Export real block device

[Christian Hesse]

I would like to export real block devices. (Created a volume and replaced data file with symbolic link to device file.) Looks like this fails for whatever reason. Possibly it can not determine the device size?

[Michał Belczyk]

Good, this is supposed to fail and it was implemented like this on purpose. You should not touch the directory structure under data_directory or ctrl_directory manually. For the purpose of serving a single block device you can use the stock nbd-server! The way bnbd should be used is to launch a single bnbd instance per single underlying block device (preferably a directly attached physical disk or a local HW raid) with the intention of providing number of easily managed virtual volumes on top of it -- the "single underlying block device" (as characterised by its queue length and maximum request size) will become even more important when the disk traffic fairness according to virtual volumes weights code goes in... Please note that bnbd is NOT a general nbd server replacement and will probably never be. Feel free to hack it yourself in your fork if you really insist to use bnbd this way but I will not merge this code back.