nbd-client man page on Manjaro

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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 host [ port ] nbd-device [ -sdp ] [ -swap ] [ -persist  ]  [
       -nofork	] [ -systemd-mark ] [ -block-size block size ] [ -timeout sec‐
       onds ] [ -name name ]

       nbd-client -d nbd-device

       nbd-client -c nbd-device

       nbd-client -l host [ port ]

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 ker‐
       nel, 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.

OPTIONS
       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.

	      For the deprecated oldstyle protocol, passing a port  number  is
	      required.	 In  the oldstyle protocol, exports are defined by the
	      port on which they are running.

	      For the newstyle protocol, the port number  defaults  to	10809,
	      the  IANA-assigned  port	number for the NBD protocol.  The new‐
	      style protocol is selected automatically by nbd-client when  one
	      of the -list or -name options are used.

       nbd-device
	      The block special file this nbd-client should connect to.

       -check

       -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.

       -disconnect

       -d     Disconnect the specified nbd device from the server

       -list

       -l     Ask the server for a list of available exports. If the server is
	      exporting	 over  IPv6  as	 well as over IPv4, this will list all
	      exports twice; otherwise, it should list them all only once.

	      Note that this option only works with nbd-server processes  run‐
	      ning version 3.1 or above, and must be enabled in server config‐
	      uration (with the "allowlist" option) before it can be used.

       -persist

       -p     When this option is specified, nbd-client will  immediately  try
	      to  reconnect  an	 nbd device if the connection ever drops unex‐
	      pectedly due to a lost server or something similar.

       -sdp

       -S     Connect to the server using the Socket  Direct  Protocol	(SDP),
	      rather than IP. See nbd-server(5) for details.

       -swap

       -s     Specifies	 that  this NBD device will be used as swapspace. This
	      option attempts to prevent deadlocks  by	performing  mlockall()
	      and  adjusting  the  oom-killer score at an appropriate time. It
	      does not however guarantee that such deadlocks can be avoided.

       -systemd-mark

       -m     The systemd init system requires that processes which should not
	      be  killed at shutdown time be marked appropriately by replacing
	      the first letter of their argv[0] with an '@' sign.

	      This option will cause nbd-client to do so.

	      Note that this only works if nbd-client is run from  an  initrd;
	      i.e., systemd will ignore such a mark if run from a systemd unit
	      file or from the command line.

       -nofork

       -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 dis‐
	      able this.

       -name

       -N     Specifies	 the name of the export that we want to use.  Required
	      if the port is not specified; changes the default port for  new‐
	      style negotiation from 10809 in the other case.

	      When this option is specified, nbd-client uses the newstyle ver‐
	      sion of the negotiation protocol.	 This  version	is  much  more
	      flexible	than  the oldstyle negotiation, and should be used for
	      new configurations.

EXAMPLES
       Some examples of nbd-client usage:

       · To  connect  to   a   server	running	  on   port   2000   at	  host
	 "server.domain.com",	using	the   client's	 block	 special  file
	 "/dev/nbd0":

	 nbd-client server.domain.com 2000 /dev/nbd0

       · To  connect  to   a   server	running	  on   port   2001   at	  host
	 "swapserver.domain.com",   using  the	client's  block	 special  file
	 "/dev/nbd1", for swap purposes:

	 nbd-client swapserver.domain.com 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

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 Verhelst (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.

				       $			 NBD-CLIENT(8)
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