Provided by: xnbd-client_0.1.0-pre-hg17-c29967ffe2f3-1_amd64 bug


       xnbd-client — connect to a server running xnbd-server(8), to use its exported block device


       xnbd-client  [--blocksize  SIZE]   [--connect]   [--exportname  NAME]  [--recovery-command
       COMMAND]  [--recovery-command-reboot COMMAND]  [--retry COUNT]  [--timeout  SECONDS]  NBD-
       DEVICE  [      HOST        PORT         ...]

       xnbd-client [bs=SIZE]  [timeout=SECONDS] HOST       PORT NBD-DEVICE

       xnbd-client --disconnect NBD-DEVICE

       xnbd-client --check NBD-DEVICE


       With  xnbd-client,  you  can connect to a server running xnbd-server or xnbd-wrapper, 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.

       Long options can also be  specified  with  two  leading  dashes.  Some  options  are  call
       compatible  to  nbd-client(1)  as  are most behavioural switches. This makes xnbd-client a
       plug-in replacement for nbd-client.


       The following options are supported:

       --block-size SIZE
                 Use the provided value as block size.   Default  is  1024;  allowed  values  are
                 either 512, 1024, 2048 or 4096.  For best results use a block size value of 4096

                 For compatibility to nbd-client(1) you can also use bs=SIZE

                 Check whether the specified nbd device is connected.

                 If  the  device  is connected, xnbd-client will exit with an exit state of 0 and
                 print the PID of the xnbd-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), xnbd-client will exit with an exit state of 1 and not
                 print anything on stdout.

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

                 Connect to the nbd-server

                 Disconnect  the  specified nbd device from the server. Terminates execution with
                 an exit state of 0 on success.

       --exportname NAME
                 If the server supports to access devices by an identifier, use NAME  to  request
                 access  to  a  particular  volume.  This command is useful in combination with a
                 xnbd-wrapper      and only  succeeds,  if  the  remote  host  is  exporting  the
                 requested device.

       --retry COUNT
                 Try  up  to "COUNT" times to connect to the associated nbd-server. Default is 1,
                 that is nbd-client will stop after the first unsuccessful try.

                 invoke a specified command "COMMAND" on unexpected disconnection

                 Invoke the reboot(8) command on unexpected disconnection

       --timeout SECONDS
                 Use a timeout period (default is 0 which means not to use a timeout).  Please do
                 not  use this option for now, as it seems not to work due to a bug in the kernel

                 For compatibility to nbd-client(1) you can also use timeout=SECONDS


       The following positional options are supported:

       HOST      The site to connect to a remote xnbd-server.  You  can  specify  any  resolvable
                 hostname, IPv4 or IPv6 address.

       PORT      The port number to connect to on remote side

                 The local nbd-device to be associated with the remote xnbd-server.

       You  can specify multiple host port     tuples. xnbd-client will try to connect to each of
       them in order until it succeeds to establish a connection to a server.


       The NBD device is known to deadlock when not  being  used  altogether  with  the  deadline
       scheduler. Make sure to do:

       echo deadline > /sys/block/nbd0/queue/scheduler


       xnbd-server (8), xnbd-wrapper (8).


       The  NBD kernel module and the NBD tools have been written by Pavel Macheck (
       and is now maintained by Paul Clements.  (

       The  xNBD  userland  (client  and  server)  have  been  written  by   Takahiro   Hirofuchi

       This  manual  page  was  written by Arno Toell ( for the Debian GNU/Linux
       system (but may be used by others). Large parts are verbatim copies of the  original  nbd-
       server  and  nbd-client  manual  pages  written  by  Wouter  Verhelst (
       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