I currently have a domain, call it example.com, hosted on Dreamhost, and also a Linode VPS. The Linode lives in a subdomain of the Dreamhost domain, foo.example.com. What I want is to configure reverse DNS so that it will report itself as being at foo.example.com.
What I don't know is how to accomplish this. I don't understand DNS very well, and while Linode seems to have facilities for managing a DNS slave zone, I'm worried about screwing up the DNS on Dreamhost. I still want the domain registered there for unrelated reasons.