[Samba] Samba dns update failing

[Jens Kuipers]

Hey Samba!

I'm trying to join a Samba file server to the Samba PDC and although it 
works well I have some issues regarding the DNS. Whenever I try to run 
samba_dnsupdate I get the following response.
     samba_dnsupdate --verbose --all-names
     IPs: ['10.0.20.1']
     Traceback (most recent call last):
       File "/usr/sbin/samba_dnsupdate", line 523, in <module>
         sub_vars = get_subst_vars(samdb)
       File "/usr/sbin/samba_dnsupdate", line 261, in get_subst_vars
         vars['DNSDOMAIN'] = samdb.domain_dns_name()
       File "/usr/lib/python2.7/dist-packages/samba/samdb.py", line 650, 
in domain_dns_name
         return domain_dn.canonical_str().split('/')[0]
     AttributeError: 'NoneType' object has no attribute 'canonical_str'

Which in turn references to this part of the samdb.py file:
      def domain_dns_name(self):
             """return the DNS name of the domain root"""
             domain_dn = self.get_default_basedn()
             return domain_dn.canonical_str().split('/')[0]

It seems that there is no value returned but I'm afraid that I myself 
can not find out why. Can someone point me to the right redirection or 
explain what is missing?

The smb.conf file for good measure:
     [global]
       netbios name = ldb-server
       workgroup = LDB-BEHEER
       security = ADS
       realm = ldb-beheer.nl
       encrypt passwords = yes

       idmap config *:backend = tdb
       idmap config *:range = 70001-80000
       idmap config <win domain>:backend = ad
       idmap config <win domain>:schema_mode = rfc2307
       idmap config <win domain>:range = 3000000-4000000

       winbind nss info = rfc2307
       winbind trusted domains only = no
       winbind use default domain = yes
       winbind enum users = yes
       winbind enum groups = yes

       vfs objects = acl_xattr
       map acl inherit = yes
       store dos attributes = yes

Thanks in advance,
Jens Kuipers