groupThis specifies a UNIX group name that will be
assigned as the default primary group for all users connecting
to this service. This is useful for sharing files by ensuring
that all access to files on service will use the named group for
their permissions checking. Thus, by assigning permissions for this
group to the files and directories within this service the Samba
administrator can restrict or allow sharing of these files.In Samba 2.0.5 and above this parameter has extended
functionality in the following way. If the group name listed here
has a '+' character prepended to it then the current user accessing
the share only has the primary group default assigned to this group
if they are already assigned as a member of that group. This allows
an administrator to decide that only users who are already in a
particular group will create files with group ownership set to that
group. This gives a finer granularity of ownership assignment. For
example, the setting force group = +sys means
that only users who are already in group sys will have their default
primary group assigned to sys when accessing this Samba share. All
other users will retain their ordinary primary group.If the force user
parameter is also set the group specified in
force group will override the primary group
set in force user.force useragroup