How can I set up Samba shares to only be accessed by certain users?

I have a RAID10 array mounted on Ubuntu Server 12.04. I have created a few folders within the mount point and want the following functionality.

There will be 4 users, 3 of them are windows users: 'one' 'two' & 'three'. 'four' is a media streamer that only needs to access the MEDIA share. One Two and Three need to have full access to the media share and their own personal shares (for documents) which no other users but them can access.

Currently, User Four works perfectly (Has full access to the MEDIA folder and can't access folders owned by other users). The problem is, when logged in as the other user, I can't access either share; (tried using valid users = and using chmod to add permissions to no avail).

TL;DR: I need to know how to configure Samba properly to restrict access to certain shares for certain users and allow all of them to access one communal folder (all files on a RAID10 mount).

Solution 1:

Each samba user must have a normal linux account as well.

1. Make sure that every user can access the common media folder on the unix side (without samba); alternatively, you can set force user in smb.conf
2. Make sure each user has a samba password set. You can set it with sudo smbpasswd -a your_user
3. Look at /etc/samba/smb.conf: check if the line security = user is set in the [GLOBAL] section
4. Set your shares in /etc/samba/smb.conf, see example

Example shares:

[allaccess]
    path = /media/common
    read only = no
    writeable = yes
    browseable = yes
    valid users = one, two, three, four
    create mask = 0644
    directory mask = 0755
    ; if you set this, all files get written as this user
    force user = one

This will be accessible via \\yourserver\allaccess

A single user share:

[special]
    path = /home/two/onlytwo
    read only = no
    writeable = yes
    browseable = yes
    valid users = one
    create mask = 0640
    directory mask = 0750

Restart the samba server after the changes with:

sudo service smbd restart