This is for VPS and Dedicated server.
If you go to CPanel to add a domain name that is the same as the name of your server, you will get an error message, something like this :
Error from park wrapper: Sorry, subdomains of the hostname cannot be parked.
HOW TO SOLVE THIS :
1. Log in to WHM >> TWEAK SETTINGS >> click on DOMAINS tab.
2. Tick on the radio button that says :
Allow users to park subdomains of the server’s hostname main domain.
3. Go back to CPanel and add that domain name.