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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 "nbd_server.allow" in the current directory (by default; a different file can be chosen with the '-l' option).
86 This file must list the IP-addresses of clients that are allowed
87 to connect. If it does not exist, all clients are able to connect.
88 If the file is empty, no clients can connect.</para>
90 <para>Note that while the command line allows for specifying an
91 export, the use of this option is deprecated. It is preferred to
92 make use of a configuration file instead, the format of which is
93 defined in nbd-server(5).</para>
96 <title>OPTIONS</title>
102 <para>The ip address the server should listen on. This may
103 be an IPv4 address, an IPv6 address, or a hostname. In the
104 latter case, nbd-server will do a hostname lookup for the
105 name specified, and will listen on the first address that is
106 returned. For compatibility with past versions of
107 nbd-server, if an IPv4 address is specified, the @ sign that
108 serves as separator between the address and port may be
109 replaced by a colon.</para>
110 <para>If this parameter is not specified, nbd-server will
111 listen on all local addresses on both IPv4 and IPv6. To
112 limit to IPv4, specify the address as 0.0.0.0; to limit to
113 IPv6, specify it as ::.</para>
117 <term><option>port</option>
120 <para>The port the server should listen to. A valid port is
121 any number between 1 and 65536; if 0 is used, nbd-server
122 will listen on stdin (so that nbd-server can be ran from
127 <term><option>filename</option></term>
129 <para>The filename of the file that should be exported. This
130 can be any file, including "real" blockdevices (i.e. a file
131 from /dev). If the filename includes the literal string
132 "%s", then this %s will be substituded with the IP-address
133 of the client trying to connect.</para>
137 <term><option>size</option></term>
139 <para>The size of the block device at the client side. This
140 is especially usefull in conjunction with the -m
142 <para>Can optionally be followed by one of K,k,M or
143 m, in which case the size will be multiplied by 1024 (K
144 or k) or 1048576 (M or m)</para>
148 <term><option>-r</option></term>
150 <para>Export the file read-only. If a client tries to write
151 to a read-only exported file, it will receive an error, but
152 the connection will stay up.</para>
156 <term><option>-m</option></term>
158 <para>Work with multiple files. This can be used to export
159 blockdevices that are larger than the maximum allowed
160 filesize on a given filesystem; i.e. when the filesystem
161 does not allow files larger than 2GB (which is true for
162 Linux 2.2 and below), you can use this option to store the
163 data in multiple files and export a larger filesystem, if
166 To use this option, you must create a number of files
167 with names in the format "name.X", where "name" is given as
168 the filename argument to nbd-server, and "X" is a number
169 starting by 0 and going up for each file.
172 Allowing more flexibility for this option is planned for
173 future versions.</para>
177 <term><option>-c</option></term>
179 <para>Copy on write. When this option is provided,
180 write-operations are not done to the exported file, but to a
181 separate file. This separate file is removed when the
182 connection is closed, which means that serving this way will
183 make nbd-server slow down (especially on large block devices
184 with lots of writes), and that after disconnecting and
185 reconnecting the client or the server, all changes are
190 <term><option>-C</option></term>
192 <para>Specify configuration file. The default configuration
193 file, if this parameter is not specified, is
194 <filename>@sysconfdir@/nbd-server/config</filename>.</para>
195 <para>Note that the configuration file is always parsed and
196 the entries in the file used, even if an extra server is
197 specified on the command line. To disable the configuration
198 file entirely, either move it away or use the -C option to
199 point <command>nbd-server</command>(1) to a non-existing or
200 empty configuration file.</para>
201 <para>Also note that if an empty, incomplete, or invalid
202 configuration file is specified, nbd-server will produce a
203 warning about failure to parse the config file. If the
204 command line contains a fully specified configuration, this
205 warning is harmless and may be ignored.</para>
209 <term><option>host list filename</option></term>
211 <para>This argument should contain a list of IP-addresses
212 for hosts that may connect to the server. Wildcards are
213 <emphasis>not</emphasis> allowed. If the file does not
214 exist, it is ignored (and any host can connect); If the file
215 does exist, but is empty, no host can connect. By default,
216 the name 'nbd_server.allow' is used, and looked for in the
217 current directory, unless nbd-server is compiled as a
218 daemon, in which case it is looked for in the
219 root-directory.</para>
223 <term><option>section name</option></term>
225 <para>If the <option>-o</option> argument is given on the
226 command line, then &dhpackage; will output a configuration
227 file section with this as the header that is functionally
228 equivalent to the other options specified on the command line,
229 and exit. This is useful for migrating pre-2.9 nbd-server
230 initscript configuration files to the new format.</para>
237 <title>EXAMPLES</title>
238 <para>Some examples of nbd-server usage:</para>
239 <itemizedlist mark="none">
241 <para>To export a file /export/nbd/exp-bl-dev on port 2000:</para>
242 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev</command></para>
245 <para>To export a the same file read-only:</para>
246 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev -r</command></para>
249 <para>To export the same file read-write, but make sure
250 changes are lost after restarting the client or the
252 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev
258 <title>SEE ALSO</title>
260 <para>nbd-client (8), nbd-server (5), http://nbd.sourceforge.net/roadmap.html</para>
264 <title>AUTHOR</title>
265 <para>The NBD kernel module and the NBD tools were originally
266 written by Pavel Machek (pavel@ucw.cz)</para>
268 <para>The Linux kernel module is now maintained by Paul Clements
269 (Paul.Clements@steeleye.com), while the userland tools are
270 maintained by &dhusername; (&dhemail;)</para>
272 <para>On The Hurd there is a regular translator available to perform the
273 client side of the protocol, and the use of
274 <command>nbd-client</command> is not required. Please see the
275 relevant documentation for more information.</para>
277 <para>This manual page was written by &dhusername; (&dhemail;) for
278 the &debian; system (but may be used by others). Permission is
279 granted to copy, distribute and/or modify this document under
280 the terms of the <acronym>GNU</acronym> General Public License,
281 version 2, as published by the Free Software Foundation.</para>
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