nbdkit is a toolkit for creating Network Block Device servers.

The key features are:

 * Multithreaded NBD server written in C with good performance.

 * Minimal dependencies for the basic server.

 * Liberal license (BSD) allows nbdkit to be linked to proprietary
   libraries or included in proprietary code.

 * Well-documented, simple plugin API with a stable ABI guarantee.
   Lets you export "unconventional" block devices easily.

 * You can write plugins in C, Go, Lua, Perl, Python, OCaml, Ruby,
   Rust, shell script or Tcl.

 * Filters can be stacked in front of plugins to transform the output.