Provided by: nbd-client_2.9.25-2ubuntu1_i386 bug


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


       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

       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 similar.


       -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

         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)