I am running a Samba 3.6.20 for my primary domain controller (+ main file server) and my back up domain controller. Each domain controller has an LDAP backend- the LDAP servers configured for multimaster replication. I have domain trusts established with a Windows 2003 AD domain ("WINDOMAIN") . I have enabled nested groups in smb.conf. Winbind is enabled to support domain trusts. It isn't need to for users in the local samba domain ("SAMBADOMAIN") since the LDAP backend stores unix uid's and gid's as well as samba user SID's. I had a shared directory on the primary server that I wanted to make for easily accessible to members from the trusted Win 2003 domain. Domain trusts worked, and the trusted users had access to the parent directory . But the problem was that every time someone in samba domain created a few new file in the directory, the trusted users did not automatically have access. The new file would inherit the primary group for the file from the parent directory, but none of the ACE's for the trusted domain users. Who ever create the new file could add the trusted domain users to that file's ACL but they usually forgot to. The shared directory is owned by "projectX" group. Originally the directory was a domain group for the samba domain. In the example below, the users thomas , richard and harold are members of the samba domain. e.g. version: 1 dn: cn=projectx,ou=group,o=mydomain.com objectClass: sambaGroupMapping objectClass: posixGroup objectClass: top cn: staff_planning gidNumber: 123 sambaGroupType: 2 sambaSID: S-1-5-21-111111-222222-333333-10123 description: projectx displayName: projectx memberUid: thomas memberUid: richard memberUid: harold entrydn: cn=projectx,ou=group,o=mydomain.com I wanted to be able to add users from the trusted domain to this group. Adding a "WINDOMAIN\user" as a memberUid was not sufficient. So I changed the group to a local "local" (aka "nested" group) - basically by changing the group type from 2 to 4. I could then use the net command to add users from the trusted domain e.g net rpc group addmem projectX "WINDOMAIN\peter " -U "SAMBADOMAIN\Administrator" This would add the sambasidlist attribute to the LDAP entry. e.g. version: 1 dn: cn=projectx,ou=group,o=mydomain.com objectClass: sambaGroupMapping objectClass: posixGroup objectClass: top cn: staff_planning gidNumber: 123 sambaGroupType: 4 sambaSID: S-1-5-21-111111-222222-333333-10123 description: projectX displayName: projectX memberUid: thomas memberUid: richard memberUid: harold entrydn: cn=projectx,ou=group,o=mydomain.com sambasidlist: S-1-5-21-88888-99999-00000-10001 sambasidlist: S-1-5-21-88888-99999-00000-10002 sambasidlist: S-1-5-21-88888-99999-00000-10003 I can also add users and groups from the samba domain to the group with the net command, but there isn't much benefit to this. I can verify the members with "net rpc group members projectX." This worked fine for maybe 6 months. Last week (maybe 2 weeks ago) users from the trusted domain reported that this no longer worked. (If they explicitly have permissions to the file, then they have access but the group membership functionality no longer works.) The "net rpc user info" command only works for local users- but that had always been the ase. E.g. # net rpc user info thomas -U Administrator Enter Administrator's password: Domain Users projectX # net rpc user info "SAMBADOMAIN\thomas" -U Administrator Failed to get groups for 'SAMBADOMAIN\thomas' with error: Could not map names to SIDs. # net rpc user info "WINDOMAIN\peter " -U Administrator Failed to get groups for 'WINDOMAIN\peter' with error: Could not map names to SIDs. A few months ago I updated from Samba 3.5.x to Samba 3.6.20. I do not think this corresponds to the nested groups breaking, since the problem was not reported until months later. The "net rpc group delmem" also no longer works, tho this may be related to the samba upgrade. I can still delete sambasidlist entries with ldap tools. wbinfo shows that the user id's, sids and names are all consistent for trusted users. The getent and id commands work with trusted users. I can make a trusted user the owner of a file. Samba logs show the trusted users being denied access to the files, so it seems clear that the group membership is just not being recognized. Any help is appreciated. Thanks