Nginx Overview

• Global settings — directives that affect the entire NGINX process (user, worker processes, PID file, etc.).
• events block — controls connection handling and the event model.
• http block — top-level container for HTTP-related configuration (server blocks, compression, logging, MIME types, timeouts).
• server blocks — virtual hosts that define how NGINX should respond to requests for specific domains or IPs.

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Global settings

user www-data;
worker_processes auto;
pid /run/nginx.pid;

• user — the system user NGINX worker processes run as (e.g., www-data on Debian/Ubuntu or nginx on CentOS/RHEL).
• worker_processes — number of worker processes. Use auto to let NGINX select based on CPU cores.
• pid — path to the master process PID file used for signaling (reloads, stops).

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Events block

events {
    worker_connections 1024;
    # optionally: use epoll; use kqueue on BSD/macOS
    # use epoll;
}

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HTTP block

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    gzip on;

    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" "$http_user_agent"';

    keepalive_timeout 65;
    types_hash_max_size 2048;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # Server blocks (virtual hosts) and additional configs
    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}

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Server blocks (virtual hosts)

server {
    listen 80;
    server_name example.com www.example.com;

    root /var/www/example.com/html;
    index index.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

• listen — IP and/or port to listen on (commonly 80 for HTTP and 443 for HTTPS).
• server_name — domain(s) or hostnames this block responds to (used to match incoming Host headers).
• root — directory from which files are served for this server block.
• index — default index file(s) for directory requests.
• location / — location block for the site root. try_files $uri $uri/ =404; checks the filesystem and returns 404 if no match.

• $uri and $uri/ are built-in variables representing the requested path and the path treated as a directory.
• The =404 fallback instructs NGINX to return an HTTP 404 status if a file or directory isn’t found.

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NGINX modules

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Directory structure and important files

• Place site configs in sites-available/ and enable them by creating a symlink in sites-enabled/ (this pattern mirrors Apache’s a2ensite workflow).
• Use conf.d/ for smaller reusable fragments or service-specific configuration (e.g., load balancing, SSL snippets).
• Verify your website document root (e.g., /var/www/) and permissions when troubleshooting file serving issues.

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Essential NGINX commands

sudo nginx -t

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

1. Edit or add config files (e.g., create a site in /etc/nginx/sites-available).
2. Test configuration:

sudo nginx -t

3. If the test passes, reload NGINX to apply changes without dropping connections:

# Option A: NGINX signal-based reload
sudo nginx -s reload

# Option B: systemd-based reload on systems using systemd
sudo systemctl reload nginx

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Reload vs restart

• reload (recommended) tells NGINX to re-open files and apply config changes without stopping the master process — less disruptive to active connections.
• restart stops and then starts the service; it can briefly interrupt active connections.

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Common diagnostic commands

• Check service status:

sudo systemctl status nginx

• Follow logs in real time:

# Access log (HTTP requests)
sudo tail -f /var/log/nginx/access.log

# Error log (errors and warnings)
sudo tail -f /var/log/nginx/error.log

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Summary

• nginx.conf is organized into Global settings, events, http, and server blocks.
• Use sites-available and sites-enabled to manage virtual hosts; use conf.d/ for reusable fragments.
• Test changes with nginx -t (or nginx -T for full config) before reloading.
• Prefer reload to apply configuration changes without downtime.
• Check /var/log/nginx/ for access and error logs when troubleshooting.

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Links and references

• Official NGINX documentation: https://nginx.org/en/docs/
• NGINX configuration guide: https://nginx.org/en/docs/beginners_guide.html
• Kubernetes Basics (if deploying behind Kubernetes Ingress controllers)