[Samba] Is Samba unable to resolve secodary group membership?

Michael Schwarz schwarz at uni-paderborn.de
Thu Oct 8 07:51:27 UTC 2020

Am 07.10.20 um 17:29 schrieb Rowland penny via samba:
> On 07/10/2020 16:00, Michael Schwarz via samba wrote:
>> Hello,
>> I have a somewhat complicated problem and so far I have not been able 
>> to find any hints that have brought me further towards a solution:
> This is a bit hard to follow, but certain things stand out, your 
> smb.conf file is from a Unix domain member, yet you are trying to use 
> local Unix groups. You also seem to be using very low numbers for the 
> AD users and groups, numbers I wouldn't recommend, you also mention 
> CTDB, but you do not have 'clustering = yes' in your smb.conf.
> You shouldn't be getting 'WBC_ERR_DOMAIN_NOT_FOUND'
> Can you explain your set up a bit better ?
Hi Rowland,

thanks for your reply. I have postet the output from "net conf list" as 
the /etc/samba/smb.conf is rather short:

[root at lus-gw-1 ~]# cat /etc/samba/smb.conf
   clustering = yes
   include = registry
[root at lus-gw-1 ~]# net conf list
         workgroup = AD
         netbios name = lus-gw
         security = ads
         realm = AD.UNI-PADERBORN.DE
         load printers = no
         winbind use default domain = yes
         winbind scan trusted domains = no
         idmap config * : backend = tdb
         idmap config * : range = 100-999
         idmap config ad : range = 1000-99999999
         idmap config ad : backend = ad
         kerberos method = secrets and keytab
         name resolve order = host bcast
         winbind cache time = 5
         winbind expand groups = 3
         log level = 5
         fileid:algorithm = fsname
         vfs objects = fileid acl_xattr

         path = /scratch
         comment = Lustre re-export
         read only = no
         inherit acls = yes
         inherit permissions = yes
         create mask = 700
         directory mask = 700
         kernel oplocks = yes
         valid users = @meta_pc2_acc_cr2018

The setup at our university is not quite trivial. I can understand that. 
I'll try to explain it again in a different way:

The university computer centre runs a central identity service 
consisting of an LDAP server and its own Kerberos REALM 
(UNI-PADERBORN.DE). All Linux computers and web services etc. are 
connected to this service. For the Windows computers there is a separate 
Active Directory domain (AD.UNI-PADERBORN.DE) served by a windows domain 
conroller. The users are created in both LDAP and ADS, but are not fully 
synchronised. The only reliable key to assign a user in LDAP to a user 
in AD is the user name. The AD knows neither the Unix UIDs nor a home 
directory or the like. Otherwise, the LDAP doesn't know for example the 
SID of an AD-User. The AD can therefore not be taken as the sole source 
for user data on Linux systems. That's why we didn't configure winbind 
as a source in /etc/nsswitch.conf. In order for users on Windows 
computers (member of AD.UNI-PADERBORN.DE) to be able to log on to the 
CIFS cluster by single signon, this cifs cluster is a member of the 
domain. I have created a diagram on 
http://homepages.uni-paderborn.de/mschwar2/LDAP-AD-UPB.jpg. The NFS 
daemon and the CIFS daemon run on the same system.

The directory to be exported via CIFS is located on a Lustre file 
system. This is natively mounted by many Linux computers in our 
computing cluster and rights on this FS are correspondingly bound to the 
Linux UIDs and GIDs.

Samba is obviously able to map an AD user correctly by name to a 
corresponding LDAP user/Linux user. Otherwise I would not be able to 
access data that belongs to my user himself. What does not work is to 
access data belonging to another user and a group of which I am a member 
but which is not my primary group.

I hope this helps a little bit, to understand the setup here.


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