NBD-CLIENT(8)															     NBD-CLIENT(8)

NAME

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

SYNOPSIS

       nbd-client [ bs=blocksize ] [ timeout=seconds ] host port nbd-device [ -sdp ] [ -swap ] [ -persist ] [ -nofork ]

       nbd-client -d nbd-device

       nbd-client -c nbd-device

DESCRIPTION

       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.

OPTIONS

       The following options are supported:

       bs=blocksize
	      Use a blocksize of "blocksize". Default is 1024; allowed values are either 512, 1024, 2048 or 4096

       host   The hostname of the machine running nbd-server.

       timeout=seconds
	      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.

       nbd-device
	      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

       -persist
	      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.

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

       -swap  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.

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

EXAMPLES

       Some examples of nbd-client usage:

       o To connect to a server running on port 2000 at host "server.domain.com", using the client's block special file "/dev/nb0":

	 nbd-client server.domain.com 2000 /dev/nb0

       o To connect to a server running on port 2001 at host "swapserver.domain.com", using the client's block special file "/dev/nb1",  for  swap
	 purposes:

	 nbd-client swapserver.domain.com 2001 /dev/nb1 -swap

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

	 nbd-client -d /dev/nb1

SEE ALSO

       nbd-server (1).

AUTHOR

       The NBD kernel module and the NBD tools have been written by Pavel Macheck (pavel@ucw.cz).

       The  kernel  module is now maintained by Paul Clements (Paul.Clements@steeleye.com), while the userland tools are maintained by Wouter Ver-
       helst (wouter@debian.org)

       This manual page was written by Wouter Verhelst (<wouter@debian.org>) for the Debian GNU/Linux system (but may be used by others).  Permis-
       sion  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.

								    26 May 2009 						     NBD-CLIENT(8)