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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>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>
71 <title>DESCRIPTION</title>
73 <para><command>&dhpackage;</command> is the server for the Linux
74 Network Block Device (NBD). With NBD, a client can use a file,
75 exported over the network from a server, as a block device. It can
76 then be used for whatever purpose a normal block device (harddisk,
77 CD-ROM, ...) can be used for.</para>
79 <para>NBD can be useful for diskless clients that need swapspace,
80 but you can also create a filesystem on it and use it as though it
81 were a local filesystem.</para>
83 <para><command>&dhpackage;</command> implements some security
84 through a file called "nbd_server.allow" in the current directory (by default; a different file can be chosen with the '-l' option).
85 This file must list the IP-addresses of clients that are allowed
86 to connect. If it does not exist, all clients are able to connect.
87 If the file is empty, no clients can connect.</para>
90 <title>OPTIONS</title>
94 <term><option>port</option>
97 <para>The port the server should listen to. A valid port is
98 any number between 1 and 65536; if 0 is used, nbd-server
99 will listen on stdin (so that nbd-server can be ran from
104 <term><option>filename</option></term>
106 <para>The filename of the file that should be exported. This
107 can be any file, including "real" blockdevices (i.e. a file
108 from /dev). If the filename includes the literal string
109 "%s", then this %s will be substituded with the IP-address
110 of the client trying to connect.</para>
114 <term><option>size</option></term>
116 <para>The size of the block device at the client side. This
117 is especially usefull in conjunction with the -m
119 <para>Can optionally be followed by one of K,k,M or
120 m, in which case the size will be multiplied by 1024 (K
121 or k) or 1048576 (M or m)</para>
125 <term><option>-r</option></term>
127 <para>Export the file read-only. If a client tries to write
128 to a read-only exported file, it will receive an error, but
129 the connection will stay up.</para>
133 <term><option>-m</option></term>
135 <para>Work with multiple files. This can be used to export
136 blockdevices that are larger than the maximum allowed
137 filesize on a given filesystem; i.e. when the filesystem
138 does not allow files larger than 2GB (which is true for
139 Linux 2.2 and below), you can use this option to store the
140 data in multiple files and export a larger filesystem, if
143 To use this option, you must create a number of files
144 with names in the format "name.X", where "name" is given as
145 the filename argument to nbd-server, and "X" is a number
146 starting by 0 and going up for each file.
149 The files must all be 1GB in size.
152 Allowing more flexibility for this option is planned for
153 future versions.</para>
157 <term><option>-c</option></term>
159 <para>Copy on write. When this option is provided,
160 write-operations are not done to the exported file, but to a
161 separate file. This separate file is removed when the
162 connection is closed, which means that serving this way will
163 make nbd-server slow down (especially on large block devices
164 with lots of writes), and that after disconnecting and
165 reconnecting the client or the server, all changes are
170 <term><option>-C</option></term>
172 <para>Specify configuration file. The default configuration
173 file, if this parameter is not specified, is
174 <filename>@sysconfdir@/nbd-server/config</filename>.</para>
175 <para>Note that the configuration file is always parsed and
176 the entries in the file used, even if an extra server is
177 specified on the command line. To disable the configuration
178 file entirely, either move it away or use the -C option to
179 point <command>nbd-server</command>(1) to a non-existing or
180 empty configuration file.</para>
184 <term><option>timeout</option></term>
186 <para>Maximum number of idle seconds. If a connection is
187 inactive for this amount of time, it is terminated; this is to
188 avoid stale nbd-server processes staying in memory. Use of
189 this option is strongly recommended.</para>
193 <term><option>host list</option></term>
195 <para>This argument should contain a list of IP-addresses
196 for hosts that may connect to the server. Wildcards are
197 <emphasis>not</emphasis> allowed. If the file does not
198 exist, it is ignored (and any host can connect); If the file
199 does exist, but is empty, no host can connect. By default,
200 the name 'nbd_server.allow' is used, and looked for in the
201 current directory, unless nbd-server is compiled as a
202 daemon, in which case it is looked for in the
203 root-directory.</para>
210 <title>EXAMPLES</title>
211 <para>Some examples of nbd-server usage:</para>
212 <itemizedlist mark="none">
214 <para>To export a file /export/nbd/exp-bl-dev on port 2000:</para>
215 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev</command></para>
218 <para>To export a the same file read-only:</para>
219 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev -r</command></para>
222 <para>To export the same file read-write, but make sure
223 changes are lost after restarting the client or the
225 <para><command>nbd-server 2000 /export/nbd/exp-bl-dev
231 <title>SEE ALSO</title>
233 <para>nbd-client (8), nbd-server (5), http://nbd.sourceforge.net/roadmap.html</para>
237 <title>AUTHOR</title>
238 <para>The NBD kernel module and the NBD tools were originally
239 written by Pavel Machek (pavel@ucw.cz)</para>
241 <para>The Linux kernel module is now maintained by Paul Clements
242 (Paul.Clements@steeleye.com), while the userland tools are
243 maintained by &dhusername; (&dhemail;)</para>
245 <para>On The Hurd there is a regular translator available to perform the
246 client side of the protocol, and the use of
247 <command>nbd-client</command> is not required. Please see the
248 relevant documentation for more information.</para>
250 <para>This manual page was written by &dhusername; (&dhemail;) for
251 the &debian; system (but may be used by others). Permission is
252 granted to copy, distribute and/or modify this document under
253 the terms of the <acronym>GNU</acronym> General Public License,
254 version 2, as published by the Free Software Foundation.</para>
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