Authoritive primary Name Server

[Raphael]

Hello,

I have two domains  (named  x1.com and x2.com )

How have I to configure a primary name Server to make my Server authoritive
for the two domains (x1.com and x2.com)
This Server will run with Linux (SuSE Distribution 6.4).

The Server should resolve all requests for the domain x1.com and x2.com
Which files have to be modified and which DNS files must be created ?

Many thanks!