regression in NBD 3.27.1

[jozzsi]

As reported in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1133143 and in dracut-ng/dracut#2381 .

Sorry for the lack of details, on this, but likely this is caused by recent changes so I just wanted to bubble up the information in front of the right set of people.

#179 might be related.

[eworm-de]

The issue here is 8273f1e. With this change the prefix /dev/ must not be available. Instead we should make it optional I guess...