linux - How to add a second-level domain name to the code and automatically perform A record resolution?

Question

Today someone told me about a problem with shopnc secondary merchant domain name resolution.
I don’t understand how to implement it.
is to edit the second-level domain name of a merchant in the background. This domain name will automatically point to the server's IP, as will the pinged address.
I don’t have a chance to see the code implementation now. I would like to ask everyone how this is implemented?
Connected to the interface of a certain dns service provider?

Answer 1

Pan analysis, fill in domain name resolution*

Any second-level domain name you enter will point to the same IP