[Samba] Samba4, multi-domain Forest and Unix ID mapping

Andrew Bartlett abartlet at samba.org
Thu Jun 26 12:00:59 GMT 2008

On Wed, 2008-06-11 at 01:33 -0600, Trever L. Adams wrote:
> Good day,
> I wasn't sure whether this should go to the user list or the
> samba-technical list. I chose here based on the descriptions of the list.
> Forgive me if my understanding of the naming is inaccurate. It is my
> understanding that Samba3 (and I believe 4, as well) has a very powerful
> SID<->UID mapping mechanism which will auto create the UID in a range.
> This is what I mean by Unix ID mapping.
> I have read that this as of yet won't work in a forest, even if the
> organization is only one organization. I am hoping this isn't true.

We can map any arbitary SID to unix ID, in principal.  

> I am beginning to look at Samba4 for future implementations within
> organizations I do work for. However, it appears I will need multiple
> domain in one forest functionality. Is this implemented or at least planned?

Samba4 is currently just a single domain, mostly because we have not
looked at what it would take to extend it. 

> If it is implemented/planned is it possible to do the automatic Unix ID
> mapping per above? If it is all one domain, is it possible to do this if
> all the domain controllers/active directory machines are Samba 4?
> Basically, can each domain have its own UID mapping setup and they will
> work in the forest IF, and ONLY IF, the UID mapping doesn't overlap? The
> exact mechanism my questions may bring into mind may be bad.

You could easily use a modal like idmap_rid to automatically handle the
mappings, assuming certain limits in the ranges of SIDs expected to be

> Here is the situation, explained in the context of an extended family
> network:
> Each family has its own domain (Windows and DNS), policies, etc. Each
> has its own file servers, mail domains (DNS), etc. Each may share file
> and printers with other families. This needs to work in Windows and Linux.
> However, here is the killer, root access to Linux machines is not shared
> across domains. Nor should Windows system/net/domain admin abilities.
> However, guests from other families (within the extended family) need to
> be able to view the shared files as well as login (without
> administrative privileges) on computers in the other domains (think
> visiting family).
> To do this, auto SID<->UID maps are a must. Domains within the forest
> will start at 6 at least and grow from there. (This is example isn't far
> from the kinds of things businesses and families ask me to do.)
> Is all of this possible, planned, or just out there?

We would need more help to understand your requirements, and figure out
the best way to implement them, and what assistance you will be able to
provide to get there.  It is best to discuss this on the samba-technical

Andrew Bartlett

Andrew Bartlett
Authentication Developer, Samba Team           http://samba.org
Samba Developer, Red Hat Inc.
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