Mapping Client Users to Samba / CIFS Users
If the users/passwords on the client PCs differ from those on the Samba server then you'll need to specify the username map option in your/etc/samba/smb.conf file and to create the file that you pointed it to. This should be just be a text file containing single line entries in the format:
!<server user> = <client user>
!fredb = Fred
!jsmith = John
This specifies that the client user "Fred" will map to the server user "fredb" and client user "John" will map to "jsmith" on the server. Note that the mapping rules do not have to be 1:1 - there are various mapping options available - see the references at the foot of the page to learn about more advanced mapping options.