Experimente abaixo o apache virtualhost e substitua "ip_address" por IP real
NameVirtualHost ip_address:80
<VirtualHost ip_address:80>
ServerName www.domain.com
DocumentRoot /var/www/html
ErrorLog logs/error.log
CustomLog logs/access.log combined
</VirtualHost>
<VirtualHost ip_address:80>
ServerName amg.domain.com
DocumentRoot /var/www/amg.domain.com/html
ErrorLog logs/subdomain_error.log
CustomLog logs/subdomain_access.log combined
</VirtualHost>