Nginx Server_name Wildcard or Catch-all

In Nginx, you can configure server_name directives to handle requests for different domains using wildcard or catch-all patterns. This allows you to handle various subdomains or domains with a single server block. Here’s how you can configure wildcard and catch-all server names in Nginx:

1. Wildcard Subdomains

Wildcard subdomains match any subdomain under a given domain. For example, *.example.com will match www.example.com, blog.example.com, shop.example.com, etc.

Example Configuration:

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

    root /var/www/html;
    index index.html index.htm;

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

Explanation:

• server_name *.example.com;: Matches all subdomains of example.com.

2. Catch-All Domain

A catch-all server block matches any domain or subdomain not explicitly defined in other server blocks. This is useful for handling unknown or wildcard domains.

Example Configuration:

server {
    listen 80 default_server;
    server_name _;  # Matches any server name

    root /var/www/html;
    index index.html index.htm;

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

Explanation:

• listen 80 default_server;: Designates this server block as the default for unmatched domains.
• server_name _;: A catch-all pattern that matches any domain not specified in other server_name directives.

3. Specific and Wildcard Combination

You can combine specific domain names with wildcards to handle both known and unknown domains.

Example Configuration:

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

    root /var/www/html;
    index index.html index.htm;

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

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

    root /var/www/html/subdomains;
    index index.html index.htm;

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

server {
    listen 80 default_server;
    server_name _;

    root /var/www/html/default;
    index index.html index.htm;

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

Explanation:

• First Block: Handles requests for www.example.com and example.com.
• Second Block: Handles all subdomains of example.com.
• Third Block: Acts as a catch-all for any other domains.

4. Example: Handling HTTPS

If you’re using SSL, configure both HTTP and HTTPS:

HTTP to HTTPS Redirect and Wildcard Handling:

# HTTP to HTTPS redirect
server {
    listen 80;
    server_name *.example.com example.com;

    return 301 https://$host$request_uri;
}

# HTTPS handling for specific and wildcard domains
server {
    listen 443 ssl;
    server_name *.example.com example.com;

    ssl_certificate /etc/nginx/ssl/example.com.crt;
    ssl_certificate_key /etc/nginx/ssl/example.com.key;

    root /var/www/html;
    index index.html index.htm;

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

# Default server block for unmatched domains
server {
    listen 443 ssl default_server;
    server_name _;

    ssl_certificate /etc/nginx/ssl/default.crt;
    ssl_certificate_key /etc/nginx/ssl/default.key;

    root /var/www/html/default;
    index index.html index.htm;

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

Explanation:

• HTTP Block: Redirects all HTTP requests to HTTPS.
• HTTPS Blocks: Handles both specific and wildcard domains with SSL.
• Default HTTPS Block: Catches all other domains with default SSL certificates.

5. Testing and Validating Configuration

After configuring Nginx, test the configuration and reload Nginx to apply the changes:

Test Configuration:

sudo nginx -t

Reload Nginx:

sudo systemctl reload nginx

Summary

• Wildcard Subdomains: Use .example.com to match all subdomains.
• Catch-All: Use server_name _; with listen 80 default_server; for unmatched domains.
• Combination: Combine specific names with wildcards for flexible handling.
• HTTPS: Configure HTTP to HTTPS redirects and handle SSL for specific and catch-all domains.

By properly configuring server_name with wildcard and catch-all patterns, you can effectively manage multiple domains and subdomains in Nginx.

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