NAME

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

SYNOPSIS

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

       xnbd-client [OPTIONS] --connect NBD-DEVICE HOST PORT [HOST PORT ..]

       xnbd-client --disconnect NBD-DEVICE

       xnbd-client --check NBD-DEVICE

       xnbd-client [OPTIONS] --getsize64 HOST PORT [HOST PORT ..]

DESCRIPTION

       With xnbd-client, you can connect to a server running xnbd-server or xnbd-wrapper, thus
       using raw diskspace from that server as a block device 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.

OPTIONS

       The following options are supported:

       --blocksize 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|-c
           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 exists but is not connected (i.e. is free for use), xnbd-client will
           exit with code 2 and not print anything on stdout.

           If the device does not exist (for example because the nbd module was not loaded) or if
           an error occurred, xnbd-client will exit with a positive return code other than 2 and
           not print anything on stdout, either.

       --connect|-C
           Connect to the nbd-server

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

       --getsize64
           Report remote disk size in bytes, mimicking blockdev(8).

       --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 an 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
           xnbd-client will stop after the first unsuccessful try.

       --recovery-command COMMAND
           Invoke the specified command on unexpected disconnection

       --recovery-command-reboot: 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 module.

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

POSITIONAL ARGUMENTS

       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

       NBD-DEVICE
           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.

BUGS

       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

SEE ALSO

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

AUTHOR

       The NBD kernel module and the NBD tools have been written by Pavel Macheck (pavel@ucw.cz)
       and is now maintained by Paul Clements (Paul.Clements@steeleye.com).

       The xNBD userland programs have been written by Takahiro Hirofuchi
       (t.hirofuchi@aist.go.jp).

       This manual page was written by Arno Toell (arno@debian.org) 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 (wouter@debian.org).
       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.