a fast fix is to rename the section [/opt/ltsp/stretch] to [opt/ltsp/stretch]
then everything works fine. A request to the developer: "Negotiation failed/8a: Requested export not found" doesnt help on debugging. I have to trace the nbd-server to find my solution. Please give us a parameter for the loglevel and make a more verbose log: "Negotiation failed/8a: Requested export not found: $request" This could help a lot! Thanks!