[Samba] Samba 4 two DCs no matching UID/GID

Tim rintimtim at gmx.net
Wed Dec 10 10:30:45 MST 2014

I will try this tomorrow. Possibly this is my fix.

When a domain is provisioned with rfc2307 it would make sense that Unix attributes especially uid/gid would automatically be set.

A member also needs this to be set for unique fs acls right?

Am 10. Dezember 2014 18:07:02 MEZ, schrieb Rowland Penny <rowlandpenny at googlemail.com>:
>On 10/12/14 16:33, Tim wrote:
>> I think I will only need uid and gid due to fs stuff. There are only 
>> Windows clients in that domain.
>> So when the IDs are the same on both DCs, all will be fine I think.
>> In RSAT there are no Unix attributes set. As an example: user1 has
>> 3000021 on DC1 (first provisioned one). DRS seems fine. On DC2 user1 
>> gets uid 3000017.
>> If I set ID in RSAT Unix attributes after choosing domain, the IDs 
>> mentioned above will be overwritten? Standard in Unix attributes is 
>> that ID is not set. E.g. I set ID 2000021 in RSAT this ID will be set
>> for user1 on both DCs because of use rfc2307 = yes?
>> Regards
>> Tim
>> Am 10. Dezember 2014 16:10:58 MEZ, schrieb Rowland Penny 
>> <rowlandpenny at googlemail.com>:
>>     On 10/12/14 14:39, Tim wrote:
>>         I found this. But I didn't find it related to DC idmapping
>>         replication. I have two pieces of hardware. My goal is
>>         an active directory for the windows clients and a file
>>         The AD should have redundancy (this is why I provisioned two
>>         DCs). The file should integrate snapshots like a NetApp
>>         (snapshots are done by rsnapshot). The snapshot functionality
>>         works so far by mounting cifs shares read only of the backup
>>         hardware. But I will try this via NFS due to permissions.
>>         Mounting cifs shares leads to irritating permissions of
>>         ~snapshot folders ("Everyone" has full permissions). So how
>>         would sssd help to replicate the ids regarding idmapping to
>>         the secondary DC? It seems that this is my only problem.
>>         Another option is to have only one DC with NFS regarding
>>         snapshots and a file server who is integrating the snapshots
>>         as mentioned above. But then I have to backup the idmapping
>>         file of the file server or does it get the ids from the AD DC
>>         so that I don't have to backup? The FS stores the ACL by
>>         the IDs. I am using XFS. Thanks in advance Tim Am 10.
>>         2014 13:48:40 MEZ, schrieb Rowland Penny
>>         <rowlandpenny at googlemail.com>: On 10/12/14 12:21,
>>         rintimtim at gmx.net wrote: Thanks for the advice of copying the
>>         idmap.ldb. That works. After adding zum users the uid and gid
>>         begin to differ again. I read that it is not recommended to
>>         run a DC as a fileserver but in my case it's not really an
>>         option. It's a network of twelve clients, so four servers are
>>         incommensurate to this amount of clients. I searched
>>         sssd, because my nsswitch.conf also has it. But how do I have
>>         to configure it all? My actual nsswitch.conf provides the
>>         following: passwd: files sss shadow: files sss group: files
>>         sss services: files sss netgroup: files sss Another
>>         alternative seems to be regarding the idmap.ldb with my
>>         unidirectional rsync replication of the sysvol-folder.
>>         *Gesendet:* Mittwoch, 10. Dezember 2014 um 11:01 Uhr *Von:*
>>         "Rowland Penny" <rowlandpenny at googlemail.com> *An:* Tim
>>         <rintimtim at gmx.net>, samba at lists.samba.org *Betreff:* Re:
>>         [Samba] Samba 4 two DCs no matching UID/GID On 09/12/14
>>         Tim wrote: But will this idmap.ldb change work for upcoming
>>         new users or groups so that uid/gid will not be different?
>>         wiki tells us about built-in groups. Those have the right
>>         Am 9. Dezember 2014 23:03:44 MEZ, schrieb Rowland Penny
>>         <rowlandpenny at googlemail.com>: On 09/12/14 21:07, Tim wrote:
>>         Hello all, I have a fresh install of two CentOS 7 machines.
>>         DC1 I made a domain provision with --use-rfc2307. In DC2 I
>>         made a join as DC - both exactly as the wiki advised. In fact
>>         of its missing I added the idmap use rfc2307 yes parameter to
>>         smb.conf. I will have an extra share on both DCs. Today I
>>         realized, that wbinfo shows different UID/GID for the same
>>         users or groups on the DC's. I created the users/groups via
>>         RSAT. I don't have a Unix attributes tab in RSAT. Is that my
>>         problem for different uid/gid? Thanks in advance Tim Hi, I
>>         think your problem is that idmap.ldb does not replicate to
>>         new DC, this means that users get different UID's on the two
>>         DC's. If you run: ldbedit -e nano -H
>>         /var/lib/samba/private/idmap.ldb on each DC, you will be able
>>         to see the differences. The cure ? copy idmap.ldb from the
>>         first DC to any secondary DC's after the join. It is
>>         documented here:
>>         https://wiki.samba.org/index.php/Join_a_domain_as_a_DC , near
>>         the bottom of the page. Rowland I take it that you didn't
>>         this page on the wiki:
>>         https://wiki.samba.org/index.php/Samba_AD_DC_HOWTO You are
>>         running into one of the problems why it is not recommended to
>>         use the DC as a fileserver, you have two choices here, either
>>         set up a separate member server to use as a fileserver, or
>>         sssd or nlscd to pull the RFC2307 attributes that you will
>>         need to add to the users/groups. Whatever you do, you will
>>         need to copy idmap.ldb to any secondary DC's. Rowland Did you
>>         search on the samba wiki ???? :
>>         Rowland
>>     OK, another
>>     The only way to ensure that your users have consistent uidNumbers
>>     gidNumbers on **any**  Unix machine, is to use the RFC2307
>>     The attributes are all available out of the box with Samba4, you
>>     have to give your users and groups the required attributes.
>>     Once you have given your users & groups these attributes, you
>then have
>>     to use something to pull these attributes. Winbind is available
>>     Samba, but winbind on the DC is different from the winbind that
>is used
>>     on a member server or client. The winbind that is available on
>the DC
>>     will not pull any RFC2307 attributes other than 'uidNumber' &
>>     'gidNumber'. What this means is, if you want to use different
>>     unixHomeDirectories & loginShell's, you need to use sssd or
>>     Rowland
>By default, no users have a uidNumber and no groups have a gidNumber.
>you use the UNIX_Attributes tab in ADUC, the default start number is 
>10000, though you can change this, I wouldn't bother. Just update any 
>users via ADUC, AD will then store the next uidNumber (or gidNumber)
>you. If you then go to the DC and run 'getent passwd <the user you just
>updated on ADUC>', you will find that the users ID number will have 
>changed to whatever you used in ADUC. This same command should give the
>same result on the second DC, though there may be a problem on both
>if the cache hasn't cleared, if so, wait a short while, or run 'net 
>cache flush'.
>If you update users with ADUC, do not add users with samba-tool and try
>to add the users uidNumber at the same time, you could use a number
>is already in use for another user. You can use the same number for a 
>group as a user, they are different objects.
>If you do use ADUC to add the users uidNumber and the user already has 
>any info stored on the DC, you will need to change the ownership of
>info to the user (the info will show as belonging to the users old 

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