NBD-SERVER(1)															     NBD-SERVER(1)

NAME

       nbd-server - serve a file as a block device to other computers	 running the GNU/Linux(tm) or GNU/Hurd Operating    System

SYNOPSIS

       nbd-server  [ip:]port filename [ size ] [ -r ] [ -m ] [ -c ] [ -l host list filename ] [ -o section name ] [ -C config file ]

DESCRIPTION

       nbd-server  is  the  server  for  the Linux Network Block Device (NBD). With NBD, a client can use a file, exported over the network from a
       server, as a block device. It can then be used for whatever purpose a normal block device (harddisk, CD-ROM, ...) can be used for.

       NBD can be useful for diskless clients that need swapspace, but you can also create a filesystem on it and use it as though it were a local
       filesystem.

       nbd-server  implements some security through a file called "nbd_server.allow" in the current directory (by default; a different file can be
       chosen with the '-l' option).  This file must list the IP-addresses of clients that are allowed to connect.  If	it  does  not  exist,  all
       clients are able to connect.  If the file is empty, no clients can connect.

OPTIONS

       ip     The ip address the server should listen on. If omitted, 0.0.0.0 (aka "any address") is used.

       port   The  port the server should listen to. A valid port is any number between 1 and 65536; if 0 is used, nbd-server will listen on stdin
	      (so that nbd-server can be ran from inetd)

       filename
	      The filename of the file that should be exported. This can be any file, including "real" blockdevices (i.e. a file  from	/dev).	If
	      the filename includes the literal string "%s", then this %s will be substituded with the IP-address of the client trying to connect.

       size   The size of the block device at the client side. This is especially usefull in conjunction with the -m option

	      Can optionally be followed by one of K,k,M or m, in which case the size will be multiplied by 1024 (K or k) or 1048576 (M or m)

       -r     Export  the  file  read-only.  If a client tries to write to a read-only exported file, it will receive an error, but the connection
	      will stay up.

       -m     Work with multiple files. This can be used to export blockdevices that are larger than the  maximum  allowed  filesize  on  a  given
	      filesystem;  i.e. when the filesystem does not allow files larger than 2GB (which is true for Linux 2.2 and below), you can use this
	      option to store the data in multiple files and export a larger filesystem, if needed.

	      To use this option, you must create a number of files with names in the format "name.X", where "name" is given as the filename argu-
	      ment to nbd-server, and "X" is a number starting by 0 and going up for each file.

	      Allowing more flexibility for this option is planned for future versions.

       -c     Copy  on write. When this option is provided, write-operations are not done to the exported file, but to a separate file. This sepa-
	      rate file is removed when the connection is closed, which means that serving this way will make nbd-server slow down (especially	on
	      large  block  devices  with lots of writes), and that after disconnecting and reconnecting the client or the server, all changes are
	      lost.

       -C     Specify configuration file. The default configuration file, if this parameter is not specified, is /etc/nbd-server/config.

	      Note that the configuration file is always parsed and the entries in the file used, even if an extra server is specified on the com-
	      mand  line.  To  disable	the configuration file entirely, either move it away or use the -C option to point nbd-server(1) to a non-
	      existing or empty configuration file.

	      Also note that if an empty, incomplete, or invalid configuration file is specified, nbd-server will produce a warning about  failure
	      to parse the config file. If the command line contains a fully specified configuration, this warning is harmless and may be ignored.

       host list filename
	      This argument should contain a list of IP-addresses for hosts that may connect to the server. Wildcards are not allowed. If the file
	      does not exist, it is ignored (and any host can connect); If the file does exist, but is empty, no host can connect. By default, the
	      name  'nbd_server.allow'	is used, and looked for in the current directory, unless nbd-server is compiled as a daemon, in which case
	      it is looked for in the root-directory.

       section name
	      If the -o argument is given on the command line, then nbd-server will output a configuration file section with this  as  the  header
	      that  is	functionally equivalent to the other options specified on the command line, and exit. This is useful for migrating pre-2.9
	      nbd-server initscript configuration files to the new format.

EXAMPLES

       Some examples of nbd-server usage:

       o To export a file /export/nbd/exp-bl-dev on port 2000:

	 nbd-server 2000 /export/nbd/exp-bl-dev

       o To export a the same file read-only:

	 nbd-server 2000 /export/nbd/exp-bl-dev -r

       o To export the same file read-write, but make sure changes are lost after restarting the client or the server:

	 nbd-server 2000 /export/nbd/exp-bl-dev -c

SEE ALSO

       nbd-client (8), nbd-server (5), http://nbd.sourceforge.net/roadmap.html

AUTHOR

       The NBD kernel module and the NBD tools were originally written by Pavel Machek (pavel@ucw.cz)

       The Linux kernel module is now maintained by Paul Clements (Paul.Clements@steeleye.com), while the userland tools are maintained by  Wouter
       Verhelst (<wouter@debian.org>)

       On  The Hurd there is a regular translator available to perform the client side of the protocol, and the use of nbd-client is not required.
       Please see the relevant documentation for more information.

       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.

								   09 July 2009 						     NBD-SERVER(1)