Scenario
In this tutorial i am going to use two systems as mentioned below.
Nagios server:
Operating system : CentOS 6.5 minimal installation IP Address : 192.168.1.101/24
Nagios client:
Operating System : Ubuntu 13.04 IP Address : 192.168.1.100/24
Prerequisites
Before
installing Nagios, make sure that you’ve a properly installed and
configured LAMP stack in your server. To install and configure LAMP
server, refer any one of the following links.
Also install the following prerequisites too. All commands should be run as root user.
# yum install gd gd-devel gcc glibc glibc-commonInstall Nagios
I tested this how-to on CentOS 6.5 minimal server, although it should work on all RHEL 6.x and its clones like CentOS 6.x and Scientific Linux 6.x.
Nagios will not be found in
CentOS official repositories, so let us add the EPEL repository to
install nagios. To add and enable EPEL repository :
First go to the EPEL repository download page. Download the latest EPEL rpm and install it as shown below.
For x86
# wget http://epel.mirror.net.in/epel/6/i386/epel-release-6-8.noarch.rpm
For x64
#wget http://epel.mirror.net.in/epel/6/x86_64/epel-release-6-8.noarch.rpm
# rpm -Uvh epel-release-6-8.noarch.rpm
Adding EPEL Repository to RHEL / CentOS / Scientific Linux 5.x
First go to the EPEL repository download page. Download the latest EPEL rpm and install it as shown below.
# wget http://epel.mirror.net.in/epel/5/i386/epel-release-5-4.noarch.rpm # rpm -Uvh epel-release-5-4.noarch.rpm
Now list out the installed repositories using command:
# yum repolist
Next install nagios with all plug-ins and nagios agents(nrpe-agent) using command:
# yum install nagios*
Note:
It worked for me either if i keep SELINUX and iptables enable or
disable. All you need to do is allow the apache port through iptables as
shown below.
# vi /etc/sysconfig/iptables
Add the following line:
[...] -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT [...]
Save and close the file. Restart iptables.
# service iptables restartConfigure Nagios
Add the admin mail address in the nagios contact file to receive alerts from nagios server. To do that edit file /etc/nagios/objects/contacts.cfg,
# vi /etc/nagios/objects/contacts.cfg
Find the following line and enter the email id:
[...] email sk@unixmen.com ; [...
Save and close the file. Then Edit file /etc/httpd/conf.d/nagios.conf,
# vi /etc/httpd/conf.d/nagios.conf
And
edit the following lines if you want to access nagios administrative
console from a particular IP series. Here i want to allow nagios
administrative access from 192.168.1.0/24 series only.
[...]
## Comment Lines 15 & 16 ##
# Order allow,deny
# Allow from all
## Uncomment and Change lines 17,18 & 19 as shown below ##
Order deny,allow
Deny from all
Allow from 127.0.0.1 192.168.1.0/24
[...]
Set nagiosadmin password
# htpasswd /etc/nagios/passwd nagiosadmin New password: Re-type new password: Updating password for user nagiosadmin
Start nagios and httpd services and let them to start automatically on every boot.
# service nagios start # service httpd start # chkconfig nagios on # chkconfig httpd on
Access Nagios admin console
Open nagios administrator console with URL http://nagios-server-ip/nagios and enter the username as nagiosadmin and its password which we created in the earlier steps.
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:
Like i said before, you have to add EPEL repository in your CentOS/RHEL/Scientific Linux 6.x clients to install nrpe package.
Install “nrpe” and “nagios-plugins” packages in client systems to be monitored.
# yum install nrpe nagios-plugins-all opensslOn Debian/Ubuntu clients:
$ sudo apt-get install nagios-nrpe-server nagios-pluginsConfigure Monitoring targets
Edit /etc/nagios/nrpe.cfg file,
# vi /etc/nagios/nrpe.cfgAdd your Nagios server ip address
[...]
## Line 81 - Add the Nagios server IP ##
allowed_hosts=127.0.0.1 192.168.1.101
[...]
## line around 215 add some plugin like mailq posfix
command[check_mailq]=/usr/lib/nagios/plugins/check_postfix_queue -w 300 -c 1000
Start nrpe service:
# 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 to add the clients to be monitored through nagios server. Edit “/etc/nagios/nagios.cfg” file,
# vi /etc/nagios/nagios.cfg
and uncomment the following lines.
## Line 52 - Uncomment ## cfg_dir=/etc/nagios/servers
Create a directory called “servers” under “/etc/nagios/”.
# mkdir /etc/nagios/servers
Create config file to the client to be monitored:
# vi /etc/nagios/servers/clients.cfg
define host{
use linux-server
host_name client
alias client
address 192.168.1.100 ## Client IP ##
max_check_attempts 5
check_period 24x7
notification_interval 30
notification_period 24x7
}
Finally restart nagios service.
# service nagios restart
Now open the nagios admin console in the browser and navigate to “Hosts”
section in the left pane. You will see the newly added client will be
visible there. Click on the host to see if there is anything wrong or
alerts.
Like this way, you can define more clients by creating a separate config files “/etc/nagios/servers directory for each client.
Define servicesWe did define the monitoring host before. Now let us add some services of the monitoring host. For example to monitor the ssh service, add the following lines shown in red colour in the /etc/nagios/servers/clients.cfg file.
# vi /etc/nagios/servers/clients.cfg
define host{
use linux-server
host_name client
alias client
address 192.168.1.100 ## Client IP ##
max_check_attempts 5
check_period 24x7
notification_interval 30
notification_period 24x7
}
define service {
use generic-service
host_name client
service_description SSH
check_command check_ssh
notifications_enabled 0
}
Save and close the file. Restart Nagios.# service nagios restartNow log in to Nagios web console and check for the added services. Navigate to Services section, you’ll see the ssh service there.
To know more about object definitions such as Host definitions, service definitions, contact definitions and more please do visit here. This page will describe you the description and format of all object definitions.
That’s all about now. Good Luck! Stay healthy!
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