If nameserver config option is not set (default value), copy Dom0's /etc/resolv.conf on guest. Provide a role to show how to customize /etc/resolv.conf in guest.
These files are roles which you can use with xen-create-image(1) with the --role= option. If you add new roles to the xen-tools distribution in this directory, please document them in the POD code of bin/xen-create-image under "ROLES".