[Samba] Samba4 idmap operations

[Lukasz Zalewski]

Hi all,
I have been playing with samba4 (Samba 4.0.0alpha12-GIT-9ad9fd5) for a 
few days and so far its working great - clients join the domain, with 
roaming profiles and home directories served from it.
AFAICT the xidNumber is incrementally assigned from a pool of values 
between lowerBound and upperBound. My questions are as follows:

When is this mapping actually generated - i have created new users using 
net newuser username but this mapping was not present soon after the 
creation. Does it get generated when file access is needed? One can 
force its generation using wbinfo:
bin/wbinfo --sid-to-uid S-1-5-21-4036476082-4153129556-3089177936-1006
3000012
which does generate the mapping, but this brings me to the next question:
can this mapping be generated during account creation with specific uid, 
i.e.
net newuser username -uid 503
I am aware that wbinfo can do this for you but when i run it the 
following error occurs
bin/wbinfo 
--set-uid-mapping=503,S-1-5-21-4036476082-4153129556-3089177936-1006
failed to call wbcSetUidMapping: WBC_ERR_DOMAIN_NOT_FOUNDCould not 
create or modify uid to sid mapping

Am I missing something obvious?

And finally is there a way to ammend/add those values using ldap 
interface instead of operating directly on ldb database files? If so 
what would be the bind/base dn for such operation?

Many thanks

Lukasz