There are certain directories on some systems (e.g., the /proc tree under Linux) that are either not of interest to clients or are infinitely deep (recursive). This parameter allows you to specify a comma-delimited list of directories that the server should always show as empty. Note that Samba can be very fussy about the exact format of the "dont descend" entries. For example you may need ./proc instead of just /proc. Experimentation is the best policy :-) /proc,/dev