Network Block Device
C Shell M4 Makefile
Latest commit 3267922 Feb 17, 2017 Eric Blake committed with yoe doc: Fix some minor issues
Fix a grammar nit, and resolve a conflict between two extensions
picking the same command number (BLOCK_STATUS is the older proposal,
so it keeps command 7, RESIZE gets command 8).

Signed-off-by: Eric Blake <>
[added in missing typo fix]
Signed-off-by: Wouter Verhelst <>
Failed to load latest commit information.
.travis Do travis builds on OSX, too. Nov 18, 2015
doc doc: Fix some minor issues Feb 21, 2017
gznbd gznbd: use atoll() to convert size argument Oct 2, 2014
man Re-sort options in this man page Dec 20, 2016
support Improve version-generating thing Oct 10, 2015
systemd Don't forget to ship the nbd@.service.tmpl file Jul 13, 2016
tests Don't use relative paths for certdir Dec 19, 2016
.dir-locals.el maint: Let emacs know our preferred style Oct 20, 2016
.gitignore build: Ignore copied file during in-tree build Oct 20, 2016
.travis.yml Re-enable OSX for travis Apr 4, 2016
COPYING Add the actual text of the GPLv2, as the license requires us to Dec 2, 2013
CodingStyle r176: Add CodingStyle document Aug 5, 2006 Use AM_CONDITIONAL rather than AC_SUBST Jan 23, 2017 Add CII Best Practices badge. No, we're not ready yet. Aug 11, 2016 Add systemd directory to autogen, too Jun 23, 2016
backend.h Test the exptrim() function Nov 7, 2015
buffer.c build: Fix build with older gcc Feb 21, 2017
buffer.h Add GnuTLS infrastructure Nov 3, 2016
cliserv.c Add the set_nonblocking function Nov 3, 2016
cliserv.h Add the set_nonblocking function Nov 3, 2016 Use AM_CONDITIONAL rather than AC_SUBST Jan 23, 2017
coverity_model.c Create Coverity model Jan 21, 2014
crypto-gnutls.c build: Fix build with older gcc Feb 21, 2017
crypto-gnutls.h Add GnuTLS infrastructure Nov 3, 2016
lfs.h Improve indentation to avoid this kind of thing from happening again. Dec 6, 2011
make-integrityhuge.c Add integrity test for huge writes. Fix speed calc problem. May 28, 2011
maketr Add transaction log support and integrity test May 21, 2011
nbd-client.c Reorder tls initialization Nov 20, 2016
nbd-debug.h Make include of "config.h" not use system include path Apr 11, 2016
nbd-server.c Don't seek() in files without holding a lock. Jan 23, 2017
nbd-trdump.c Don't send to syslog from nbd-trdump May 29, 2011
nbd.h Add the NBD_FLAG_CAN_MULTI_CONN flag, unless copyonwrite was selected Dec 19, 2016
nbdsrv.c Don't seek() in files without holding a lock. Jan 23, 2017
nbdsrv.h Don't seek() in files without holding a lock. Jan 23, 2017
netdb-compat.h Fix typo in include guard test Dec 27, 2012
treefiles.c Don't seek() in files without holding a lock. Jan 23, 2017
treefiles.h Fix race condition Jan 1, 2016


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Welcome to the NBD userland support files!

This package contains nbd-server and nbd-client.

To install the package, do the normal configure/make/make install dance. You'll need to install it on both the client and the server.

Note that released nbd tarballs are found on sourceforge.


If you want to send a patch, please do not open a pull request; instead, send it to the mailinglist

Using NBD

NBD is quite easy to use. First, on the client, you need to load the module and, if you're not using udev, to create the device nodes:

# modprobe nbd
# cd /dev
# ./MAKEDEV nbd0

(if you need more than one NBD device, repeat the above command for nbd1, nbd2, ...)

Next, write a configuration file for the server. An example looks like this:

# This is a comment
    # The [generic] section is required, even if nothing is specified
    # there.
    # When either of these options are specified, nbd-server drops
    # privileges to the given user and group after opening ports, but
    # _before_ opening files.
    user = nbd
    group = nbd
    exportname = /export/nbd/export1-file
    authfile = /export/nbd/export1-authfile
    timeout = 30
    filesize = 10000000
    readonly = false
    multifile = false
    copyonwrite = false
    prerun = dd if=/dev/zero of=%s bs=1k count=500
    postrun = rm -f %s
    exportname = /export/nbd/experiment
    # The other options are all optional

The configuration file is parsed with GLib's GKeyFile, which parses key files as they are specified in the Desktop Entry Specification, as can be found at While this format was not intended to be used for configuration files, the glib API is flexible enough for it to be used as such.

Now start the server:

nbd-server -C /path/to/configfile

Note that the filename must be an absolute path; i.e., something like /path/to/file, not ../file. See the nbd-server manpage for details on any available options.

Finally, you'll be able to start the client:

nbd-client <hostname> -N <export name> <nbd device>


nbd-client -N otherexport /dev/nbd0

will use the second export in the above example (the one that exports /export/nbd/experiment)

nbd-client must be ran as root; the same is not true for nbd-server (but do make sure that /var/run is writeable by the server that nbd-server runs as; otherwise, you won't get a PID file, though the server will keep running).

There are packages (or similar) available for the following operating systems:

  • Debian (and derivatives, like Ubuntu): nbd-client and nbd-server, since Debian woody.
  • Gentoo: the nbd ebuild in the sys-block category, available in Portage since 2002.
  • FreeBSD: net/nbd-server, available in the ports tree since 2003. FreeBSD doesn't have kernel support for NBD, so obviously the client isn't built there.
  • SuSE: nbd, in SuSE 10.0
  • Fedora: nbd, since Fedora 7
  • uClibc's buildroot script also seems to have support for NBD.

If you're packaging NBD for a different operating system that isn't in the above list, I'd like to know about it.

For questions, please use the mailinglist.