[Samba] "force group" not working with shared directories

[Sam Hart]

I'm trying my darnedest to set up a samba server to share some directories 
for certain user groups. Several of the shares will be housing databases 
(incl. MS Access) which will be accessed by several users, often at the 
same time, and thus need to deal with both file-locking and group 
ownership.

I have read that I need essentially the following in my smb.conf file:
[lab]   
        path = /usr2/lab
        available = yes   
        public = yes
        guest only = no
        writeable = yes  
        browseable = yes
        valid users = foonly, hart
        only user = no
        oplocks = No
        level2oplocks = No
        create mask = 770
        directory mask = 770
        force group = lab

with the important lines being "create mask", "directory mask" and "force 
group".

The problem is that while the "create mask" and "directory mask" lines 
work, the "force group" line does not, and the group "lab" is never forced 
for new files/directories created in that share. I have tried both "= lab" 
and "= +lab" (not really understanding the difference) and neither worked.

I've had some samba experience in the past, but it has always been 
rudimentary (printer sharing, basic/non-readable file sharing) and trying 
to make this work is baffling me.

Any advice would be mucho apreciated. (oh, and before anyone askes, yes, 
I'm SIGHUP'ing my smbd each time I change the config).

-- 
Sam Hart
University/Work addr. <hart at physics.arizona.edu>
Personal addr. <criswell at geekcomix.com>
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