How to Install Nagios 4.0.8 on Ubuntu 15.04 (Vivid Vervet)

Nagios is an open source software for system and network monitoring. Nagios can see the activity of a host and its services, and provides a warning/alert if something bad happens on the server. Nagios can run on Linux operating systems. At this time we are using Ubuntu 15.04 for the installation.

Prerequisites

  • Ubuntu 15.04 – 64bit
  • Root/Sudo access

What we will do in this tutorial:

  1. Installing package is needed – LAMP etc.
  2. User and group configuration
  3. Installing Nagios
  4. Configuring Apache
  5. Testing Nagios Server
  6. Adding a Host to Monitor

Installing package

Nagios requires gcc / build-essential for the compilation, LAMP (Apache, PHP, MySQL) for Nagios web base and Sendmail to send alerts from the server. To install all those packages and some additional packages:

apt-get install apache2 libapache2-mod-php5 build-essential libgd2-xpm-dev libssl-dev sendmail-bin sendmail heirloom-mailx wget apache2-utils curl daemon apt-file libnet-snmp-perl libpq5 libsensors4 libsnmp-base libtalloc2 libtdb1 libwbclient0 samba-common samba-common-bin smbclient snmp whois mrtg libcgi-pm-perl librrds-perl libgd-gd2-perl libmysqlclient-dev libperl5.20 libmysqlclient18 libradiusclient-ng2

User and group configuration

For Nagios to run, you have to create a new user for Nagios. We will name the user “nagios” and additionally create a group named “nagcmd”. Now we add the new user to the group as shown below:

useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios

Add a user and group for Nagios

Installing Nagios

Step 1 – Download and extract

cd ~
wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-4.0.8.tar.gz
tar -xzf nagios*.tar.gz
cd nagios-4.0.8/

Step 2 – Compile Nagios

Before you build Nagios, you need to configure it with the user and the group you have created earlier.

./configure –with-nagios-group=nagios –with-command-group=nagcmd

For more information please use: ./configure –help .

Now to install Nagios:

make all
sudo make install
sudo make install-commandmode
sudo make install-init
sudo make install-config
/usr/bin/install -c -m 644 sample-config/httpd.conf
/etc/apache2/sites-available/nagios.conf

Step 3 – Installing Nagios Plugin

Download and extract the nagios plugin:

cd ~
wget http://nagios-plugins.org/download/nagios-plugins-2.0.3.tar.gz
tar -xzf nagios-plugins*.tar.gz
cd nagios-plugin*/

Please do as above:

./configure –with-nagios-user=nagios –with-nagios-group=nagios –with-openssl
make && make install

Step 4 – Configure Nagios

After the installation phase is complete, you can find the default configuration of Nagios in /usr/local/nagios/.

Now to configure nagios contact with your email.

vim /usr/local/nagios/etc/nagios.cfg

Uncomment the line cfg_dir=/usr/local/nagios/etc/servers

Shows the line to uncomment

and add a new folder named servers:

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

The Nagios contact can be configured in the contact.cfg file. To open it use:

vim /usr/local/nagios/etc/objects/contacts.cfg

Then replace the default email with your own email.

Configuring Apache

Step 1 – enable Apache modules

sudo a2enmod rewrite
sudo a2enmod cgi

You can use htpasswd to configure a user nagiosadmin for the nagios web interface

sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

and type your password.

Step 2 – enable Nagios virtualhost

sudo ln -s /etc/apache2/sites-available/nagios.conf /etc/apache2/sites-enabled/

Step 3 – Start Apache and Nagios

/etc/init.d/apache2 restart
/etc/init.d/nagios start

When Nagios starts, you may see the following error :

Starting nagios (via systemctl): nagios.serviceFailed

And this is how to fix it:

cd /etc/init.d/
cp /etc/init.d/skeleton /etc/init.d/nagios

Now edit the Nagios file:

vim /etc/init.d/nagios

… and add the following code:

DESC="Nagios"
NAME=nagios
DAEMON=/usr/local/nagios/bin/$ NAME
DAEMON_ARGS="-d /usr/local/nagios/etc/nagios.cfg"
PIDFILE=/usr/local/nagios/var/$ NAME.lock

Make it executable and start Nagios:

chmod +x /etc/init.d/nagios
/etc/init.d/apache2 restart
/etc/init.d/nagios start

Testing the Nagios Server

Please open your browser and access the Nagios server ip that has been installed. http://192.168.1.101/nagios.

Adding a Host to Monitor

In this tutorial you will add an Ubuntu host to monitor to the Nagios server we have made above.

Nagios Server IP : 192.168.1.101
Ubuntu Host IP : 192.168.1.102

Step 1 – Connect to ubuntu host

ssh [email protected]

Step 2 – Install NRPE Service

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

Step 3 – Configure NRPE

After the installation is complete, edit the nrpe file /etc/nagios/nrpe.cfg:

vim /etc/nagios/nrpe.cfg

… and add Nagios Server IP 192.168.1.101 to the server_address.

Step 4 – Restart NRPE

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

Step 5 – Add Ubuntu Host to Nagios Server

Please connect to the Nagios server:

ssh [email protected]

Then create a new file for the host configuration in /usr/local/nagios/etc/servers/.

vim /usr/local/nagios/etc/servers/ubuntu_host.cfg

Add the following lines:

# Ubuntu Host configuration file
 
 define host {
         use                          linux-server
         host_name                    ubuntu_host
         alias                        Ubuntu Host
         address                      192.168.1.102 #Ubuntu host IP
         register                     1
 }
 
 define service {
       host_name                       ubuntu_host
       service_description             PING
       check_command                   check_ping!100.0,20%!500.0,60%
       max_check_attempts              2
       check_interval                  2
       retry_interval                  2
       check_period                    24x7
       check_freshness                 1
       contact_groups                  admins
       notification_interval           2
       notification_period             24x7
       notifications_enabled           1
       register                        1
 }
 
 define service {
       host_name                       ubuntu_host
       service_description             Check Users
       check_command		      check_local_users!20!50
       max_check_attempts              2
       check_interval                  2
       retry_interval                  2
       check_period                    24x7
       check_freshness                 1
       contact_groups                  admins
       notification_interval           2
       notification_period             24x7
       notifications_enabled           1
       register                        1
 }
 
 define service {
       host_name                       ubuntu_host
       service_description             Local Disk
       check_command                   check_local_disk!20%!10%!/
       max_check_attempts              2
       check_interval                  2
       retry_interval                  2
       check_period                    24x7
       check_freshness                 1
       contact_groups                  admins
       notification_interval           2
       notification_period             24x7
       notifications_enabled           1
       register                        1
 }
 
 define service {
       host_name                       ubuntu_host
       service_description             Check SSH
       check_command                   check_ssh
       max_check_attempts              2
       check_interval                  2
       retry_interval                  2
       check_period                    24x7
       check_freshness                 1
       contact_groups                  admins
       notification_interval           2
       notification_period             24x7
       notifications_enabled           1
       register                        1
 }

You can find many check_command in /usr/local/nagios/etc/objects/commands.cfg file. See there if you want to add more services like DHCP, POP etc.

And now check the configuration:

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

… to see if the configuration is correct.

Step 6 – Restart all services

On the Ubuntu Host start NRPE Service:

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

… and on the Nagios server, start Apache and Nagios:

/etc/init.d/apache2 restart
/etc/init.d/nagios restart

Step 7 – Testing Ubuntu Host

Open the Nagios server from the browser and see the ubuntu_host being monitored.

Conclusion

Nagios is an open source application for monitoring a system. Nagios has been widely used because of the ease of configuration. Nagios in support by various plugins, and you can even create your own plugins. Look here for more informations.

 

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