So I got the directory "shared". A group named "Workers" And I got 2 users "Bob" and "An". They both have "Workers" as group. How do I make it so that they both can share in Workers. But only users of the group "Workers".
Make sure the directory is part of the Workers group. Make sure it is usable by the group.
chgrp Workers shared
chmod g+rwx shared
You may want to add the t flag (based on John Hascall's comment)
chmod g+rwxt shared