[Samba] Samba AD: gidNumber?

[Rowland Penny]

On 26/10/15 22:35, Viktor Trojanovic wrote:
>
>
> On 26.10.2015 23:03, Rowland Penny wrote:
>> On 26/10/15 21:38, Viktor Trojanovic wrote:
>>> I joined a Samba AD member server (file server) to a Samba AD DC. 
>>> This seems to have worked. However, if I try to access the file 
>>> server from the domain administrator account on a Windows client, I 
>>> am asked to provide authorization details. Since I have no other 
>>> privileged users, I am using the domain admin credentials but 
>>> they're not accepted.
>>>
>>> I'm not sure exactly where to look but I think the problem could be 
>>> connected to the following: On my member server, the getent command 
>>> does not yield any results. As per the recommendations on the "Samba 
>>> Member Server Troubleshooting" page, I checked on the DC if the 
>>> group Domain Users has a gidNumber. Well, it doesn't. Neither do my 
>>> users have uidNumbers though this, allegedly, is not such an issue.
>>
>> Yes it is, there is no point in adding a gidNumber to  Domain Users 
>> if you are not going to give your Users a uidNumber.
>>
>> As far as how to add uidNumbers and gidNumbers, well firstly, do you 
>> need to? if your users are never going to actually log into the 
>> member server and this is your only Unix machine, you could use the 
>> winbind 'rid' backend, this will create the ID numbers on the fly.
>> If you have more than one member server, or Unix clients or want your 
>> users to log into the member server, you will probably be better off 
>> using the winbind 'ad' backend. To do this you will need to give your 
>> users a unique uidNumber and Domain Users (at least) a gidNumber. You 
>> can do this by using the ADUC UNIX Attributes tab, by writing your 
>> own script using an ldif, or by using something like the LDAP Account 
>> Manager (LAM).
>>
>> Rowland
> Thanks again for helping, Rowland.
>
> As I mentioned before, both the DC and the member server are Unix 
> running Samba 4.3. The purpose of the member server is to act as file 
> server, nothing more.
>
> The clients are all windows machines and users, they will never log in 
> to one of the unix systems directly. If they are able to access shares 
> on the file server without having to log in, then I guess this 'rid' 
> backend seems to be what I need. Correct? Can you give me some 
> pointers on how to do that, or direct me to the documentation?
>
> Though one has to wonder: There is a wiki how to implement a Samba AD, 
> and how to add a Samba Member Server. I followed the instructions step 
> by step, for both, and now it turns out that the instructions for the 
> member server are not made to fit the configuration of the DC? That's 
> a bit discouraging.
>
> Viktor

The main problem is that idmap.ldb on the DC will allocate an xidNumber 
to a user in the '3000000' range, this xidNumber is used for the users 
uidNumber. If you use the DC as a fileserver and a user stores something 
on the DC and you were to examine the permissions, you will find that it 
doesn't belong to a user but a number. This gets worse, if you have two 
DCs, you can and probably will get different numbers on each DC. Now 
this is not a problem until you do something like copy the file from one 
DC to the other, the file could then belong to another user, this can 
also happen with a member server.

If you use a member server and do not want your users to log into it, 
you can use the winbind 'rid' backend, this will allocate UID numbers to 
your users using an algorithm based on the users RID, this also has the 
affect of creating the same UID on every member server.

If you need to use the DC as a fileserver, then I would advise the use 
of the winbind 'ad' backend. Using this, your users will get the same 
UID everywhere, as the users UID is stored in AD using the uidNumber 
attribute.

To add uidNumber & gidNumber attributes to AD is fairly simple, you can 
do it using ADUC, or by writing your own script around an ldif.

To use the winbind 'rid' backend, see here: 
https://wiki.samba.org/index.php/Idmap_config_rid

Rowland