NBD server with stable plugin ABI and permissive license
nbdkit is an NBD server. NBD — Network Block Device — is a protocol for accessing Block Devices (hard disks and disk-like things) over a Network.
The key features of nbdkit 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/C++, Go, Lua, Perl, Python, OCaml, Ruby, Rust, shell script or Tcl.
- Filters can be stacked in front of plugins to transform the output.
For documentation, see the docs directory.
There are many NBD clients, but the nbdkit project has a companion client library called https://gitlab.com/nbdkit/libnbd
This software is copyright (C) Red Hat Inc. and licensed under a BSD license. See LICENSE for details.
Building from source
- Linux, macOS, Windows, FreeBSD, OpenBSD or Haiku
- GCC or Clang
- GNU make
Recommended for TLS (authentication and encryption) support, but it is possible to build without it:
- gnutls >= 3.3.0
For Windows support see the Windows section below.
For macOS support see the macOS section below.
To build the man pages, you will optionally need to install:
- Pod::Man and Pod::Simple (Perl libraries)
For SELinux socket labelling support:
For the gzip filter:
For the xz filter:
For the memory plugin with allocator=zstd:
For the curl (HTTP/FTP) plugin:
For the ssh plugin:
- libssh >= 0.8.0 (this is a different library from libssh2 - that will not work)
For the iso plugin:
- xorriso or genisoimage or mkisofs
For the floppy plugin:
- iconv (on Linux this is built into glibc, on other systems it may be a separate library)
For the libvirt plugin:
For the libguestfs plugin, and to run parts of the test suite:
- guestfish (from libguestfs)
For the ext2 filter:
For the linuxdisk plugin:
- mke2fs >= 1.42.10 (from e2fsprogs)
For the nbd plugin, to get URI and TLS support, and also to run parts of the test suite:
- libnbd >= 0.9.8
For the bittorrent plugin:
For the blkio plugin:
For the containerized data importer (CDI) plugin:
For the Perl and example4 plugins:
- perl interpreter
- perl development libraries
- perl modules ExtUtils::Embed
For the Python plugin:
- python interpreter (version 3 only)
- python development libraries
- python unittest to run the test suite
- boto3 is required to run the S3 plugin written in Python
For the OCaml plugin:
- OCaml >= 4.03
For the Tcl plugin:
- Tcl development library and headers
For the Lua plugin:
- Lua development library and headers
For the Rust plugin:
- cargo (other dependencies will be downloaded at build time)
To be able to write plugins in golang:
- go >= 1.13
For bash tab completion:
- bash-completion >= 1.99
To test for memory leaks (
- valgrind program and development headers
For non-essential enhancements to the test suite:
- ip, ss (from iproute package)
- losetup (from util-linux package)
- mke2fs (from e2fsprogs)
- nbdcopy, nbdinfo, nbdsh (from libnbd)
- qemu-img, qemu-io, qemu-nbd (usually shipped with qemu)
- sfdisk (from util-linux)
- stat (from coreutils)
To build from tarball: To build from git: autoreconf -i ./configure ./configure make make make check make check
On FreeBSD and OpenBSD which do not have GNU make by default you must
gmake instead of
To run nbdkit from the source directory, use the top level ./nbdkit wrapper. It will run nbdkit and plugins from the locally compiled directory:
$ ./nbdkit example1 -f -v ./server/nbdkit ./plugins/example1/.libs/nbdkit-example1-plugin.so -f -v [etc]
Optionally run this command as root to install everything:
Since nbdkit >= 1.16, only Python >= 3.6 is supported.
By default nbdkit uses the Python version of the Python interpreter called “python” on the current $PATH. If you have parallel versions of Python installed then you can choose a different version by setting the PYTHON variable when configuring. For example:
Most recent (less than, say, 8 years old) versions of the OCaml compiler should work. By default the configure script should detect the bytecode and native code compilers and enable either one or both.
To enable OCaml warnings and turn them into hard errors (developers only):
./configure OCAMLOPTFLAGS="-warn-error +A-3"
Running the tests
To run the test suite:
If there is a failure, look at the corresponding
for debug information.
A few tests require root privileges, and are skipped by default. To run them you must do:
If you have the proprietary VDDK library, you can test nbdkit-vddk-plugin against the library like this:
make check-vddk vddkdir=vmware-vix-disklib-distrib
Running the benchmarks
To run benchmarks:
Tarballs are available from: http://libguestfs.org/download/nbdkit
If you are packaging nbdkit, use:
providing extra information about the distribution, and/or distro-specific versions. It helps us with troubleshooting bug reports. (Also, talk to us!)
Install the valgrind program and development headers.
./configure --enable-gcc-warnings --enable-valgrind
When testing use:
make check make check-valgrind
For development ideas, see the TODO file.
The upstream git repository is: https://gitlab.com/nbdkit/nbdkit
Please send patches to the libguestfs mailing list: https://www.redhat.com/mailman/listinfo/libguestfs
For further information, see: https://libguestfs.org/ https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md
Address sanitizer (ASAN)
You can compile nbdkit with clang and ASAN with:
./configure CC=clang CXX=clang++ \ CFLAGS="-O0 -g -fsanitize=address -fno-omit-frame-pointer" \ --disable-linker-script \ --disable-golang make clean make ASAN_OPTIONS="allocator_may_return_null=1 detect_leaks=false" make check
./configure CFLAGS="--coverage -g" LDFLAGS="--coverage -g" make clean make make check lcov -c -d . -o gcov.info genhtml -o coverage gcov.info
Open your browser and examine the
coverage/ directory. At the time
of writing (2020-04) test coverage of the server is reasonable, but
things are much worse for certain plugins and filters.
nbdkit works on macOS and is mostly feature complete. Some tests may fail or be skipped.
We have tested macOS 12 (Monterey) using MacPorts. Other versions of macOS and Homebrew may work too.
We installed the following MacPorts packages:
We configured nbdkit using:
./configure --enable-gcc-warnings --disable-perl \ CFLAGS="-g -O2 -I/opt/local/include" \ LDFLAGS="-L/opt/local/lib"
Experimentally, the server can be compiled on Windows or cross-compiled from Linux using mingw-w64. Only a small subset of features are available. To find out what is missing read the TODO "Windows port".
Note that GCC or Clang is required even if you are compiling on Windows because of some C language extensions we use. MSVC will not work.
Cross-compiling from Linux to Windows
For the rest of this section we talk about cross-compiling for Windows using Linux and mingw-w64. At a minimum you will need:
- mingw-w64 GCC
- mingw-w64 dlfcn
- mingw-w64 winpthreads
- mingw-w64 gnutls (optional, but highly recommended)
- wine (if you want to run it on Linux)
You may want to patch Wine with this patch which adds support for AF_UNIX sockets. It is needed to get most of the test suite to work, but if you don't care about the -U option then it is not needed. https://www.winehq.org/pipermail/wine-devel/2021-May/187049.html
Other mingw-w64 libraries may be installed which will add functionality (see full list of requirements above), but you may end up hitting areas we have not compiled or tested before.
To cross compile do:
mingw64-configure --disable-ocaml --disable-perl --disable-vddk mingw64-make
You can test if the server is working by doing:
(This usually runs wine automatically. If not, you may need to prefix the command "wine nbdkit.exe ...")
To see which plugins and filters were compiled:
find plugins filters -name '*.dll'
You can run them under Wine without installing using eg:
./nbdkit.exe -f -v memory 1G
You can run the test suite in the usual way:
Running the cross-compiled binary on Windows
To test the binary on a real Windows system you will need to copy
server/.libs/nbdkit.exe, any plugins and filters you need
filters/*/.libs/*.dll), and many mingw
libtool creates files called nbdkit.exe in the top level directory and in server. These are the stripped binaries. The "real" binaries are located in hidden
The top level
.libs/nbdkit.exeis the wrapper used to run nbdkit from the build directory, not the server binary. You need
To find the list of mingw DLLs I ran nbdkit.exe iteratively until Windows stopped complaining about missing libraries. You could also use a tool like Dependency Walker.
If you copy everything into a single directory on the Windows server then you should be able to run nbdkit normally, eg:
nbdkit.exe -f -v nbdkit-memory-plugin.dll 1G
You will probably need to open port 10809 on the Windows Firewall.