Understanding NGINX Configuration Files

When dealing with NGINX, one of the most crucial aspects to grasp is its configuration structure. The NGINX configuration files dictate how NGINX behaves, routing web requests, managing reverse proxies and likewise. Therefore, having a thorough understanding of how these files are organized and set up can aid in troubleshooting and optimizing your web server.

The primary NGINX configuration file is generally found at /etc/nginx/nginx.conf. This file controls the global configuration settings that apply across the entire NGINX server. Let's assume we have a server named "StarDust" which streams movies. Here’s an example configuration file:

worker_processes  1;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;

    sendfile        on;

    keepalive_timeout  65;

    server {
        listen       80;
        server_name  localhost;

        location / {
            root   html;
            index  index.html index.htm;
        }

        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

In the StarDust server configuration above, the worker_processes directive specifies the number of worker processes that NGINX runs. Each worker can handle many connections thanks to NGINX’s asynchronous architecture. For optimal performances, configuration should be equal to the number of CPU cores available on the server.

The events block encloses directives related to connection processing. worker_connections define the maximum number of simultaneous connections each worker process can handle.

Within the http block, overall configuration directives for HTTP and HTTPS (if SSL is enabled) are defined. It includes server blocks, which correspond to virtual servers. Each virtual server can listen on different ports, and different configuration can be applied to different servers.

The server block includes settings that apply to the specific server. Here, our "StarDust" server is listening on port 80, and the server_name directive is set to localhost. This means that this server block is applied if the Host header of the HTTP request matches "localhost".

The location block indicates a particular route on the server. For instance, location / applies to the entire server because / is the root of any URL path. The server will display index.html or index.htm from the nginx/html directory when a client sends a request to the server.

The error_page directive is used to configure the error pages that visitors see when an error occurs. Here an error 500, 502, 503, or 504 will show the 50x.html page.

Let's add another movie streaming server, "Moonlight", to the "StarDust" server. We can simply add another server block in the http block:

http {
    # other configurations

    server {
        listen       80;
        server_name  localhost;

        # other configurations
    }

    server {
        listen       81;
        server_name  moonlight.local;

        location / {
            root   /srv/moonlight;
            index  index.html;
        }

    }
}

In this new NGINX configuration, "Moonlight" server is listening on port 81 and would be applied if the Host header of the HTTP request matches "moonlight.local". As with "StarDust" server, it has a location block to specifically route / from root /srv/moonlight.

While these examples have been simplistic, NGINX configuration can be extended and customized to a large extent. For instance, NGINX can be set up as a load balancer, a reverse proxy server, a mail proxy server and so on.

The best way to master NGINX configuration is by practice and experience. Strive to understand the basic directives and how they interact within the context of larger blocks. Gradually, you'll find the logic behind the structure will unfold, and you'll be capable of harnessing the full power of NGINX.