If you carefully read the unslung notes & disk behaviour section you’ll see that the HDD ports were reversed in the latest version.
Port 1 is named /hdd/ & Port 2 is named /flash/
The names have nothing to do with what’s connected to the ports
So, the correct path to a HDD on port 2 is /share/flash/data/public
0.2.4-2 is very old & the notes have not been updated for unslung 6.8
You’d be better off using a nightlies version & using the how to found at http://wiki.fireflymediaserver.org/NSLU2_Installation