Install Nagios Server Monitoring on Ubuntu

Nagios monitors your entire IT infrastructure to ensure systems, applications, services, and business processes are functioning properly. In the event of a failure, Nagios can alert technical staff of the problem, allowing them to begin remediation processes before outages affect business processes, end-users, or customers. With Nagios, you’ll never be left having to explain why an unseen infrastructure outage hurt your organization’s bottom line.

Nagios runs periodic checks on critical parameters of application, network and server resources. It can monitor, for example, memory usage, disk usage, microprocessor load, the number of currently running processes and log files. Nagios also can monitor services, such as Simple Mail Transfer Protocol (SMTP), Post Office Protocol 3 (POP3), Hypertext Transfer Protocol (HTTP) and other common network protocols. Active checks are initiated by Nagios, while passive checks come from external applications connected to the monitoring tool.

Install Nagios Server Monitoring on Ubuntu 16.04

[1] Install Apache2

 root@Pirates:~# apt-get -y install apache2

[2]Configure Apache2

Change ~ ServerTokens

 This directive configures what you return as the Server HTTP response Header. The default is 'Full' which sends information about the OS-Type and compiled in modules.

root@Pirates:~#  vi /etc/apache2/conf-enabled/security.conf

# line 25: change

ServerTokens Prod

root@Pirates:~#vi /etc/apache2/mods-enabled/dir.conf

# line 2: add file name that it can access only by directory's name
DirectoryIndex index.html index.htm

Press Esc Then save the file with :wq!

root@udhaya-raav:~# vi /etc/apache2/apache2.conf

# line 70: add to specify server name

ServerName www.nagios-pirates.com  (any name)

Press Esc Then save the file with :wq

root@Pirates:~#  vi /etc/apache2/sites-enabled/000-default.conf

# line 11: change to webmaster's email

ServerAdmin@gmail.com

After the changes in 000-default.conf Save the configuration.

Now restart your apache service through Terminal.

root@Pirates:~#service apache2 restart

Access to "HTTP://(your server's hostname or IP address)/" with web browser. It's OK if the following page is shown. (default page) 

[3]Install PHP & Configuration:

Install PHP,

root@Pirates:~# apt-get  install php php-cgi libapache2-mod-php php-common php-pear php-mbstring

Configure Apache2 to use PHP scripts.

root@Pirates:~# a2enconf php7.0-cgi

root@nagios:~#  vi /etc/php/7.0/apache2/php.ini

# line 924: uncomment and add your timezone
date.timezone = "Asia/Tokyo"

PressEsc button then  type :wq! 

root@Pirates:~# systemctl restart apache2.service

Create a PHP test page and access to it from any clients with the web browser. It's OK if the following page is shown.

root@nagios:~# vi /var/www/html/index.php

PressEsc button then  type :wq!

TEST PAGE :

 Now it's  Hero Time.Install Nagios and plugins from Ubuntu repo.

root@Pirates:~# apt-get -y install nagios3 nagios-plugins-basic

While installing, it will ask you to configure the password.Configure your own password.

EXTERNAL COMMAND OPTION

This option allows you to specify whether or not Nagios should check for external commands (in the command file defined below)

root@nagios:~# vi /etc/nagios3/nagios.cfg

# line 145: change        

check_external_commands=1

PressEsc button then  type :wq (For saving the file after mofify)

root@nagios:~# vi /etc/nagios3/apache2.conf

# line 40: change access permission

#Allow From All
 Allow From localhost 192.168.1.0/24

Instead of 192.168.1.0/24 config. your LAN network IP/Hole Subnet.

PressEsc button then  type :wq (For saving the file after mofify)

root@nagios:~#  vi /etc/nagios3/conf.d/localhost_nagios2.cfg

# line 22: comment out and add

# all partitions are monitored by default but it's unnecessary all,

# so change to specific partition to monitor (the example below specify root partition)

#check_command check_all_disks!20%!10%

check_command check_disk!20%!10%!/

PressEsc button then  type :wq (For saving the file after mofify)

root@nagios:~# chgrp -R www-data /var/lib/nagios3

root@nagios:~# chmod 750 /var/lib/nagios3/rw

root@nagios:~# systemctl restart nagios3.service apache2.service

Access to the "http://(Nagios server's hostname or IP address)/nagios3/" from a client which is in the network allowed by Nagios server and authenticate with the Nagios admin user "nagiosadmin" and password is newly configured one during installation.

After the sucessfull login, you will see Nagios admin panel.

Click that option of Tactical Overview then it will show All the notifications.

Click Host Groups option then you can see localhost server details.

 Credits: Udhaya Raav