Docker build with alpine fails to run apk

If I create a container with a Dockerfile that just says:

FROM alpine

and do a build. If I then run the resultant container with:

% docker run --dns x.x.x.x -it XXXXX sh

Once inside the container I can do an ‘apk update’ just fine. So it’s clearly that ‘docker build’ is not using the correct name server. So I’m back to the question of: How do I define the IPv4 DNS name server address for docker build?

Thanks,

Rob