It is quite possible to run Nagios3’s web interface directly from Nginx and a FastCGI server, rather than having to involve a web application server like Apache. This is useful if you want to preserve memory on your machine, for example.

First of all, we ask Nginx to serve the static files for the Nagios web interface. In Debian/Ubuntu, these live in /usr/share/nagios3/htdocs and /usr/share/nagios3/stylesheets, which is a little awkward, but just the sort of thing that the rewrite command is for …

location / {
root /usr/share/nagios3/htdocs;
index index.html;

rewrite ^/nagios3/stylesheets/(.*)$ /../stylesheets/$1 break;
rewrite ^/nagios3/(.*)$ /$1 break;
}

Next, we tell Nginx to send requests for CGI pages down to a FastCGI server :-

location ~ \.cgi$ {
root /usr/lib/cgi-bin/nagios3;
include /etc/nginx/fastcgi_params;

rewrite ^/cgi-bin/nagios3/(.*)$ /$1;

auth_basic "Nagios";
auth_basic_user_file /etc/nagios3/htpasswd.users;

fastcgi_pass 127.0.1.1:8998;
fastcgi_param SCRIPT_FILENAME /usr/lib/cgi-bin/nagios3$fastcgi_script_name;
fastcgi_param AUTH_USER $remote_user;
fastcgi_param REMOTE_USER $remote_user;
}

We need to make sure that these requests are under authentication, and that we pass the authenticated username to the CGI script properly, hence the auth_basic and fastcgi_param AUTH_USER lines.

That’s Nginx taken care of, but we also need to make sure there’s a generic FastCGI server running on the specified address/port. No configuration is necessary, as we’re passing everything we need, including the script name. fcgiwrap comes recommended on the Nginx wiki.

/usr/bin/spawn-fcgi -a 127.0.1.1 -p 8998 \
-u www-data -g www-data \
-f /usr/local/bin/fcgiwrap -P /var/run/fcgiwrap.pid

And that’s all you need!