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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>-a <replaceable>timeout</replaceable></option></arg>
67 <arg><option>-l <replaceable>host list</replaceable></option></arg>
68 <arg><option>-o <replaceable>section name</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>
91 <title>OPTIONS</title>
97 <para>The ip address the server should listen on. If
98 omitted, 0.0.0.0 (aka "any address") is used.</para>
102 <term><option>port</option>
105 <para>The port the server should listen to. A valid port is
106 any number between 1 and 65536; if 0 is used, nbd-server
107 will listen on stdin (so that nbd-server can be ran from
112 <term><option>filename</option></term>
114 <para>The filename of the file that should be exported. This
115 can be any file, including "real" blockdevices (i.e. a file
116 from /dev). If the filename includes the literal string
117 "%s", then this %s will be substituded with the IP-address
118 of the client trying to connect.</para>
122 <term><option>size</option></term>
124 <para>The size of the block device at the client side. This
125 is especially usefull in conjunction with the -m
127 <para>Can optionally be followed by one of K,k,M or
128 m, in which case the size will be multiplied by 1024 (K
129 or k) or 1048576 (M or m)</para>
133 <term><option>-r</option></term>
135 <para>Export the file read-only. If a client tries to write
136 to a read-only exported file, it will receive an error, but
137 the connection will stay up.</para>
141 <term><option>-m</option></term>
143 <para>Work with multiple files. This can be used to export
144 blockdevices that are larger than the maximum allowed
145 filesize on a given filesystem; i.e. when the filesystem
146 does not allow files larger than 2GB (which is true for
147 Linux 2.2 and below), you can use this option to store the
148 data in multiple files and export a larger filesystem, if
151 To use this option, you must create a number of files
152 with names in the format "name.X", where "name" is given as
153 the filename argument to nbd-server, and "X" is a number
154 starting by 0 and going up for each file.
157 The files must all be 1GB in size.
160 Allowing more flexibility for this option is planned for
161 future versions.</para>
165 <term><option>-c</option></term>
167 <para>Copy on write. When this option is provided,
168 write-operations are not done to the exported file, but to a
169 separate file. This separate file is removed when the
170 connection is closed, which means that serving this way will
171 make nbd-server slow down (especially on large block devices
172 with lots of writes), and that after disconnecting and
173 reconnecting the client or the server, all changes are
178 <term><option>-C</option></term>
180 <para>Specify configuration file. The default configuration
181 file, if this parameter is not specified, is
182 <filename>@sysconfdir@/nbd-server/config</filename>.</para>
183 <para>Note that the configuration file is always parsed and
184 the entries in the file used, even if an extra server is
185 specified on the command line. To disable the configuration
186 file entirely, either move it away or use the -C option to
187 point <command>nbd-server</command>(1) to a non-existing or
188 empty configuration file.</para>
192 <term><option>timeout</option></term>
194 <para>Maximum number of idle seconds. If a connection is
195 inactive for this amount of time, it is terminated; this is to
196 avoid stale nbd-server processes staying in memory. Use of
197 this option is strongly recommended.</para>
201 <term><option>host list</option></term>
203 <para>This argument should contain a list of IP-addresses
204 for hosts that may connect to the server. Wildcards are
205 <emphasis>not</emphasis> allowed. If the file does not
206 exist, it is ignored (and any host can connect); If the file
207 does exist, but is empty, no host can connect. By default,
208 the name 'nbd_server.allow' is used, and looked for in the
209 current directory, unless nbd-server is compiled as a
210 daemon, in which case it is looked for in the
211 root-directory.</para>
215 <term><option>section name</option></term>
217 <para>If the <option>-o</option> argument is given on the
218 command line, then &dhpackage; will output a configuration
219 file section with this as the header that is functionally
220 equivalent to the other options specified on the command line,
221 and exit. This is useful for migrating pre-2.9 nbd-server
222 initscript configuration files to the new format.</para>
229 <title>EXAMPLES</title>
230 <para>Some examples of nbd-server usage:</para>
231 <itemizedlist mark="none">
233 <para>To export a file /export/nbd/exp-bl-dev on port 2000:</para>
234 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev</command></para>
237 <para>To export a the same file read-only:</para>
238 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev -r</command></para>
241 <para>To export the same file read-write, but make sure
242 changes are lost after restarting the client or the
244 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev
250 <title>SEE ALSO</title>
252 <para>nbd-client (8), nbd-server (5), http://nbd.sourceforge.net/roadmap.html</para>
256 <title>AUTHOR</title>
257 <para>The NBD kernel module and the NBD tools were originally
258 written by Pavel Machek (pavel@ucw.cz)</para>
260 <para>The Linux kernel module is now maintained by Paul Clements
261 (Paul.Clements@steeleye.com), while the userland tools are
262 maintained by &dhusername; (&dhemail;)</para>
264 <para>On The Hurd there is a regular translator available to perform the
265 client side of the protocol, and the use of
266 <command>nbd-client</command> is not required. Please see the
267 relevant documentation for more information.</para>
269 <para>This manual page was written by &dhusername; (&dhemail;) for
270 the &debian; system (but may be used by others). Permission is
271 granted to copy, distribute and/or modify this document under
272 the terms of the <acronym>GNU</acronym> General Public License,
273 version 2, as published by the Free Software Foundation.</para>
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