Provided by: nbd-client_2.9.25-2ubuntu1_amd64 bug


       nbd-client  -  connect  to  a  server  running nbd-server(1), to use its    exported block


       nbd-client host [ port ] nbd-device [ -sdp ] [ -swap ] [ -persist ] [ -nofork ] [  -block-
       size block size ] [ -timeout seconds ] [ -name name ]

       nbd-client -d nbd-device

       nbd-client -c nbd-device


       With  nbd-client, you can connect to a server running nbd-server, thus using raw diskspace
       from that server as a blockdevice on the local client.

       To do this, support from the Linux Kernel is necessary, in the form of the  Network  Block
       Device (NBD). When you have that, either in the kernel, or as a module, you can connect to
       an NBD server and use its exported file through a block special file with major mode 43.

       Optionally, long options can also be specified with two leading dashes.


       The following options are supported:

       -block-size block size

       -b     Use a blocksize of "block size". Default is 1024; allowed values  are  either  512,
              1024, 2048 or 4096

       host   The hostname or IP address of the machine running nbd-server. Since 2.9.15, the NBD
              utilities support IPv6.

       -timeout seconds

       -t     Set the connection timeout to "seconds". For this to work, you need a  kernel  with
              support  for  the  NBD_SET_TIMEOUT  ioctl;  this was introduced into Linus' tree on
              2007-10-11, and will be part of kernel 2.6.24.

       port   The TCP port on which nbd-server is running at the server.

              This option is required, unless the -N option is specified.

              The block special file this nbd-client should connect to.


       -c     Check whether the specified nbd device is connected.

              If the device is connected, nbd-client will exit with an exit state of 0 and  print
              the PID of the nbd-client instance that connected it to stdout.

              If  the  device  is  not  connected  or does not exist (for example because the nbd
              module was not loaded), nbd-client will exit with an exit state of 1 and not  print
              anything on stdout.

              If  an  error occurred, nbd-client will exit with an exit state of 2, and not print
              anything on stdout either.


       -d     Disconnect the specified nbd device from the server


       -p     When this option is specified, nbd-client will immediately try to reconnect an  nbd
              device  if the connection ever drops unexpectedly due to a lost server or something


       -S     Connect to the server using the Socket Direct Protocol (SDP), rather than  IP.  See
              nbd-server(1) for details.


       -s     Specifies  that  this NBD device will be used as swapspace. This option attempts to
              prevent deadlocks by performing mlockall() at an  appropriate  time.  It  does  not
              however guarantee that such deadlocks can be avoided.


       -n     Specifies  that  the  NBD  client  should  not detach and daemonize itself. This is
              mostly useful for debugging.

              Note that nbd-client will still fork once to trigger an update to the device node's
              partition table. It is not possible to disable this.


       -N     Specifies  the  name of the export that we want to use. Required if the port is not
              specified, not allowed in the other case.


       Some examples of nbd-client usage:

       · To connect to a server running on port  2000  at  host  "",  using  the
         client's block special file "/dev/nbd0":

         nbd-client 2000 /dev/nbd0

       · To  connect  to a server running on port 2001 at host "", using the
         client's block special file "/dev/nbd1", for swap purposes:

         nbd-client 2001 /dev/nbd1 -swap

       · To disconnect the above connection again (after making sure the block  special  file  is
         not in use anymore):

         nbd-client -d /dev/nbd1


       nbd-server (1).


       The NBD kernel module and the NBD tools have been written by Pavel Macheck (

       The  kernel  module is now maintained by Paul Clements (, while
       the userland tools are maintained by Wouter Verhelst (

       This manual page was written by  Wouter  Verhelst  (<>)  for  the  Debian
       GNU/Linux  system  (but may be used by others).  Permission is granted to copy, distribute
       and/or modify this document under the terms of the GNU General Public License, version  2,
       as published by the Free Software Foundation.

                                         01 October 2011                            NBD-CLIENT(8)