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libnbd-release-notes-1.20 - Man Page

release notes for libnbd 1.20


These are the release notes for libnbd stable release 1.20. This describes the major changes since 1.18.

libnbd 1.20.0 was released on 5 April 2024.


Fuzzing found and Eric Blake fixed an assertion which could be triggered by connecting to a malicious server.  This was assigned CVE-2023-5871 (low severity).  See the announcement here: https://lists.libguestfs.org/archives/list/guestfs@lists.libguestfs.org/thread/5CRC7LRTN35WPZZ4BT6NAMH4JGMF47IK/

If you find a security issue, please read SECURITY in the source (online here: https://gitlab.com/nbdkit/libnbd/blob/master/SECURITY).  To find out about previous security issues in libnbd, see libnbd-security(3).

Enhancements to existing APIs

nbd_connect_uri(3) now correctly supports case insensitive URIs.


Improve interop with nbd-server(1) which supports structured replies but not meta context (Eric Blake).


nbdinfo(1) adds support for --isnt, --cannot, --hasnt, which lets you check if features of an NBD server are not supported.

nbdinfo(1) adds support for --uri which just prints the canonical URI of the server.

nbdinfo(1) now prints human sizes for block size constraints (Eric Blake).

Language bindings

New libnbd-rust(3) manual page added, providing an overview for writing Rust programs using libnbd.

Rust documentation has been improved by using a custom translator from our own documentation format (Perl POD) to rustdoc.

Some Rust compiler warnings were fixed (Eric Blake).

OCaml bindings now support zero-copy in AIO pread and pwrite functions.  This change is backwards compatible with existing code. (Thanks Nicolas Ojeda Bar, Anil Madhavapeddy, Simon Cruanes).

OCaml bindings now use Gc.finalize (OCaml-level finalizers instead of C-level finalizers) which improves compatibility in OCaml 5.1.1 and above (Guillaume Munch-Maccagnoni).

OCaml ≥ 4.05 is formally required and checked in ./configure. Previously we did not specify a minimum version of OCaml, but in practice versions older than 4.05 probably didn't work.


Fuzzing approach was changed to use asynchronous commands.  This improves speed of fuzzing greatly and should find more issues.

Multiple CI fixes (Eric Blake).

Respect the user's choice of qemu-nbd, nbdkit and other binaries from (eg) ./configure NBDKIT=/some/nbdkit.  Previously we would often test against binaries found on the path even if the user had specified other binaries to use.

Other improvements and bug fixes

nbdinfo(1) now gracefully disconnects from the server in error cases, improving output (Eric Blake).

struct nbd_handle now contains a magic value which is checked on entry to libnbd, which should identify mistakes where programs calling libnbd pass in an incorrect pointer.


An example was added of how to use userfaultfd to mmap an NBD-backed drive.  See examples/userfault-map.c in the libnbd sources.

Documentation of acceptable handle states in the man pages has been improved.


contrib/libnbd.m4 is a contributed configure test for libnbd (Bruno Haible).

./configure --with-bash-completions will now fail if the required bash-completions package is not installed.

See Also



Eric Blake

Richard W.M. Jones

Thomas Weißschuh


This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Referenced By


2024-04-04 libnbd-1.20.0