The HOWTO recommends this command in the simple tdbsam PDC setup's version of smb.conf: add user to group script = /usr/sbin/usermod -G %g %u According to "man usermod" -G must be followed by a comma-separated list of ALL groups other than the user's default group. Any groups memberships not explicitly listed will be lost. This is not the correct way to "add" a group. Also there is no "remove user from group script" option given.
Handing off to jht since it's docs related.
Fixed. - John T.