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12 <!-- Fill in your name for FIRSTNAME and SURNAME. -->
13 <!ENTITY dhfirstname "<firstname>Wouter</firstname>">
14 <!ENTITY dhsurname "<surname>Verhelst</surname>">
15 <!-- Please adjust the date whenever revising the manpage. -->
16 <!ENTITY dhdate "<date>$Date$</date>">
17 <!-- SECTION should be 1-8, maybe w/ subsection other parameters are
18 allowed: see man(7), man(1). -->
19 <!ENTITY dhsection "<manvolnum>1</manvolnum>">
20 <!ENTITY dhemail "<email>wouter@debian.org</email>">
21 <!ENTITY dhusername "Wouter Verhelst">
22 <!ENTITY dhucpackage "<refentrytitle>NBD-SERVER</refentrytitle>">
23 <!ENTITY dhpackage "nbd-server">
25 <!ENTITY debian "<productname>Debian GNU/Linux</productname>">
26 <!ENTITY gnu "<acronym>GNU</acronym>">
40 <holder>&dhusername;</holder>
50 <refname>&dhpackage;</refname>
52 <refpurpose>serve a file as a block device to other computers
53 running the &gnu;/Linux(tm) or &gnu;/Hurd Operating
58 <command>&dhpackage; </command>
60 <arg choice=plain><replaceable>[ip@]port</replaceable</arg>
61 <arg choice=plain><replaceable>filename</replaceable></arg>
62 <arg><replaceable>size</replaceable></arg>
63 <arg><option>-r</option></arg>
64 <arg><option>-m</option></arg>
65 <arg><option>-c</option></arg>
66 <arg><option>-l <replaceable>host list filename</replaceable></option></arg>
67 <arg><option>-o <replaceable>section name</replaceable></option></arg>
68 <arg><option>-C <replaceable>config file</replaceable></option></arg>
72 <title>DESCRIPTION</title>
74 <para><command>&dhpackage;</command> is the server for the Linux
75 Network Block Device (NBD). With NBD, a client can use a file,
76 exported over the network from a server, as a block device. It can
77 then be used for whatever purpose a normal block device (harddisk,
78 CD-ROM, ...) can be used for.</para>
80 <para>NBD can be useful for diskless clients that need swapspace,
81 but you can also create a filesystem on it and use it as though it
82 were a local filesystem.</para>
84 <para><command>&dhpackage;</command> implements some security
85 through a file called "@sysconfdir@/nbd-server/allow" (by default; a
86 different file can be chosen with the '-l' option or through a
87 config file specification). This file must list the IP-addresses or
88 network masks of clients that are allowed to connect. If it does not
89 exist, all clients are able to connect. If the file is empty, no
90 clients can connect.</para>
92 <para>Note that while the command line allows for specifying an
93 export, the use of this option is deprecated. It is preferred to
94 make use of a configuration file instead, the format of which is
95 defined in nbd-server(5).</para>
98 <title>OPTIONS</title>
104 <para>The ip address the server should listen on. This may
105 be an IPv4 address, an IPv6 address, or a hostname. In the
106 latter case, nbd-server will do a hostname lookup for the
107 name specified, and will listen on the first address that is
108 returned. For compatibility with past versions of
109 nbd-server, if an IPv4 address is specified, the @ sign that
110 serves as separator between the address and port may be
111 replaced by a colon.</para>
112 <para>If this parameter is not specified, nbd-server will
113 listen on all local addresses on both IPv4 and IPv6. To
114 limit to IPv4, specify the address as 0.0.0.0; to limit to
115 IPv6, specify it as ::.</para>
119 <term><option>port</option>
122 <para>The port the server should listen to. A valid port is
123 any number between 1 and 65536; if 0 is used, nbd-server
124 will listen on stdin (so that nbd-server can be ran from
129 <term><option>filename</option></term>
131 <para>The filename of the file that should be exported. This
132 can be any file, including "real" blockdevices (i.e. a file
133 from /dev). If the filename includes the literal string
134 "%s", then this %s will be substituded with the IP-address
135 of the client trying to connect.</para>
139 <term><option>size</option></term>
141 <para>The size of the block device at the client side. This
142 is especially useful in conjunction with the -m
144 <para>Can optionally be followed by one of K,k,M or
145 m, in which case the size will be multiplied by 1024 (K
146 or k) or 1048576 (M or m)</para>
150 <term><option>-r</option></term>
152 <para>Export the file read-only. If a client tries to write
153 to a read-only exported file, it will receive an error, but
154 the connection will stay up.</para>
158 <term><option>-m</option></term>
160 <para>Work with multiple files. This can be used to export
161 blockdevices that are larger than the maximum allowed
162 filesize on a given filesystem; i.e. when the filesystem
163 does not allow files larger than 2GB (which is true for
164 Linux 2.2 and below), you can use this option to store the
165 data in multiple files and export a larger filesystem, if
168 To use this option, you must create a number of files
169 with names in the format "name.X", where "name" is given as
170 the filename argument to nbd-server, and "X" is a number
171 starting by 0 and going up for each file.
174 Allowing more flexibility for this option is planned for
175 future versions.</para>
179 <term><option>-c</option></term>
181 <para>Copy on write. When this option is provided,
182 write-operations are not done to the exported file, but to a
183 separate file. This separate file is removed when the
184 connection is closed, which means that serving this way will
185 make nbd-server slow down (especially on large block devices
186 with lots of writes), and that after disconnecting and
187 reconnecting the client or the server, all changes are
192 <term><option>-C</option></term>
194 <para>Specify configuration file. The default configuration
195 file, if this parameter is not specified, is
196 <filename>@sysconfdir@/nbd-server/config</filename>.</para>
197 <para>Note that the configuration file is always parsed and
198 the entries in the file used, even if an extra server is
199 specified on the command line. To disable the configuration
200 file entirely, either move it away or use the -C option to
201 point <command>nbd-server</command>(1) to a non-existing or
202 empty configuration file.</para>
203 <para>Also note that if an empty, incomplete, or invalid
204 configuration file is specified, nbd-server will produce a
205 warning about failure to parse the config file. If the
206 command line contains a fully specified configuration, this
207 warning is harmless and may be ignored.</para>
211 <term><option>host list filename</option></term>
213 <para>This argument should contain a list of IP-addresses
214 for hosts that may connect to the server. Wildcards are
215 <emphasis>not</emphasis> allowed. If the file does not
216 exist, it is ignored (and any host can connect); If the file
217 does exist, but is empty, no host can connect. By default,
218 the name 'nbd_server.allow' is used, and looked for in the
219 current directory, unless nbd-server is compiled as a
220 daemon, in which case it is looked for in the
221 root-directory.</para>
225 <term><option>section name</option></term>
227 <para>If the <option>-o</option> argument is given on the
228 command line, then &dhpackage; will output a configuration
229 file section with this as the header that is functionally
230 equivalent to the other options specified on the command line,
231 and exit. This is useful for migrating pre-2.9 nbd-server
232 initscript configuration files to the new format.</para>
239 <title>EXAMPLES</title>
240 <para>Some examples of nbd-server usage:</para>
241 <itemizedlist mark="none">
243 <para>To export a file /export/nbd/exp-bl-dev on port 2000:</para>
244 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev</command></para>
247 <para>To export a the same file read-only:</para>
248 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev -r</command></para>
251 <para>To export the same file read-write, but make sure
252 changes are lost after restarting the client or the
254 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev
260 <title>SEE ALSO</title>
262 <para>nbd-client (8), nbd-server (5), http://nbd.sourceforge.net/roadmap.html</para>
266 <title>AUTHOR</title>
267 <para>The NBD kernel module and the NBD tools were originally
268 written by Pavel Machek (pavel@ucw.cz)</para>
270 <para>The Linux kernel module is now maintained by Paul Clements
271 (Paul.Clements@steeleye.com), while the userland tools are
272 maintained by &dhusername; (&dhemail;)</para>
274 <para>On The Hurd there is a regular translator available to perform the
275 client side of the protocol, and the use of
276 <command>nbd-client</command> is not required. Please see the
277 relevant documentation for more information.</para>
279 <para>This manual page was written by &dhusername; (&dhemail;) for
280 the &debian; system (but may be used by others). Permission is
281 granted to copy, distribute and/or modify this document under
282 the terms of the <acronym>GNU</acronym> General Public License,
283 version 2, as published by the Free Software Foundation.</para>