Nagios Network Monitoring System Setup in Ubuntu

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Nagios is a host and service monitor designed to inform you of network problems before your clients, end-users or managers do. It has been designed to run under the Linux operating system, but works fine under most *NIX variants as well. The monitoring daemon runs intermittent checks on hosts and services you specify using external "plugins" which return status information to Nagios. When problems are encountered, the daemon can send notifications out to administrative contacts in a variety of different ways (email, instant message, SMS, etc.). Current status information, historical logs, and reports can all be accessed via a web browser.

WARNING: "this tutorial is meant for users that have a good knowledge of development tools and manual installation process and will be hardly supported by the Ubuntu community. Standard supported procedure are to install packages from the official repositories, not to compile them by hand".

Install Nagios in Ubuntu

This Tutorial is intended to provide you with simple instructions on how to install Nagios from source (code) on Ubuntu and have it monitoring your local machine inside of 20 minutes.

If you follow these instructions, here's what you'll end up with:

Nagios and the plugins will be installed underneath /usr/local/nagios

Nagios will be configured to monitor a few aspects of your local system (CPU load, disk usage, etc.)

The Nagios web interface will be accessible at http://localhost/nagios/

Required Packages

Make sure you've installed the following packages on your Ubuntu installation before continuing.

Apache 2
GCC compiler and development libraries
GD development libraries

Preparing Your System

First you need to install the following packages

sudo apt-get install apache2

sudo apt-get install build-essential

sudo apt-get install libgd2-xpm-dev

1) Create Account Information

Become the root user.

sudo -s

Create a new nagios user account and give it a password.

#/usr/sbin/useradd nagios

#passwd nagios

On Ubuntu server edition , you will need to also add a nagios group (it's not created by default). You should be able to skip this step on desktop editions of Ubuntu.

#/usr/sbin/groupadd nagios

#/usr/sbin/usermod -G nagios nagios

Create a new nagcmd group for allowing external commands to be submitted through the web interface. Add both the nagios user and the apache user to the group.

#/usr/sbin/groupadd nagcmd

#/usr/sbin/usermod -G nagcmd nagios

#/usr/sbin/usermod -G nagcmd www-data

2) Download Nagios and the Plugins

Create a directory for storing the downloads.

#mkdir ~/downloads

#cd ~/downloads

Download the source code tarballs of both Nagios and the Nagios plugins (visit http://www.nagios.org/download/ for links to the latest versions). At the time of writing, the latest versions of Nagios and the Nagios plugins were 2.10 and 1.4.10, respectively.

#wget http://switch.dl.sourceforge.net/sourceforge/nagios/nagios-2.10.tar.gz

#wget http://kent.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.10.tar.gz

3) Compile and Install Nagios

Extract the Nagios source code tarball.

#cd ~/downloads

#tar xzf nagios-2.10.tar.gz

#cd nagios-2.10

Run the Nagios configure script, passing the name of the group you created earlier like so:

#./configure --with-command-group=nagcmd

Compile the Nagios source code.

#make all

Install binaries, init script, sample config files and set permissions on the external command directory.

#make install

#make install-init

#make install-config

#make install-commandmode

Don't start Nagios yet -- there's still more that needs to be done...

4) Customize Configuration

Sample configuration files have now been installed in the /usr/local/nagios/etc directory. These sample files should work fine for getting started with Nagios. You'll need to make just one change before you proceed...

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.

#vi /usr/local/nagios/etc/objects/contacts.cfg

5) Configure the Web Interface

Install the Nagios web config file in the Apache conf.d directory.

#make install-webconf

Create a nagiosadmin account for logging into the Nagios web interface. Remember the password you assign to this account -- you'll need it later.

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

Restart Apache to make the new settings take effect.

#/etc/init.d/apache2 reload

6) Compile and Install the Nagios Plugins

Extract the Nagios plugins source code tarball.

#cd ~/downloads

#tar xzf nagios-plugins-1.4.10.tar.gz

#cd nagios-plugins-1.4.10

Compile and install the plugins.

#./configure --with-nagios-user=nagios --with-nagios-group=nagios

#make

#make install

7) Start Nagios

Configure Nagios to automatically start when the system boots.

#ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios

Verify the sample Nagios configuration files.

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

If there are no errors, start Nagios.

#/etc/init.d/nagios start

8) Login to the Web Interface

You should now be able to access the Nagios web interface at the URL below. You'll be prompted for the username (nagiosadmin) and password you specified earlier.

http://localhost/nagios/

Click on the "Service Detail" navbar link to see details of what's being monitored on your local machine. It will take a few minutes for Nagios to check all the services associated with your machine, as the checks are spread out over time.

9) Other Modifications

If you want to receive email notifications for Nagios alerts, you need to install the mailx (Postfix) package.

#apt-get install mailx

You'll have to edit the Nagios email notification commands found in /usr/local/nagios/etc/commands.cfg and change any ‘/bin/mail' references to ‘/usr/bin/mail'. Once you do that you'll need to restart Nagios to make the configuration changes live.

#/etc/init.d/nagios restart

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