Nagios Tutorial

Nagios is the most popular continuous monitoring tool. It monitors complete IT infrastructure including its systems, applications, services processes etc.

This tutorial gives an overview of Nagios and lets learners start their journey with Nagios.

The tutorial is written with an assumption that the learner is comfortable working with Ubuntu System 16.04/18.04, and basic packages like gcc compiler, build essential, apache, php and root/sudo access.

If you are new to any of these concepts, we suggest you pick up tutorials related to these concepts. You can also consider choosing Linux and Ubuntu tutorials for a better understanding.

DevOps lifecycle is a continuous loop of several stages, continuous monitoring is the last stage of this loop. Continuous monitoring is one of the stages in this lifecycle. In this chapter, let us learn in detail about what continuous monitoring is and how Nagios is helpful for this purpose.

What is Continuous Monitoring

Continuous monitoring starts when the deployment is done on the production servers. From then on, this stage is responsible to monitor everything happening. This stage is very crucial for the business productivity.

There are several benefits of using Continuous monitoring −

• It detects all the server and network problems.
• It finds the root cause of the failure.
• It helps in reducing the maintenance cost.
• It helps in troubleshooting the performance issues.
• It helps in updating infrastructure before it gets outdated.
• It can fix problems automatically when detected.
• It makes sure the servers, services, applications, and network are always up and running.
• It monitors complete infrastructure every second.

What is Nagios

Nagios is an open source continuous monitoring tool which monitors network applications and servers. It can find and repair problems detected in the infrastructure, and stop future issues before they affect the end users. It gives the complete status of your IT infrastructure and its performance.

Why Nagios

Nagios offers the following features making it usable by a large group of user community −

• It can monitor Database servers such as SQL Server, Oracle, Mysql, Postgres
• It gives application level information (Apache, Postfix, LDAP, Citrix etc.).
• Provides active development.
• Has excellent support from a huge active community.
• Nagios runs on any operating system.
• It can ping to see if the host is reachable.

Benefits of Nagios

Nagios offers the following benefits for the users −

• It helps in getting rid of periodic testing.
• It detects split-second failures when the wrist strap is still in the “intermittent” stage.
• It reduces maintenance cost without sacrificing performance.
• It provides timely notification to the management of control and breakdown.

Nagios Architecture

The following points are worth notable about Nagios architecture −

• Nagios has server-agent architecture.
• Nagios server is installed on the host and plugins are installed on the remote hosts/servers which are to be monitored.
• Nagios sends a signal through a process scheduler to run the plugins on the local/remote hosts/servers.
• Plugins collect the data (CPU usage, memory usage etc.) and send it back to the scheduler.
• Then the process schedules send the notifications to the admin/s and update Nagios GUI.

The following figure shows Nagios Server Agent Architecture in detail −

Nagios XI

It provides monitoring for complete IT infrastructure components like applications, services, network, operating systems etc. It gives a complete view of your infrastructure and business processes. The GUI is easily customizable giving the used flexibility. The standard edition of this tool costs $1995 and enterprise edition costs $3495.

Nagios Core

It is the core of monitoring IT infrastructure. Nagios XI product is also fundamentally based on Nagios core. Whenever there is any issue of failure in the infrastructure, it sends an alert/notification to the admin who can take the action quickly to resolve the issue. This tool is absolutely free.

Nagios Log Server

It makes searching for log data very simple and easy. It keeps all the log data at one location with high availability setup. It can easily send alerts if any issue is found in the log data. It can scale to 1000s of severs giving more power, speed, storage, and reliability to your log analysis platform. The price of this tool depends on the number of instances – 1 Instance $3995, 2 Instances $4995, 3 Instances $5995, 4 Instances $6995, 10 Instances $14995.

Nagios Fusion

This product provides a centralized view of the complete monitoring system. With Nagios Fusion, you can set up separate monitoring servers for separate geographies. It can be easily integrated with Nagios XI and Nagios core to give the complete visibility of the infrastructure. This tool costs $2495.

Nagios Network Analyser

It gives the complete information of the network infrastructure to the admin with the potential threats on the network so that admin can take quick actions. It shares very detailed data about the network after in-depth network analysis. This tool costs $1995.

Nagios XI

It provides monitoring for complete IT infrastructure components like applications, services, network, operating systems etc. It gives a complete view of your infrastructure and business processes. The GUI is easily customizable giving the used flexibility. The standard edition of this tool costs $1995 and enterprise edition costs $3495.

Nagios Core

It is the core of monitoring IT infrastructure. Nagios XI product is also fundamentally based on Nagios core. Whenever there is any issue of failure in the infrastructure, it sends an alert/notification to the admin who can take the action quickly to resolve the issue. This tool is absolutely free.

Nagios Log Server

It makes searching for log data very simple and easy. It keeps all the log data at one location with high availability setup. It can easily send alerts if any issue is found in the log data. It can scale to 1000s of severs giving more power, speed, storage, and reliability to your log analysis platform. The price of this tool depends on the number of instances – 1 Instance $3995, 2 Instances $4995, 3 Instances $5995, 4 Instances $6995, 10 Instances $14995.

Nagios Fusion

This product provides a centralized view of the complete monitoring system. With Nagios Fusion, you can set up separate monitoring servers for separate geographies. It can be easily integrated with Nagios XI and Nagios core to give the complete visibility of the infrastructure. This tool costs $2495.

Nagios Network Analyser

It gives the complete information of the network infrastructure to the admin with the potential threats on the network so that admin can take quick actions. It shares very detailed data about the network after in-depth network analysis. This tool costs $1995.

In this chapter, the steps to set up Nagios on Ubuntu are discussed in detail.

Before you install Nagios, some packages such as Apache, PHP, building packages etc., are required to be present on your Ubuntu system. Hence, let us install them first.

Step 1 − Run the following command to install pre-required packages −

sudo apt-get install wget build-essential apache2 php apache2-mod-php7.0 php-gd

libgd-dev sendmail unzip

Step 2 − Next, create a user and group for Nagios and add them to Apache www-data user.

sudo useradd nagios

sudo groupadd nagcmd

sudo usermod -a -G nagcmd nagios

sudo usermod -a -G nagios,nagcmd www-data

Step 3 − Download the latest Nagios package.

wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-

4.4.3.tar.gz

Step 4 − Extract the tarball file.

tar -xzf nagios-4.4.3.tar.gz

cd nagios-4.4.3/

Step 5 − Run the following command to compile Nagios from source.

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

Step 6 − Run the following command to build Nagios files.

make all

Step 7 − Run the command shown below to install all the Nagios files.

sudo make install

Step 8 − Run the following commands to install init and external command configuration files.

sudo make install-commandmode

sudo make install-init

sudo make install-config

sudo /usr/bin/install -c -m 644 sample-config/httpd.conf /etc/apache2/sitesavailable/

nagios.conf

Step 9 − Now copy the event handler directory to Nagios directory.

sudo cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/

sudo chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers

Step 10 − Download and extract Nagios plugins.

cd

wget https://nagios-plugins.org/download/nagiosplugins-

2.2.1.tar.gz

tar -xzf nagios-plugins*.tar.gz

cd nagios-plugins-2.2.1/

Step 11 − Install Nagios plugins using the below command.

./configure –with-nagios-user=nagios –with-nagios-group=nagios –with-openssl

make

sudo make install

Step 12 − Now edit the Nagios configuration file and uncomment line number 51 → cfg_dir=/usr/local/nagios/etc/servers

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

Step 13 − Now, create a server directory.

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

Step 14 − Edit contacts configuration file.

sudo gedit /usr/local/nagios/etc/objects/contacts.cfg

Step 15 − Now enable the Apache modules and configure a user nagiosadmin.

sudo a2enmod rewrite

sudo a2enmod cgi

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

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

Step 16 − Now, restart Apache and Nagios.

service apache2 restart

service nagios start

cd /etc/init.d/

sudo cp /etc/init.d/skeleton /etc/init.d/Nagios

Step 17 − Edit the Nagios file.

sudo gedit /etc/init.d/Nagios

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

Step 18 − Make the Nagios file executable and start Nagios.

sudo chmod +x /etc/init.d/nagios

service apache2 restart

service nagios start

Step 19 − Now go to your browser and open url → http://localhost/nagios. Now login to Nagios with username nagiosadmin and use the password which you had set earlier. The login screen of Nagios is as shown in the screenshot given below −

If you have followed all the steps correctly, Nagios web interface will show up. You can find the Nagios dashboard as shown below −