Now that Nagios has been installed, it’s time to configure it. Sample configuration files have been installed in the /usr/local/nagios/etc directory. For the most part, the settings in the sample files should work fine for getting started with Nagios. You should, however change the e-mail address associated with the nagiosadmin contact definition to the address you’d like to use for receiving alerts. To do so, you change the email field in /usr/local/nagios/etc/objects/contacts.cfg with your favorite editor.
Next, install the Nagios web config file in the Apache conf.d directory:
Create a nagionsadmin account for logging into the Nagios web interface. Remember the password you assign to this account.
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Now restart Apache to make the new settings take effect.
Next, extract the Nagios plugins source code tarball:
tar xzf nagios-plugins-2.0.3.tar.gz
Compile and install the plugins:
./configure –with-nagios-user=nagios –with-nagios-group=nagios
Now configure nagios to automatically start when the system boots:
ln -s /etc/init.d/nagios /etc/rc5.d/599nagios
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:
You should now be able to access the Nagios web interface at the URL below. You’ll be promoted 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 to check all the services associated with your machine, as the checks are spread out over time.
If you want to receive e-mail notifications for Nagios 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 e-mail notification commands found in /usr/local/nagios/etc/objects/commands.cfg and change and /bin/mail references to /usr/bin/mail. Once you do that, you’ll need to restart Nagios to make the configuration changes live:
sudo /etc/init.d/nagios restart
In the next article, we’ll access Nagios via the web interface and configure it to work with pfSense.