nbdkit 1.17.3 pushes this series which allows you to opt in to API version 2 and has several improvements designed to reduce mandatory copies between Python code and the server: https://www.redhat.com/archives/libguestfs/2019-November/msg00209.html (actual version: https://github.com/libguestfs/nbdkit/commit/a9b2637cf4f00fb8a25ffaf31ee83...) This does _not_ include Eric's counterproposal involving passing flags as kwargs instead of bitmasks that he posted: https://www.redhat.com/archives/libguestfs/2019-November/msg00248.html Nevertheless we may make further changes to the API such as incorporating kwargs (or may not). So don't start coding to this new API just now. Remember that until something is released in one of the stable (even numbered) branches of nbdkit it is still under development and liable to change at any time. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW