ouSre going to &ant to get started in #our conigurationadentures

Conig File Location

2)e main confiuration file is usually named nagioscg and located int)e /usr/local/nagios/etc/ director#



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CGI Coniguration File

2)e +GI confiuration file contains a number o directies that aect theoperation o the CGIs

It also contains a reference t)e main confiuration file

so t)e +GIs (no$ )o$ you]%e confiured Naios and

$)ere your o,ect defintions are stored

* sample CGI coniguration ile 7/usr/local/nagios/etc/cgicg9 is installed or

#ou &hen #ou follo$ t)e "uic(start installation uide


Main confiuration file o.tions


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Lo Cile

Cormat/ log:ile(Qile:name

Exam.le/

log:ile(/usr/local/nagios/ar/nagioslog

2)is %aria,le s.ecifies $)ere Naios s)ould create its main lo file

2)is s)ould ,e t)e first %aria,le t)at you define in your confiuration file as Naios$ill try to $rite errors t)at it finds in t)e rest of your confiuration data to t)is file

If you )a%e lo rotation ena,led t)is file $ill automatically ,e rotated e%ery )ourday $ee( or mont)




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2emp File

Cormat/ tem.file?filenameK

Exam.le/

temp:ile(/usr/local/nagios/ar/nagiostmp

2)is is a tem.orary file t)at Naios .eriodically creates to use $)en u.datin commentdata status data etc

+onfiuration o%er%ie$Main confiuration file o.tions


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.tatus File

Cormat/ status:ile(Qile:name

Exam.le/

status:ile(/usr/local/nagios/ar/statusdat

2)is is t)e file t)at Naios uses to store t)e current status comment and do$ntime information

2)is file is used ,y t)e +GIs so t)at current monitorin status can ,e re.orted %ia a $e, interface

2)e +GIs must )a%e read access to t)is file in order to function .ro.erly

Note/ 2)is file is deleted e%ery time Naios sto.s and recreated $)en it starts

O,ect confiuration o%er%ie$


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3hat *re 4b5ects1

O,ects are all t)e elements t)at are in%ol%ed in t)e monitorin and notificationloic 2y.es of o,ects include/

.erices .erice Groups Josts Jost Groups Contacts Contact Groups Commands 2ime -eriods Notiication Escalations Notiication and Execution 6ependencies



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3here *re 4b5ects 6eined1

O,ects can ,e defined in one or more confiuration files and0or directories t)at yous.ecify usin t)ecg:ileand0orcg:dirdirecti%es in t)e main confiuration file

Ho$ Are O,ects Definedb

O,ects are defined in a flexi,le tem.late format $)ic) can ma(e it muc) easier tomanae your Naios confiuration in t)e lon term



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Host Grou.s are rou.s of one or more )osts

Host rou.s can ma(e it easier to

315 %ie$ t)e status of related )osts in t)e Naios $e, interface and

3;5 sim.lify your confiuration t)rou) t)e use of o,ect tric(s



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.ericesare one of t)e central o,ects in t)e monitorin loic

Ser%ices are associated $it) )osts and can ,e/

*ttributes o a host 7C-U load" dis$ usage" uptime" etc9

.erices proided b# the host 7J22-" -4-=" F2-" ..J" etc9

4ther things associated &ith the host 76N. records" etc9



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Ser%ice Grou.s are rou.s of one or more ser%ices

Ser%ice rou.s can ma(e it easier to

315 %ie$ t)e status of related ser%ices in t)e Naios $e, interface and

3;5 sim.lify your confiuration t)rou) t)e use of o,ect tric(s



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www.gnugroup.org 83

2imeperiodsare are used to control/

*)en )osts and ser%ices can ,e monitored

*)en contacts can recei%e notifications



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www.gnugroup.org 84

Commandsare used to tell Naios $)at .rorams scri.ts etc it s)ould

execute to .erform/

Host and ser%ice c)ec(s

Notifications

E%ent )andlers

and more

O,ect Definitions

Introduction


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*it) Naios youFre oin to monitor )osts and ser%ices

&ein a flexi,le frame$or( Naios lets you define t)ose yourself as o,ectdefinitions in confiuration files

*)en creatin and0or editin confiuration files (ee. t)e follo$in in mind/

Lines t)at start $it) a F9F c)aracter are ta(en to ,e comments and are not.rocessed

Directi%e names are case-sensiti%e

+)aracters t)at a..ear after a semicolon 3R5 in confiuration lines are treatedas comments and are not .rocessed

#at) 0usr0local0naios0etc0o,ect0

O,ect Definitions


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Jost 6einition

Host monitorin only tells you if a )ost is u. ieres.ondin to a .in from t)e Naios ser%er

A sam.le definition of a )ost is as follo$s/

define )ost Y )ostname

linux,ox1 )ostrou.s

linuxser%ers alias Linux

Ser%er 1 address 1;1 c)ec(command c)ec(-)ost-ali%e c)ec(inter%al retryinter%al 1 maxc)ec(attem.ts c)ec(.eriod ;>xZ contactrou.s l inux-admins notificationinter%al 7 notification.eriod ;>xZ notificationo.tions dur

[

2)e slide defines a Linux ,ox t)at $ill uset)e chec$'host'alie command to ma(esure t)e ,ox is u. and runnin

2)e test $ill ,e .erformed e%ery fi%eminutes

and after fi%e failed tests

it $ill assume t)e )ost is do$n

If it is do$n a notification $ill ,e sent oute%ery 7 minutes

O,ect Definitions


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6etermining .tatus and Reachabilit# o Net&or$ Josts

Naios is a,le to determine $)et)er t)e )osts youFre monitorin are in a 643N orUNRE*CJ*TLE state

2)ese are %ery different 3alt)ou) related5 states and can )el. you "uic(ly

determine t)e root cause of net$or( .ro,lems

HereFs )o$ t)e reac)a,ility loic $or(s to distinuis) ,et$een t)ese t$o states

O,ect Definitions

i i d


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6etermining .tatus andReachabilit# o Net&or$ Josts

2a(e a loo( at t)e sim.le net$or(diaram Cor t)is exam.le letsassume youFre monitorin all t)e )osts3ser%er routers s$itc)es etc5 t)at are.ictured Naios is installed andrunnin on t)e Naios )ost

O,ect Definitions


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6eining -arent/Child Relationships

No$ t)at you (no$ $)at t)e .arent0c)ild

relations)i.s loo( li(e for )osts t)at are

,ein monitored )o$ do you confiure Naios to reflect

t)emb

2he parents directie in #our hostdeinitions

allo&s #ou to do this

O,ect Definitions


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6eining -arent/Child Relationships

define )ostY

)ostname Nagios R -- 2)e local )ost )as no .arent - it is t)eto.most )ost

[

O,ect Definitions


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define )ost

Y

)ostname 3eb

.arents .&itch8

[

define )ost

Y

)ostname tp

.arents .&itch8

[

define )ost

Y

)ostname tp

.arents .&itch8

[

define )ost

Y

)ostname .&itch;

.arents Router8

[

define )ost

Y

)ostname Router8

.arents .&itch8

[

O,ect Definitions


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Reachabilit# Logic in *ction

No$ t)at youFre confiured Naios$it) t)e .ro.er .arent0c)ildrelations)i.s for your )osts

letFs see $)at )a..en $)en .ro,lems

arise

Assume t)at t$o )osts - 3eb andRouter8 ' go oline

O,ect Definitions


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*)en )osts c)ane state 3ie fromU# to DO*N5

t)e )ost reac)a,ility loic in Naios(ic(s in

2)e reac)a,ility loic $ill initiate.arallel c)ec(s of t)e .arents andc)ildren of $)ate%er )osts c)anestate

2)is allo$s Naios to "uic(lydetermine t)e current status of yournet$or( infrastructure $)en c)anesoccur

O,ect Definitions



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Final conclusion Naios $ill determine t)at *e, and !outer1

are ,ot) in DO*N states ,ecause t)e .at)to t)ose )osts is not ,ein ,loc(ed

Naios $ill determine t)at all t)e )osts,eneat) !outer1 are all in anUN!EA+HA&LE state ,ecause Naios canFtreac) t)em

!outer1 is DO*N and is ,loc(in t)e .at) tot)ose ot)er )osts

2)ose )osts mi)t ,e runnin fine or t)eymi)t ,e offline -

Naios doesnFt (no$ ,ecause it canFt reac)t)emJence Nagios considers them to beUNRE*CJ*TLE instead o 643N

O,ect Definitions

define )ostrou. define )ostrou.


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Y

)ostrou.name linux-ser%ers

Alias Linux ser%ers

Mem,ers linux,ox1linux,ox;

[

Y

)ostrou.name aix-ser%ers

Alias AI4 ser%ers

Mem,ers aix,ox1aix,ox;

[

define )ostrou.

Y

)ostrou.name unix-ser%ers

Alias UNI4 ser%ers

Mem,ers llinux-ser%ersaix-ser%ers

[

hostgroup:nameS)ort uni"ue name of t)e)ost rou.

alias Descri.ti%e name of t)e )ost rou.

members List of all )osts t)at s)ould ,e amem,er of t)is rou. se.arated ,y commas

hostgroup:members List of all ot)er )ostrou.s $)ose mem,ers s)ould also ,emem,ers of t)is rou. se.arated ,y commas

O,ect Definitions

Host Group Definition


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4ost groups can also be used when defining services or dependencies."or e'a!ple,

it is possible to tell Nagios that all 5inu' servers should have their ##4service !onitored and

all 6I7 servers should have a telnet accepting connections.

It is also possible to define dependencies between hosts They are, in a way, si!ilar to a parent+host relationship, butdependencies offer !ore co!ple' configuration options.

Nagios will only issue host and service checs if all dependant hosts are

currently up

O,ect Definitions


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Service Group Definition#ervices can be grouped in a si!ilar way to host ob8ects

This can be done to !anage services !ore conveniently.

It also aids in viewing service reports on the Nagios web interface.

#ervice groups are also used to configure dependencies in a !oreconvenient way.

O,ect Definitions

Contact Definition


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Contact Definition

Contacts define people who can either be owners of specific !achines,or people who should be contacted in case of proble!s.

epending on how your organi9ation chooses to contact people in caseof proble!s, the definition of a contact !ay vary a lot.

6 contact consists of a uni:ue na!e, a descriptive na!e, and one or!ore e!ail addresses and;or pager nu!bers.

Contact definitions can also contain additional data specific to how aperson can be contacted.

O,ect Definitions

Contact Definition


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Contacts can be grouped. Asually, grouping is used to eep a list ofwhich users are responsible for which tass,

and the group !aps to 8ob responsibilities for particular people.

It also !aes it possible to define people who should be responsible for handling proble!s at specific ti!e periods,

and Nagios will auto!atically contact the right people depending on theti!e at which a proble! has occurred.

It is also possible to specify different people or groups for handling host+related and service+related proble!sB

for example, hardware ad!inistrators for handling host proble!s andsyste! ad!inistrators for handling service issues.

O,ect Definitions

Ti i d D fi iti


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Time eriod Definition

Ti!eperiod definitions allow you to control when variousaspects of the !onitoring and alerting logic can operate.

"or instance, you can restrict

When regularly scheduled host and service checs can beperfor!ed When notifications can be sent out When notification escalations can be used When dependencies are valid

O,ect DefinitionsHow Time eriods !ork !ith Service Checks

Without the i!ple!entation of ti!e periods, Nagios would !onitor all


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services that you had defined / hours a day, 0 days a wee.

While this is fine for !ost services that need !onitoring, it doesnDt worout so well for others.

"or instance, do you really need to !onitor printers all the ti!e whentheyDre really only used during nor!al business hours?

Eerhaps you have develop!ent servers which you would prefer to haveup, but arenDt -!ission critical- and therefore donDt have to be !onitoredfor proble!s over the weeend.

Ti!e period definitions now allow you to have !ore control over whensuch services !ay be checed...

O,ect Definitions


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define time.eriodY time.eriodname admin1-oncall

alias Admin1 On +all

;\->-1Z 0 1> 1/-;>/

;\->-1W 0 1> /-;>/

;\->-1\ 0 1> /-;>/

;\->-; 0 1> /-;>/

;\->-;1 0 1> /-;>/

;\->-;; 0 1> /-;>/

;\->-;7 0 1> /-;>/

;\->-;> 0 1> /-1/

[

define time.eriodY time.eriodname admin;-oncall

alias Admin; On +all

;\->-;> 0 1> 1/-;>/

;\->-; 0 1> /-;>/

;\->-;6 0 1> /-;>/

;\->-;Z 0 1> /-;>/

;\->-;W 0 1> /-;>/

;\->-;\ 0 1> /-;>/

;\->-7 0 1> /-;>/

;\--1 0 1> /-1/

[

O,ect Definitions


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Command Definition


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#ervice dependencies wor in a si!ilar way as hostdependencies.

"or services dependencies, you need to define a !asterservice and a dependent service

"or e'a!ple,you can tell Nagios that E3E1 services on the e!ailservershost group depend on the 56E service on the ldapserverhost.

O,ect Definitions

Service Dependency Definition


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Host Dependency Definition


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.erice Escalation 6einition

Ser%ice escalations are com.letelyo.tional and are used to escalate

notifications for a .articular ser%ice

define ser%iceescalationY)ostname $e,ser%er

ser%icedescri.tion H22#

firstnotification 7

lastnotification

notificationinter%al \

contactrou.s nt-adminsmanaers

[

define ser%iceescalationY

)ostname

$e,ser%er

;7>

ser%icedescri.tion H22#

firstnotification 6

lastnotification 1

notificationinter%al 6

contactrou.s nt-adminsmanaerse%eryone

[

O,ect Definitions


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Jost escalations 6einitionHost escalations are com.letelyo.tional and are used to escalatenotifications for a .articular )ost

define )ostescalationY)ostname router-7>

firstnotification

lastnotification W

notificationinter%al 6

contactrou.s all-router-admins

[

define )ostescalationY

)ostname router-7>

firstnotification \

lastnotification ;

notificationinter%al 6contactrou.s all-net$or(-manaer

[

!unnin Naios


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Starting and Stopping "agios

Start "agios#$ %nit Script&

The easiest way to start the Nagios dae!on is by using the init script lie

so'etc'rc(d'init(d'nagios start

)$ *anually& Hou can start the Nagios dae!on !anually with the +dco!!and line option lie so'usr'local'nagios'+in'nagios ,d 'usr'local'nagios'etc'nagios(cfg

!unnin Naios

Starting and Stopping "agios

-estarting "agios


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-estarting "agios2estarting;reloading is nececessary when you !odify your configuration

files and want those changes to tae effect.

#$ %nit Script&The easiest way to restart the Nagios dae!on is by usingthe init script lie so ;etc;rc.d;init.d;nagios reload

)$ !e+ %nterface&Hou can restart the Nagios through the webinterface by clicing the -Erocess Info-navigation lin andselecting -2estart the Nagios process-

!unnin NaiosStarting and Stopping "agios

Stopping "agios

#$ %nit Script&he easiest way to stop the Nagios dae!on is by using the


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init script lie so ;etc;rc.d;init.d;nagios stop

)$ !e+ %nterface& Hou can stop the Nagios through the web interfaceby clicing the -Erocess Info- navigation lin and selecting -#hutdownthe Nagios process-

.$ *anually&Hou can stop the Nagios process by sending it a #IT


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1 2)e )ost )as c)aned its state to DO*N or UN!EA+HA&LE stateR notificationis sent out after firstnotificationdelay num,er of minutes s.ecified int)e corres.ondin )ost o,ect

;2)e )ost remains in DO*N or UN!EA+HA&LE stateR notification is sent oute%ery notificationinter%al num,er of minutes s.ecified in t)e corres.ondin

)ost o,ect 7 Host reco%ers to an U# stateR notification is sent out immediately and only once

>Host starts or sto.s fla..inR notification is sent out immediately

Host remains fla..inR notification is sent out e%ery notificationinter%al num,er

of minutes s.ecified in t)e corres.ondin )ost o,ect

Notifications

Notiications ma# be sent out in one o the ollo&ing situations%

6 Ser%ice )as c)aned its state to *A!NING +!I2I+AL or UNNO*N stateR notification is sent out after first notification delay num,er of minutes s.ecified in


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notification is sent out after firstnotificationdelay num,er of minutes s.ecified int)e corres.ondin ser%ice o,ect

Z Ser%ice remains in *A!NING +!I2I+AL or UNNO*N stateR notification issent out e%ery notificationinter%al num,er of minutes s.ecified in t)ecorres.ondin ser%ice o,ect

W Ser%ice reco%ers to an O stateR notification is sent out immediatelyand only once

\ Ser%ice starts or sto.s fla..inR notification is sent out immediately

1 Ser%ice remains fla..inR notification is sent out e%ery notificationinter%al num,er of minutes s.ecified in t)e corres.ondin ser%ice o,ect

If one of t)ese conditions occurs Naios starts e%aluatin $)et)er informationa,out it s)ould ,e sent out and to $)om

Notifications

*)o Gets Notifiedb


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Eac) )ost and ser%ice definition )as a contactrou.sK o.tion t)at s.ecifies $)atcontact rou.s recei%e notifications for t)at .articular )ost or ser%ice

+ontact rou.s can contain one or more indi%idual contacts

Notiication ethods

.aer+ell.)oneemailinstant messaeaudio alertetc

Host +)ec(s

*)en Are Host +)ec(s #erformedb


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Hosts are c)ec(ed ,y t)e Naios daemon/At reular inter%als as defined ,y t)e c)ec(inter%al and retryinter%al o.tions inyour )ost definitions

On-demand $)en a ser%ice associated $it) t)e )ost c)anes state

On-demand as needed as .art of t)e )ost reac)a,ility loic

On-demand as needed for .redicti%e )ost de.endency c)ec(s

Ser%ice +)ec(s

*)en Are Ser%ice +)ec(s #erformedb


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Ser%ices are c)ec(ed ,y t)e Naios daemon/At reular inter%als as defined ,y t)e c)ec(inter%al and retryinter%al o.tions inyour ser%ice definitions

On-demand as needed for .redicti%e ser%ice de.endency c)ec(s

Acti%e +)ec(s


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Naios is ca.a,le of monitorin )osts and ser%ices in t&o &a#s%actiel# and passiel#

Acti%e c)ec(s are t)e most common met)od for monitorin )ostsand ser%ices 2)e main features of acti%es c)ec(s as as follo$s/

Acti%e c)ec(s are initiated ,y t)e Naios .rocess

Acti%e c)ec(s are run on a reularly sc)eduled ,asis

Jo& *re *ctie Chec$s -erormed1

Acti%e c)ec(s are initiated ,y t)e c)ec( loic in t)e Naios daemon

*)en Naios needs to c)ec( t)e status of a )ost or ser%ice it $illexecute a .luin and .ass it information a,out $)at needs to ,ec)ec(ed

2)e .luin $ill t)en c)ec( t)e o.erational state of t)e )ost or ser%iceand re.ort t)e results ,ac( to t)e Naios daemon

Naios $ill .rocess t)e results of t)e )ost or ser%ice c)ec( and ta(ea..ro.riate action as necessary 3e send notifications run e%ent

)andlers etc5

#assi%e +)ec(s


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State 2y.esJost .tates Hosts t)at are c)ec(ed can ,e in one of t)ree different states/

U#


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DO*N

UN!EA+HA&LE

Jost .tate 6eterminationHost c)ec(s are .erformed ,y .luins $)ic) can return a state of

O

*A!NING

UNNO*N or

+!I2I+AL

State 2y.esJost .tates#luin !esult #reliminary Host State

O U#


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*A!NING U# or DO*N

UNNO*N DO*N

+!I2I+AL DO*N

#reliminary Host State #arent Host State Cinal Host State

DO*N At least one .arent is U# DO*N

DO*N All .arents are eit)er UN!EA+HA&LE

DO*N or UN!EA+HA&LE

State 2y.esJost .tate Changes.ot .tates

.ot states occur in the ollo&ing situations


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15 *)en a ser%ice or )ost c)ec( results in a non-O or non-U# state and t)eser%ice c)ec( )as not yet ,een 3re5c)ec(ed t)e num,er of times s.ecified ,y t)emaxc)ec(attem.ts directi%e in t)e ser%ice or )ost definition 2)is is called asoft error

;5 *)en a ser%ice or )ost reco%ers from a soft error 2)is is considered a soft reco%ery

2he ollo&ing things occur &hen hosts or serices experience .4F2 statechanges%

2)e SOC2 state is loed

E%ent )andlers are executed to )andle t)e SOC2 state

2)e only im.ortant t)in t)at really )a..ens durin a soft state is t)e execution ofe%ent )andlers

Usin e%ent )andlers can ,e .articularly useful if you $ant to try and .roacti%ely fix a.ro,lem ,efore it turns into a HA!D state

State 2y.esJost .tate ChangesJard .tates

Jard states occur or serices in the ollo&ing situations


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15 *)en a ser%ice c)ec( results in a non-O state and it )as ,een 3re5c)ec(ed t)enum,er of times s.ecified ,y t)e maxc)ec(attem.tsK o.tion in t)e ser%icedefinition 2)is is a )ard error state

;5 *)en a ser%ice reco%ers from a )ard error state 2)is is considered to ,e a )ard

!eco%ery75 *)en a ser%ice c)ec( results in a non-O state and its corres.ondin )ost is eit)er

DO*N or UN!EA+HA&LE

&hat happens &hen a host or serice is in a hard state%

)anes from a )ard O state to a )ard non-O state

c)anes from a )ard non-O state to a )ard O-state

c)anes from a )ard non-O state of some (ind to a )ard non-O state ofanot)er (ind

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Nagios Module 1