NAGIOS 4.2.0 SERVER/CLIENT CONFIGURATION IN CENTOS

Nagios is a best server monitoring software on the market. Server monitoring is made easy in Nagios because of the flexibility to monitor your servers with both agent-based and agentless monitoring.In this article we will explain about configuring nagios server and host which we will monitor.

Install the required packages
#yum install -y httpd php gcc glibc glibc-common gd gd-devel make net-snmp unzip

Create a new nagios user and nagcmd group account and set a password.
# useradd nagios
# groupadd nagcmd
add both the nagios user and the apache user to the nagcmd group.
# usermod -G nagios Nagios
# usermod -G nagios apache

Download Nagios Core 4.2.0 and Nagios Plugin 2.1.2
#mkdir /root/nagios
#cd /root/Nagios

Now download latest Nagios Core 4.2.0 and Nagios plugins 2.1.2 packages with wget command.
# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-4.2.0.tar.gz
# wget https://www.nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz

Extract the downloaded files
# tar -xvf nagios-4.2.0.tar.gz
# tar -xvf nagios-plugins-2.1.2.tar.gz

Configure Nagios Core
# cd nagios-4.2.0
# ./configure --with-command-group=nagios
# make all
# make install
# make install-init
# make install-commandmode
# make install-config

Customizing Nagios Configuration
#vi /usr/local/nagios/etc/objects/contacts.cfg

--------------------------------------------------------------------------

###############################################################################

# CONTACTS

###############################################################################

# Just one contact defined by default - the Nagios admin (that's you)

# This contact definition inherits a lot of default values from the 'generic-contact'

# template which is defined elsewhere.

define contact{

contact_name nagiosadmin ; Short name of user

use generic-contact ; Inherit default values from generic-contact template (defined above)

alias Nagios Admin ; Full name of user

email arunm8489@gmail.com ; *** CHANGE THIS TO YOUR EMAIL ADDRESS ****

}

-------------------------------------------------------------------------

We have to give our mailid to receive alerts here.

The below command will Configure Web interface for Nagios and a web admin user will be created “nagiosadmin”

#make install-webconf

In this step, we will be creating a password for “nagiosadmin”. After executing this command, please provide a password twice and keep it remember because this password will be used when you login in the Nagios Web interface.

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

#service httpd start

Compile and Install Nagios Plugin

#cd /root/Nagios

#cd nagios-plugins-2.1.2/

#./configure --with-nagios-user=nagios --with-nagios-group=Nagios

# make

# make install

Verify Nagios Configuration Files

#/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Sample output:
---------------------------------------------------------------------------

Nagios Core 4.2.0

Last Modified: 08-01-2016

License: GPL

Website: https://www.nagios.org

Reading configuration data...

Read main config file okay...

Read object config files okay...

Running pre-flight check on configuration data...

Checking objects...

Checked 8 services.

Checked 1 hosts.

Checked 1 host groups.

Checked 0 service groups.

Checked 1 contacts.

Checked 1 contact groups.

Checked 24 commands.

Checked 5 time periods.

Checked 0 host escalations.

Checked 0 service escalations.

Checking for circular paths...

Checked 1 hosts

Checked 0 service dependencies

Checked 0 host dependencies

Checked 5 timeperiods

Checking global event handlers...

Checking obsessive compulsive processor commands...

Checking misc settings...

Total Warnings: 0

Total Errors: 0

Things look okay - No serious problems were detected during the pre-flight check
----------------------------------------------------------------------------

# systemctl restart httpd

#systemctl enable httpd

#systemctl start Nagios

#systemctl enable Nagios

open it in your browser with “http://Your-server-IP-address/nagios”

Now we have to configure a host which we will monitor using our nagios server:

First install epel-release package to get required packages

#yum install epel-release

Install required packages

# yum install nrpe nagios-plugins-all openssl

# vi /etc/nagios/nrpe.cfg

Here add your Nagios server ip address

---------------------------------------------------------------------------------------

[...]

## Line 81 - Add the Nagios server IP ##

allowed_hosts=127.0.0.1 192.168.2.1

[...]
---------------------------------------------------------------------------------------

Now start nrpe service

#service nrpe start

# chkconfig nrpe on

Now go back to your Nagios server to add the clients to be monitored through nagios server. Edit “/usr/local/etc/nagios/nagios.cfg” file,

# vi /usr/local/nagios/etc/nagios.cfg

and uncomment the following lines.

## Line 52 - Uncomment ##

cfg_dir=/usr/local/etc/nagios/servers

Create a server directory

# mkdir /usr/local/etc/nagios/servers

# vi /usr/local/etc/nagios/servers/clients.cfg
---------------------------------------------------------------------------------------

define host{

use linux-server

host_name client

alias client

#mention the ip of host which we want to monitor

address 192.168.2.2

max_check_attempts 5

check_period 24x7

notification_interval 30

notification_period 24x7

}

--------------------------------------------------------------------------

Restart nagios service

#service nagios restart

go server space

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NAGIOS 4.2.0 SERVER/CLIENT CONFIGURATION IN CENTOS