xenial (1) xnbd-client.1.gz

Provided by: xnbd-client_0.3.0-1ubuntu1_amd64 bug

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.