Research and development on the NBD device driver have been partially funded by REALM Information Technology Inc., 5555 Oakbrook Parkway NW, Norcross, GA. This company recently changed their name to ApplianceWare, Ltd. (http://www.applianceware.com/) and moved to Fremont, CA. We are particularly grateful to them. The driver and its code are released under the GPL and can be found at ftp://oboe.it.uc3m.es/pub/Programs/.