Nagios 4.4.1 on ubuntu 15.04 for Monitoring your Infrastructure part-2

In the 1st part I have configured the nagios  and it have started to monitor the instance locally now come on the other part.adding clients to it .

Add Monitoring targets to Nagios server

Now, let us add some clients to monitor by Nagios server.

To do that we have to install nrpe and nagios-plugins in our monitoring targets.

On CentOS/RHEL/Scientifc Linux clients:

Add EPEL repository in your CentOS/RHEL/Scientific Linux 6.x or 7 clients to install nrpe package.

To install EPEL on CentOS 7, run the following command:

yum install epel-release

On CentOS 6.x systems, refer the following link.

• Install EPEL Repository On CentOS 6.x

Install “nrpe” and “nagios-plugins” packages in client systems:

yum install nrpe nagios-plugins-all openssl

On Debian/Ubuntu clients:

sudo apt-get update

sudo apt-get install nagios-nrpe-server nagios-plugins

Configure Monitoring targets

Edit /etc/nagios/nrpe.cfg file,

sudo nano /etc/nagios/nrpe.cfg

Add your Nagios server ip address:

[...]
## Find the following line and add the Nagios server IP ##
allowed_hosts=127.0.0.1 192.168.1.104
[...]

Start nrpe service on CentOS clients:

CentOS 7:

systemctl start nrpe

chkconfig nrpe on

CentOS 6.x:

service nrpe start

chkconfig nrpe on

For Debian/Ubuntu Clients, start nrpe service as shown below:

sudo /etc/init.d/nagios-nrpe-server restart

Now, go back to your Nagios server, and add the clients ( in the configuration file.

To do that, Edit “/usr/local/nagios/etc/nagios.cfg” file,

sudo nano /usr/local/nagios/etc/nagios.cfg

and uncomment the following lines.

## Find and uncomment the following line ##
cfg_dir=/usr/local/nagios/etc/servers

Create a directory called “servers” under “/usr/local/nagios/etc/”. 

sudo mkdir -p /usr/local/nagios/etc/servers

Copy the localhost.cfg to the server directory with the client name you want i have use cl1

sudo cp  -ar /usr/local/nagios/etc/objects/localhost.cfg \ /usr/local/nagios/etc/servers/cl1.cfg

Create a file called groups.cfg in side of  /usr/local/nagios/etc/servers/ directory 
Add a definition of new group for client or in the groups file add the following lines
(if you are really new with Nagios)

###############################################################################
###############################################################################
#
# HOST GROUP DEFINITION
#
###############################################################################
###############################################################################

# Define an optional hostgroup for Linux machines

define hostgroup{
        hostgroup_name  linux-server ; The name of the hostgroup
        alias           Linux Server ; Long name of the group
        members         cl1     ; Comma separated list of hosts that belong to this group
        }

After this save and close the file and lets go to the cl1.cfg file.
change the host ip for me it was 192.168.100.4 it may me some thing else for you.

define host{
        use                     linux-server            ; Name of host template to use
                                                        ; This host definition will inherit all variables that are defined
                                                        ; in (or inherited by) the linux-server host template definition.
        host_name               cl1
        alias                   cl1.centos.lan
        address                 192.168.100.4
        }

change only which are in bold only. and then remove the section of hot group from the file or you can comment it out. after that seatch for localhost in the file and replace it with your value of host_name in my case its cl1  and save and close the file. if you are not able to do it then fire the below command and it will tale care of the rest for you.

sed -i 's/localhost/cl1/g' /usr/local/nagios/etc/servers/cl1.cfg

it will replace all the occurances of localhost with cl1. and we are almost done.

 fire this command and check if you have done any configuration error

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

  and We are done we have successfully added a client to our nagisos. just dont forget ot restart your nagios with also add the required rule in iptables or you can face some issue with it am sure you can manage this 

sudo systemctl restart nagios

login on your web interface.We have successfully added our first client to nagios for monitoring

Gyus enjoy I will also wotking on PNP4nagios will explain you in the next part how you can have some cool graph of the system performance generated using nagios.