Step 1: Create a new directory for your subdomain

mkdir -p /var/www/subdomain.domain.com/public_html

Step 2: Set the correct permissions for the new directory

chown -R www-data:www-data /var/www/subdomain.domain.com/public_html

Step 3: Create a new virtual host configuration file

nano /etc/apache2/sites-available/subdomain.domain.com.conf

Step 4: Edit the virtual host configuration file

<VirtualHost *:80>

    ServerName subdomain.domain.com

    ServerAlias www.subdomain.domain.com

    ServerAdmin admin@domain.com

    DocumentRoot /var/www/subdomain.domain.com/public_html

    ErrorLog ${APACHE_LOG_DIR}/error.log

    CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

Step 5: Enable the new virtual host

a2ensite subdomain.domain.com.conf

Step 6: Restart the Apache2 serve

service apache2 restart