[Samba] How to keep idmapping, when Samba servers becomes part of a Windows AD from a larger organisation.

Denis Cardon denis.cardon at tranquil-it-systems.fr
Tue Nov 26 11:55:55 MST 2013

Hi Laurent,
> Since 2006, I used in my departement a Samba  solutions based on  NT4 style PDC, 2 BDCs and some files servers, desserving one hunderd persons. The backends for passwords and idd are a master and two slave openldap. Now i have to integrate a much larger organisation, an  University Hospital,   running with Windows AD. For political reasons, I should not maintain DCs anymore, but I will still maintain  Windows stations, Linux stations and Linux servers.  One point then is to see if  there is a way to keep the idmapping of users and groups I already have, in order to reduced interventions on file servers and stations to a minimum while migrating. For now, I dont know how to do it.  (Note : new users and groups may  have any Linux « id » we want)
> One point here  is that  I succeeded to test the integration of  a samba member into the AD with  samba 4.x,  winbind and idmap config DOMAIN : backend = rid.  Now I want to go further and look for  a solution for this problem of keeping  idmaps of current users.   Is it possible to have a coherent configuration together for  /etc/ldap.conf, /etc/nsswitch.conf  and /etc/samba/smb.conf for this solution?

With rfc2307/SFU you should be able to do what you plan, provided that 
openldap uid/gid number are not yet used in the target ActiveDirectory.

Using python-ldap and python-win32com, it should be quite easy to read 
the data in the old ldap and recreate the uidnumber and gidnumber 
attribute in the ActiveDirectory after creating the user. Actually I 
have already done the revert, ie populate uid/gid from RID in a Samba4 
directory after a migration from MSAD.

Once you have your uidnumber/gidnumber attributes set, then you just 
have to enable rfc2307 in your winbind or sssd and it should be fine, 
user uid and gid should map to the old value with nsswitch.

However I guess in this case that you'll have to recreate a new password 
for all the users and rejoin all the computer to the domain...

If you want to ease the transition, I think you could go the following 
path: upgrade the samba3 PDC domain to samba4, join a MSAD to the 
samba4, demote the samba4 and make an interdomain trust between the two 
MSAD domains, then you'll buy some time to rejoin the computer to the 
new domain and migrate user accounts.

Hope this helps.


PS : it seems like you are fluent in French. I have a few tutorials in 
Frog tongue at the following address to help in doing a migration : 

> Thanks to help
> and warm thanks for Samba
> Laurent
> --
> Laurent Hubert, PhD
> Professionnel de recherche
> Administration de systèmes Linux, déploiement de solutions Open Source
> Centre d'imagerie moléculaire de Sherbrooke
> Centre hospitalier universitaire de Sherbrooke
> 819 346 1110 x 11836
> pagette: 6475
> http://www.cims.med.usherbrooke.ca

Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0)

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