So:
ln -s /usr/bin/tdbbackup /usr/lib/mit/sbin
If you are changing from the internal server: /usr/local/samba/etc/smb.conf
# Global parameters
[global]
workgroup = HH3
realm = HH3.SITE
netbios name = HH16
server role = active directory domain controller
# dns forwarder = 192.168.1.1
idmap_ldb:use rfc2307 = Yes
server services = -dns
Obvious really.