Samba doesn't umount a share

[v.demartino2 at virgilio.it]

Dear All, always fighting with samba 3.0.7!

I'm trying to umount  an smb share with (/mnt/smb is part of FBSD filesystem):

VicBSD# umount /mnt/smb/Utenti
umount: /mnt/smb/Utenti : not a file system root directory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Samba seems not to be running anymore 

VicBSD# /usr/local/etc/mysql-server.sh stop
mysql-server isn't running
^^^^^^^^^^^^^^^^^

But......

VicBSD# ps ax| grep smb
11188  ??  DL     0:00.19 [smbiod0]

11337  ??  DL     0:00.29 [smbiod1]

11452  ??  Ss     0:00.14 /usr/local/sbin/nmbd -D -s /usr/local/etc/smb.conf

11458  ??  Is     0:00.01 /usr/local/sbin/smbd -D -s /usr/local/etc/smb.conf

11460  ??  I      0:00.00 /usr/local/sbin/smbd -D -s /usr/local/etc/smb.conf

11520  p2  R+     0:00.00 grep smb



What shoud I do to umount the share? 
Why smbumount, declared in 'man samba' doesn't exist?

Ciao
Vittorio