This guide 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. No advanced installation options are discussed here - just the basics that will work for 95% of users who want to get started.
These instructions were written based on an Ubuntu 14.04 - Server installation. They should work with most recent vesrions of Ubuntu with minor changes on some versions.
If you follow these instructions, here's what you'll end up with:
Make sure you've installed the following packages on your Ubuntu installation before continuing.
You can use apt-get to install these packages by running the following commands:
sudo apt-get install apache2 libapache2-mod-php5 build-essential libgd-dev
Become the root user.
Create a new nagios user account and give it a password.
/usr/sbin/useradd -m -s /bin/bash nagios passwd nagios
You will need to also add a nagios group (if it's not created by default).
/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 -a -G nagcmd nagios /usr/sbin/usermod -a -G nagcmd www-data
Create a directory for storing the downloads.
mkdir ~/downloads cd ~/downloads
Download the source code tarballs of both Nagios Core and the Nagios plugins (visit https://www.nagios.org/download/ for links to the latest versions). These directions were tested with Nagios 4.2.1 and Nagios Plugins 2.1.3.
wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-4.2.1.tar.gz wget http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-2.1.3.tar.gz
Extract the Nagios Core source code tarball.
cd ~/downloads tar xzf nagios-4.2.1.tar.gz cd nagios-4.2.1
Run the Nagios configure script, passing the name of the group you created earlier like so:
Compile the Nagios Core source code.
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 Core yet - there's still more that needs to be done...
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 Core. 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.
Install the Nagios Core web config file in the Apache conf.d directory.
Create a nagiosadmin account for logging into the Nagios Core 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.
Note: Consider implementing the ehanced CGI security measures described here to ensure that your web authentication credentials are not compromised.
Extract the Nagios plugins source code tarball.
cd ~/downloads tar xzf nagios-plugins-2.1.3.tar.gz cd nagios-plugins-2.1.3
Compile and install the plugins.
./configure --with-nagios-user=nagios --with-nagios-group=nagios make make install
Configure Nagios Core to automatically start when the system boots.
ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios
Verify the sample Nagios Core configuration files.
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
If there are no errors, start Nagios Core.
You should now be able to access the Nagios Core web interface at the URL below. You'll be prompted for the username (nagiosadmin) and password you specified earlier.
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 Core to check all the services associated with your machine, as the checks are spread out over time.
If you want to receive email notifications for Nagios Core alerts, you need to install the mailx (Postfix) package.
sudo apt-get install mailx sudo apt-get install postfix
You'll have to edit the Nagios Core email notification commands found in /usr/local/nagios/etc/objects/commands.cfg and change any '/bin/mail' references to '/usr/bin/mail'. Once you do that you'll need to restart Nagios Core to make the configuration changes live.
sudo /etc/init.d/nagios restart
Configuring email notifications is outside the scope of this documentation. Refer to your system documentation, search the web, or look to the Nagios Support Portal or Nagios Community Wiki for specific instructions on configuring your Ubuntu system to send email messages to external addresses.
Congratulations! You sucessfully installed Nagios Core. Your journey into monitoring is just beginning. You'll no doubt want to monitor more than just your local machine, so check out the following docs ...