How To Install Nagios on Ubuntu 18.04 LTS

Install Nagios on Ubuntu 18.04 LTS

In this tutorial, we will show you how to install Nagios on Ubuntu 18.04 LTS. For those of you who didn’t know, Nagios is open-source software that can be used for network and infrastructure monitoring. Nagios will monitor servers, switches, applications, and services. It alerts the System Administrator when something went wrong and also alerts back when the issues have been rectified. Resources that can be monitored include CPU, memory, and disk space loads, log files, temperature, or hardware errors. It can monitor various parameters and problems for services like HTTP, SMTP, DNS, and with the help of plugins, it can be highly extended. Nagios core was originally designed to run under Linux, although it should work under most other units as well.

This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you through the step-by-step installation of Nagios on a Ubuntu 18.04 (Bionic Beaver) server.

Install Nagios on Ubuntu 18.04 LTS Bionic Beaver

Step 1. First, make sure that all your system packages are up-to-date by running the following apt-get commands in the terminal.

sudo apt-get update
sudo apt-get upgrade

Step 2. Install LAMP (Linux, Apache, MariaDB, and PHP) server.

A Ubuntu 18.04 LAMP server is required. If you do not have LAMP installed, you can follow our guide here. Also, install all required PHP modules:

apt-get install php7.1-cli php7.1-mbstring php7.1-gd php7.1-opcache php7.1-mysql php7.1-json php7.1-mcrypt php7.1-xml php7.1-curl

Step 3. Create users and groups for Nagios.

For security reasons, create a user and group specifically to run Nagios:

useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd www-data

Step 4. Installing Nagios and plugins on Ubuntu 18.04 LTS.

The first thing to do is to go to Nagios’s download page and download the latest stable version of Nagios, At the moment of writing this article it is version 4.4.6:

wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.6.tar.gz
tar -zxvf /tmp/nagios-4.4.6.tar.gz
cd /tmp/nagios-4.4.6/

Perform the below steps to compile the Nagios from the source code:

./configure --with-nagios-group=nagios --with-command-group=nagcmd --with-httpd_conf=/etc/apache2/sites-enabled/
make all
make install
make install-init
make install-config
make install-commandmode
make install-webconf

Next steps, Download the latest nagios-plugins source and install using the following commands:

wget http://www.nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
tar xzf nagios-plugins-2.1.1.tar.gz
cd nagios-plugins-2.1.1
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install

Step 5. Configure Nagios on Ubuntu 18.04 Bionic Beaver.

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favorite editor and change the email address associated with the nagiosadmin contact definition to the address you’d like to use for receiving alerts.

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

Change the email address field to receive the notification:

[...]
define contact{
contact_name nagiosadmin ; Short name of userus
generic-contact ; Inherit default values from generic-contact template (defined above)
alias Nagios Admin ; Full name of useremail
[email protected] ; <<=== CHANGE THIS TO YOUR EMAIL ADDRESS ===
[...]

Step 6. Configure Apache web server for Nagios.

Now create Nagios apache2 configuration file:

nano /etc/apache2/sites-enabled/nagios.conf

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 the following lines ##
#   Order allow,deny
#   Allow from all

## Uncomment and Change lines as shown below ##
Order deny,allow
Deny from all
Allow from 127.0.0.1 192.168.1.0/24
[...]

Enable Apache’s rewrite and cgi modules:

sudo a2enmod rewrite
sudo a2enmod cgi

Configure Apache authentication:

We need to set up the password for the user nagiosadmin. This username will be used to access the web interface so it is important to remember the password that you will input here. Set the password running the following command and enter the password twice:

# sudo htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
New password:
Re-type new password:
Adding password for user nagiosadmin

Restart Apache for the changes to take effect:

systemctl restart apache2

Step 7. Verify and Start Nagios service.

Next, we have to make Nagios start at boot time, so first verify that the configuration file has no errors running the following command:

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

And you should get the output:

[...]
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
[...]

Ubuntu 18.04 uses systemd for starting/stopping all the services, so, we need to create Nagios.service file:

nano /etc/systemd/system/nagios.service

Add the following lines:

[Unit]
Description=Nagios
BindTo=network.target

[Install]
WantedBy=multi-user.target

[Service]
User=nagios
Group=nagios
Type=simple
ExecStart=/usr/local/nagios/bin/nagios /usr/local/nagios/etc/nagios.cfg

Enable Nagios to start automatically at system startup:

systemctl enable /etc/systemd/system/nagios.service

Now, start Nagios service:

systemctl start nagios

Step 8. Accessing Nagios.

Nagios will be available on HTTP port 80 by default. Open your favorite browser and navigate to http://your-domain.com/nagios or http://server-ip/nagios and complete the required steps to finish the installation. When prompted for username and password you will introduce the username “nagiosadmin” and the password that you entered in step 6.

Install Nagios on Ubuntu 18.04 LTS

Congratulations! You have successfully installed Nagios. Thanks for using this tutorial for installing the Nagios monitoring tool in ubuntu 18.04 (Bionic Beaver) systems. For additional help or useful information, we recommend you to check the official Nagios website.

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