How to create dynamic subdomain and install SSL certificate – 2024 Easy Way

In this guide, we’ll walk through the steps to create dynamic subdomains on a VPS and install SSL certificates using Let’s Encrypt with DNS challenge. Follow the steps below to set up your VPS for dynamic subdomains and secure them with SSL:

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Step 1: Create a Wildcard DNS Record

1. Go to your DNS provider and create a wildcard * A record.
2. Point the wildcard record to your VPS’s IP address. This allows any subdomain (e.g., randomtext.domain.com) to resolve to your VPS.

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Step 2: Verify DNS Changes

1. Confirm that the domain is correctly pointed to your VPS using DNSChecker.org.
2. Ensure the A record for *.yourdomain.com resolves to your VPS’s IP address.

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Step 3: Set Up Nginx for Dynamic Subdomains

server {
    listen 80;
    listen [::]:80;
    listen 443 ssl http2;
    listen [::]:443 ssl http2;

    server_name *.yourdomain.com;

    client_max_body_size 20M;

    root /var/www/wildcard;
    error_log /var/www/wildcard/error.log;
    access_log /var/www/wildcard/access.log;


    try_files $uri $uri/ /index.php?$args;
    index index.php index.html;

    location ~ \.php$ {
        include fastcgi_params;
        fastcgi_pass unix:/run/php/php8.1-fpm.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
   }
}

1. Log in to your VPS and create a basic Nginx above configuration for handling dynamic subdomains.
2. Configure the server block in Nginx to accept any subdomain (server_name *.yourdomain.com;).

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Step 4: Test Nginx Configuration

1. Run the command nginx -t to check for any configuration errors.
2. If no errors are found, restart Nginx by running sudo systemctl restart nginx.

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Step 5: Access Your Dynamic Subdomain

• Now, visit any subdomain, for example, randomtext.yourdomain.com. You should see your website’s content loading under the dynamically generated subdomain.

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Step 6: Install SSL Certificates (Let’s Encrypt with DNS Challenge)

1. Use Certbot to issue SSL certificates for your wildcard domain (*.yourdomain.com) using the DNS challenge method.

• install certbot : sudo apt install certbot python3-certbot-nginx
• Command: sudo certbot certonly --manual --preferred-challenges=dns -d "*.yourdomain.com".

1. Follow the instructions to add the DNS TXT record as required by Let’s Encrypt for domain validation.

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Step 7: Add SSL Configuration in Nginx

1. Update your Nginx configuration to use the SSL certificates.

• Add the SSL certificate paths in the Nginx server block for your dynamic subdomains.

   ssl_certificate /etc/letsencrypt/live/yourdomain.com/fullchain.pem;
   ssl_certificate_key /etc/letsencrypt/live/yourdomain.com/privkey.pem;

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Step 8: Verify and Restart Nginx

1. Run nginx -t again to ensure there are no errors in your SSL configuration.
2. If no issues are found, restart Nginx to apply the changes: sudo systemctl restart nginx.

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Step 9: Success!

• Your dynamic subdomains are now secured with SSL certificates. You can now access any subdomain like randomtext.yourdomain.com over HTTPS.

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By following these steps, you’ve successfully set up dynamic subdomains with SSL certificates on your VPS!