This is a quick – “so that’s how I did it”
Connecting to an rsync share on the NasDuo;
rsync -v <filename> <user>@192.168.x.x::<share>
Where the user is listed under the ‘Advanced Options’ of the share. I used a user without a password, nogroup and all the rights disabled.
For me it was the double colon. Before that I got an error
ssh: connect to host 192.168.7.11 port 22: Connection refused
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(235) [sender=3.1.2]