The all of this file "sharing" stuff is really just the user mounting the remotely available share to the local system. If you are logged into a Windows machine as Ray and request access to a portion of the of the remote machine's file to mount to your local machine you: A) have to be authenticated (who are you) and B) authorized (can you do that). The Samba user on Ubuntu is the part that is authenticated and the Ubuntu user is what is authorized. They are both needed. On a windows machine it is the same, but that is all done in the background using the same user. Samba is not a part of Linux. It is a project that was created using Linux as the OS, so it is not as integrated. Your configuration is the integration.
Originally Posted by ray_silva
Have you added the users? After you do add them, what do you get with these commands?
Edit: I don't use UFW on my Samba servers. I don't use any host based firewalls at all. If you are authenticated to a machine in my network then you are known to me and I don't need to protect myself internally on my LAN. I'm not saying you can't or even that you should or shouldn't use UFW. I'm saying I don't so I have no experience in that area.
sudo pdbedit -L
sudo getent passwd|grep 100