you need to create some directories if you haven't already

This is what I did.

Create a directory called DF /opt/ltsp/i386/DF
Create a directory called DF /DF
Create subdirectories off /DF

/DF/ws001
/DF/ws002

and so on one for each node.

you need to edit /etc/exports
---------------------------------------------------------

## LTS-begin ##

#
# The lines between the 'LTS-begin' and the 'LTS-end' were added
# on: Tue Aug 5 08:08:30 BST 2003 by the ltsp installation script.
# For more information, visit the ltsp homepage
# at http://www.ltsp.org
#

/opt/ltsp/i386 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)
/var/opt/ltsp/swapfiles 192.168.2.0/255.255.255.0(rw,no_root_squash,async)

/DF/ws001 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)
/DF/ws002 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)
/DF/ws003 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)
/DF/ws004 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)
/DF/ws005 192.168.2.0/255.255.255.0(rw,no_root_squash,sync)

## LTS-end ##

----------------------------------------------------------