Comment 23 for bug 951526

> Question - how and where is nbd-server started during startup ? What could prevent nbd-server from starting ?

nbd-server ships an initscript in /etc/init.d/nbd-server
If `sudo service nbd-server restart` didn't work, it would be a configuration problem, and since LTSP is responsible for the nbd-server configuration, the problem would be related to LTSP.

But it does work, so it's not an LTSP issue; it might be an nbd-server problem or an upstart problem.
So as I mentioned, you should file a separate bug in the nbd-server package and attach your nbd-server configuration files (in /etc/nbd-server/*) and any related logs you can find in /var/log/syslog.