cpanel - I'd like to add CNAME for domain.com [duplicate]

I want to change an A record of my root domain www.domain.com to CNAME dyndns.org.

But the cpanel gives me the following error:

already has a SOA record.
You may not mix CNAME records with other records for the same name.

Can you please explain what this means? And how do I fix it?

Solution 1:

Just to clarify, www.example.com is not the root of the domain, example.com is.

A CNAME on www.example.com is valid, but a CNAME on example.com is not - cpanel is right to reject the attempt. A CNAME record can only exist on a name when no other record type exists for that name, since it indicates that all lookups (of any type, not just A) for that name should look up against a different name instead. You must always have at a minimum an SOA record and an NS record on your root name (example.com), so a CNAME conflicts with the existence of those records.