Sometimes the names of the users on the client machines are not identical to the names on the server machine. Samba allows you to specify a mapping of windows user names to UNIX user names. To enable mapping set the username map global option to a filename with the mapping. Some distributions have a default filename already assigned. The map file looks like this:
# Unix_name = SMB_name1 SMB_name2 ...
root = administrator admin
nobody = guest pcguest smbguest
alon = a alon
mom = m mom