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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">What is Nagios ?</span></h4>
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Nagios is an Open Source monitoring tool, its provides you monitoring environment to keep an eye on your different machines wheather its window machine or linux machine.<br />
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With Nagios, we can monitor remote hosts and their services on a single window. It will show you warnings and indicates if something goes wrong on your servers which eventually helps you to detect problems before they occur. It helps you to reduce downtime and business losses.</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">Configure RPMForge and EPEL repository:</span></h4>
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<strong>Download and install rpmforge repository 32 bit:</strong><br />
# wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.i686.rpm<br />
# rpm -Uvh rpmforge-release-0.5.2-2.el6.rf.i686.rpm<br />
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<strong>Download and install epel repository 32 bit:</strong><br />
# wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm<br />
# rpm -ivh epel-release-6-8.noarch.rpm</div>
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<strong>If you get below error for epel repository:</strong><br />
“Cannot retrieve metalink for repository: epel. Please verify its path and try again”<br />
<strong>then run this command:</strong><br />
# sudo yum upgrade ca-certificates –disablerepo=epel</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">Different Configuration files used in Nagios:</span></h4>
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<strong>nagios.cfg:</strong> The primary nagios configuration file where lots of global parameters are there. In this file we add path of the newly added linux, windows machine as well as switch or routers. Whatever we like to monitor on nagios we have to add that device file path here.<br />
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<strong>cgi.cfg:</strong> configuration information for nagios web interface.This include path of the primary configuration file called nagios.cfg.This file also contains user information who is authorized to nagios.</div>
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<strong>timeperiods.cfg:</strong> Define the timeperiods. for e.g. if you want a service to be monitored only during the business hours, define a time period called business hours and specify the hours that you would like to monitor. define the timeperiods with time templates. This config file provides you with some example time period definitions that you can reference in host, service, contact, and dependency definitions.</div>
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<strong>commands.cfg:</strong> All the commands to check services are defined here. You can use $HOSTNAME$ and $HOSTADDRESS$ macro on the command execution that will substitute the corresponding hostname or host ip-address automatically. This config file provides you with some example command definitions that you can reference in host, service, and contact definitions.</div>
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<strong>templates.cfg:</strong> Multiple host or service definition that has similar characteristics can use a template, where all the common characteristics can be defined. Use template is a time saver.</div>
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<strong>localhost.cfg:</strong> define the monitoring for local host as sample configuration file.</div>
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<strong>Printer.cfg:</strong> sample configuration file for printer.</div>
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<strong>Switch.cfg:</strong> sample configuration file for switch.</div>
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<strong>Windows.cfg:</strong> sample configuration file for windows machine.</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">what is NRPE and what nagios-plugins do?</span></h4>
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<strong>NRPE</strong> stands for Nagios Remote Plugin Executor. NRPE allows you to remotely execute Nagios plugins on other Linux/Unix & windows machines. This allows you to monitor remote machine metrics (disk usage, CPU load, webserver usage, database server usage, etc…,).<br />
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Nagios Plugins monitor hosts, devices, services, protocols, and applications with Nagios and give the report to NRPE. NRPE send those reports to Nagios server based on Nagios server request. So, Nagios & NRPE can perform all the process only with Nagios-plugins.</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">Installation on Nagios Server: (192.168.0.160)</span></h4>
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<strong>These are Required packages to install nagios:</strong><br />
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#yum install nagios<br />
#yum install nagios-plugins-all<br />
#yum install nagios–common<br />
#yum install nagios-nrpe<br />
#yum install nagios-plugins<br />
#yum install nagios-devel<br />
#yum install openssl-devel<br />
#yum install nagios-nsca<br />
#yum install nagios-plugins-nrpe<br />
#yum install nagios-nsca-client<br />
Check above packages that they are available on nagios server.</div>
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<strong>We need to add nrpe service under /etc/services with exact port number and protocol:</strong><br />
# vi /etc/services<br />
nrpe 5666/tcp #nrpe</div>
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<strong>Edit nrpe configuration file and add entry of nagios server ip:</strong><br />
# vim /etc/nagios/nrpe.cfg<br />
## the nagios monitoring server is permitted ##<br />
## NOTE: There is no space after the comma ##<br />
allowed_hosts=127.0.0.1,192.168.0.160<br />
#service nrpe restart</div>
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<strong>Check whether the service is listening or not.</strong><br />
# netstat –ntulp | grep nrpe</div>
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<strong>Now, add user “nagios” on server if not available.</strong><br />
# useradd nagios<br />
# passwd nagios</div>
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<strong>Nagios configuration: Open cgi.cfg file and replace default nagiosadmin user to nagios user.</strong><br />
# vi /etc/nagios/cgi.cfg<br />
use_authentication=1<br />
authorized_for_system_information=nagios<br />
authorized_for_configuration_information=nagios<br />
authorized_for_system_commands=nagios<br />
authorized_for_all_services=nagios<br />
authorized_for_all_hosts=nagios<br />
authorized_for_all_service_commands=nagios<br />
authorized_for_all_host_commands=nagios<br />
: wq!</div>
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<strong>Nagios password file: Add user nagios to the htpasswd.users file as follow:</strong><br />
# cd /etc/nagios<br />
# htpasswd –c htpasswd.users nagios<br />
# htpasswd htpasswd.users nagios</div>
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<strong>Now, copy “localhost.cfg” template as “server.cfg” for monitoring nagios server:</strong><br />
# cd /etc/nagios/objects/<br />
# cp localhost.cfg server.cfg</div>
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<strong>Open server.cfg file and make entry for hostname, alias and ip of linux pc.This to be done for host, hostgroup and services.</strong><br />
# vim server.cfg<br />
define host{<br />
use                       linux-server<br />
host_name        server<br />
alias                    server<br />
address              192.168.0.160<br />
}</div>
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define hostgroup{<br />
hostgroup_name            linux<br />
alias                                   Servers<br />
members                           server<br />
}</div>
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define service{<br />
use                                       local-service<br />
host_name                         server<br />
service_description           PING<br />
check_command       check_ping!100.0,20%!500.0,60%<br />
}</div>
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<strong>(NOTE:change hostname as “server” for rest of services as well)</strong></div>
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<strong>Verify configuration nagios configuration file for errors:</strong><br />
# nagios –v /etc/nagios/nagios.cfg</div>
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<strong>If there is no DNS configured then open httpd.conf file and make entry of server as:</strong><br />
# vim /etc/httpd/conf/httpd.conf<br />
ServerName 192.168.0.160:80<br />
: wq!</div>
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<strong>Open /etc/httpd/conf.d/nagios.conf file and check the “AuthUserFile” location for nagios access:</strong><br />
# vim /etc/httpd/conf.d/nagios.conf<br />
AuthUserFile /etc/nagios/htpasswd.users</div>
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<strong>Start the following services:</strong><br />
# service httpd start<br />
# chkconfig httpd on<br />
# service nagios start<br />
# chkconfig nagios on<br />
# service nrpe start<br />
# chkconfig nrpe on</div>
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<strong>Run below command to check whether the nrpe service is working and its listening or not:</strong><br />
#/usr/lib/nagios/pulgins/check_nrpe –H 192.168.0.160</div>
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<strong>Check the nagios console from web as with user nagios:</strong><br />
http://192.168.0.160/nagios</div>
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<strong>Check nagios log under:</strong><br />
# tail –f /var/log/nagios/nagios.log</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">Add Linux machine to nagios server for monitoring:(192.168.0.163)</span></h4>
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<strong>Install the following packages on client machine:</strong><br />
#yum install nagios-plugins-nrpe<br />
#yum install nagios-nrpe<br />
#yum install openssl-devel<br />
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<strong>Edit nrpe configuration file and add entry of nagios server ip:</strong><br />
# vim /etc/nagios/nrpe.cfg<br />
## the nagios monitoring server is permitted ##<br />
## NOTE: There is no space after the comma ##<br />
allowed_hosts=127.0.0.1,192.168.0.160</div>
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<strong>We need t0 add nrpe service under /etc/services with exact port number and protocol:</strong><br />
# vi /etc/services<br />
nrpe 5666/tcp #nrpe<br />
#service nrpe restart</div>
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<strong>Check whether the service is listening or not.</strong><br />
# netstat –ntulp | grep nrpe</div>
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<strong>Now, come to nagios server (192.168.0.160) machine:</strong><br />
# cd /etc/nagios/objects/<br />
# cp localhost.cfg linux.cfg<br />
<strong>Open linux.cfg file and make entry for hostname, alias and ip of linux pc.This to be done for host, hostgroup and services.</strong><br />
# vim linux.cfg<br />
define host{<br />
use                  linux-server<br />
host_name    labclient1<br />
alias                 labclient1<br />
address            192.168.0.163<br />
}</div>
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define hostgroup{<br />
hostgroup_name      labclient<br />
alias                            Linux Servers<br />
members                   labclient1<br />
}</div>
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define service{<br />
use                              local-service<br />
host_name                  labclient1<br />
service_description     PING<br />
check_command     check_ping!100.0,20%!500.0,60%<br />
}</div>
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<strong>(NOTE:change hostname as “labclient1” for rest of services as well)</strong></div>
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<strong>Now, edit ngios.cfg file and add entry for linux pc.</strong><br />
# vi /etc/nagios/nagios.cfg<br />
cfg_file=/etc/nagios/objects/linux.cfg<br />
:wq!</div>
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<strong>Verify configuration nagios configuration file for errors:</strong><br />
# nagios –v /etc/nagios/nagios.cfg</div>
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<strong>Run below command to check whether the nrpe service is working and its listening to client linux pc or not:</strong><br />
#/usr/lib/nagios/pulgins/check_nrpe –H 192.168.0.163</div>
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<strong>Start the following services on nagios server:</strong><br />
# service httpd start<br />
# service nagios start<br />
# service nrpe start<br />
Now, check the newly added linux pc on nagios monitoring tool.</div>
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<span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">Add Window machine to nagios server for monitoring:</span></h4>
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<strong>Install NSClient++ package on windows machine. Chose form 32bit or 64bit package.</strong><br />
http://nsclient.org/nscp/downloads</div>
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Once downloaded the package run the exe file and enter the allow host ip i.e. nagios server ip (192.168.0.150), NSClient password as “password “and also load the following modules as well:<br />
Enable common check plugins<br />
Enable NSClient server (check_nt)<br />
Enable nrpe server (check_nrpe)<br />
Enable WMI checks</div>
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<strong>Now start the NSClient++ service by:</strong><br />
Control Panel > Administrative Tools > services > NSClient++ > stop > start</div>
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<strong>If you want to do changes for NSClient then can edit “nsclient.ini” file to modify the settings whether its for ip address or for password etc.</strong><br />
C:\Program Files\NSClient++\nsclient.ini<br />
After make changes don’t forget to restart the NSClient service.</div>
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<strong>Now come to the nagios server and do the followings:</strong><br />
Come to nagios server (192.168.0.160) machine:<br />
# cd /etc/nagios/objects/<br />
# vim windows.cfg<br />
Open windows.cfg file and make entry for hostname, alias and ip of window pc.This to be done for host, hostgroup and services.<br />
define host{<br />
use windows-server ; Inherit default values from a template<br />
host_name admin1<br />
alias My Windows Server<br />
address 192.168.0.100 ; IP address of the host<br />
}</div>
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<strong>Now, check ngios.cfg file and make sure there should be entry for windows pc.</strong><br />
# vi /etc/nagios/nagios.cfg<br />
cfg_file=/etc/nagios/objects/windows.cfg<br />
: wq!</div>
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<strong>Verify configuration nagios configuration file for errors:</strong><br />
# nagios –v /etc/nagios/nagios.cfg</div>
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<strong>Run below command to check whether the nrpe service is working and its listening to client windows pc or not:</strong><br />
#/usr/lib/nagios/pulgins/check_nrpe –H 192.168.0.100</div>
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<strong>Start the following services on nagios server:</strong><br />
# service httpd start<br />
# service nagios start<br />
# service nrpe start<br />
Now, check the newly added windows pc on nagios monitoring tool.</div>
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Nagios Installation and Configuration on Centos:

What is Nagios ? Nagios is an Open Source monitoring tool, its provides you monitoring environment to keep an eye on your different m...

LinuxGateway

Nagios Installation and Configuration on Centos:

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