Make AD domain account member of local group in Linux
 

I'm using RHEL 6 that I've figured out (finally...) how to integrate it in a MS Active Directory domain. I've used Winbind to achieve this. For now, I need to enable Samba shares but it seems that this working only if the permissions on the shares are set using the AD groups.
More clearly I would say that what I want to achieve is to have AD account being a member of a Linux local group.

I've ran the command below :

[root@hqltest2 samba]# usermod -a -G localgroup MYDOMAIN\user

and I can see from /etc/group that my domain user is now member of my local Linux group.

In my smb.conf file, I set permissions for the share to the local group

valid users = +localgroup

However, the user is not able to browse the share. On the other hand, this works perfectly if the permissions are granted to the AD domain group of the user. Apparently, Linux doesn't handle correctly the membership of the AD domain account to the local group.

Does somebody has a clue how to sort it out?