[Samba] How can I switch from internal dns server to bind9

[felix at epepm.cupet.cu]

I provisioned using the defaults. So now I'm using the internal DNS
server. Since I've been having some issues with it (see Internal dns
server stops forwarding) I would like to change to bind9, but now I don't
have the files samba4 creates to use with it because I started using the
internal dns server.

How can I switch from internal dns server to bind9???

Cheers,
Felix.