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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: 2006-10-18 15:01:57 +0200 (wo, 18 okt 2006) $</date>">
17 <!-- SECTION should be 1-8, maybe w/ subsection other parameters are
18 allowed: see man(7), man(1). -->
19 <!ENTITY dhsection "<manvolnum>5</manvolnum>">
20 <!ENTITY dhemail "<email>wouter@debian.org</email>">
21 <!ENTITY dhusername "Wouter Verhelst">
22 <!ENTITY dhucpackage "<refentrytitle>NBD-SERVER</refentrytitle>">
23 <!ENTITY dhpackage "/etc/nbd-server/config">
25 <!ENTITY debian "<productname>Debian GNU/Linux</productname>">
26 <!ENTITY gnu "<acronym>GNU</acronym>">
40 <holder>&dhusername;</holder>
50 <refname>&dhpackage;</refname>
52 <refpurpose>configuration file for nbd-server</refpurpose>
56 <command>&dhpackage; </command>
61 <title>DESCRIPTION</title>
63 <para><command>&dhpackage;</command> allows to configure the
66 <para>The default configuration file is
67 <filename>@sysconfdir@/nbd-server/config</filename>, but this
68 can be varied with the <option>-C</option> option to
69 <command>nbd-server</command>(1).
72 The configuration file consists of section header lines, comment
73 lines, and option lines.
76 A section header is a unique name that
77 is enclosed in square brackets ("[" and "]"). A section header
78 denotes the beginning of a section; a section continues until
79 the next section or the end of the file, whichever is first. The
80 first section in the configuration file must be called
81 <option>generic</option>, and is used for global options that
82 apply to more than one export. This section must always be
83 present, even if it holds no options. Every other section
84 defines one export; the names of these sections are not
85 important, except that you should take care to make sure that
86 each section name is unique (future versions of
87 <command>nbd-server</command> may use the section name to refer
91 A comment line is a line that starts with optional whitespace,
92 followed by a pound sign ("#"), and continues until the end of
93 the line. Comments may <emphasis>not</emphasis> be used on
94 option lines or section header lines.
97 An option line is a line that starts with an option name,
98 followed by an equals sign ("="), followed by the option
99 value. An option can be of type string, of type integer, or of
100 type boolean. The value of a boolean option can be denoted with
101 either true or false (so not yes, no, on, off, 1, or 0); all
102 booleans default to false unless specified otherwise; no value
103 may be quoted (always enter it directly); for a string option,
104 leading whitespace is stripped (but trailing whitespace is not).
109 <title>OPTIONS FOR SECTION [generic]</title>
111 <!-- These are in alphabetical order, please keep it that way -->
114 <term><option>group</option></term>
120 The name of the group this server must run as. If this
121 parameter is not specified, then nbd-server will not
122 attempt to change its GID (so the GID it runs as will be
123 the primary group of the user who starts nbd-server). If
124 it is specified, then nbd-server will change its GID after
125 opening ports, but before accepting connections or opening
131 <term><option>user</option></term>
137 The name of the user this server must run as. If this
138 parameter is not specified, then nbd-server will not
139 attempt to change its UID (so the UID it runs as will be
140 the user who starts nbd-server). If it is specified, then
141 nbd-server will change its UID after opening ports, but
142 before accepting connections or opening files.
148 <title>OPTIONS FOR EXPORT SECTIONS</title>
150 <!-- These are in alphabetical order, please keep it that way -->
153 <term><option>authfile</option></term>
156 Optional; string; default
157 <filename>@sysconfdir@/nbd-server/allow</filename>.
160 The name of the authorization file for this export. This
161 file should contain one line per IP-address, or per
162 network (which must be specified in CIDR-style
163 <option><replaceable>network</replaceable>/<replaceable>masklen</replaceable></option>)
164 and must not contain empty lines. If the file
165 does not exist, everyone is allowed to connect. If the
166 file exists but is empty, nobody is allowed to
167 connect. Otherwise, <command>nbd-server</command> will
168 only allow clients to connect whose IP-adres is listed in
171 <para>Corresponds to the <option>-l</option> option on the
176 <term><option>autoreadonly</option></term>
178 <para>Optional; boolean.</para>
180 If this option is set to true, then
181 <command>nbd-server</command> will automatically switch to
182 readonly if it cannot write to the file.
184 <para>Does not have a corresponding command-line
186 <para>TODO: verify whether this option actually works as
187 documented. I have a feeling I've been terribly
193 <term><option>copyonwrite</option></term>
199 Whether this is a copy-on-write export. If it is, then any
200 writes to this export will not be written to the master
201 file, but to a separate file which will be removed upon
202 disconnect. The result of using this option is that
203 nbd-server will be slower, and that any writes will be
204 lost upon disconnect.
206 <para>Corresponds to the <option>-c</option> option on the
211 <term><option>exportname</option></term>
213 <para>Required; string.</para>
215 The name of the file that will be exported. This must be a
216 fully-qualified path and filename; relative paths are not
220 Note that <command>nbd-server</command> will only try to
221 find and open the exported file when a client actually
222 connects; as a result, <command>nbd-server</command> must
223 be able to open and read this file
224 <emphasis>after</emphasis> changing to the user and group
225 that have been specified by use of the
226 <option>user</option> and <option>group</option> options;
227 also, <command>nbd-server</command> will only detect
228 errors in this option upon connection of a client.
230 <para>When specified on the command line, this should be the
236 <term><option>filesize</option></term>
238 <para>Optional; integer; default autodetected.</para>
240 Disable autodetection of file or block device size, and
241 forcibly specify a size. Sizes must be specified in
242 bytes. If the <option>multifile</option> option is in
243 effect, this option specifies the size of the
244 <emphasis>entire</emphasis> export, not of individual
247 <para>When specified on the command line, this should be the
253 <term><option>multifile</option></term>
255 <para>Optional; boolean.</para>
257 If this option is set to true, then
258 <command>nbd-server</command> will search for files of the
260 <replaceable>exportname</replaceable>.<replaceable>integer</replaceable>,
261 with <replaceable>exportname</replaceable> being the
262 filename that would otherwise have been used (after
263 name transformation for virtualization, if any, has been
264 performed) and <replaceable>integer</replaceable> an
265 integer number, starting with 0 and ending when no more
269 The size of the individual files will be autodetected,
270 <emphasis>even</emphasis> if the <option>filesize</option>
271 option has been specified. See the documentation for the
272 <option>multifile</option> for details.
275 Corresponds to the <option>-m</option> option on the
281 <term><option>port</option></term>
283 <para>Required; integer.</para>
285 The port on which this export is to be served. Currently
286 it is not possible to export multiple block devices on the
287 same port unless virtualization is used; future versions
288 of <command>nbd-server</command> may add this
292 When specified on the command line, this should be the
298 <term><option>readonly</option></term>
300 <para>Optional; boolean.</para>
302 Disallow writes to the device. If this option is
303 specified, <command>nbd-server</command> will issue an
304 error to any client that tries to write to the device.
307 Use of this option in conjunction with
308 <option>copyonwrite</option> is possible, but silly.
310 <para>Corresponds to the <option>-r</option> option on the
315 <term><option>sparse_cow</option></term>
317 <para>Optional; boolean.</para>
319 When this option is enabled, <command>nbd-server</command>
320 will use sparse files to implement the copy-on-write
321 option; such files take up less space then they appear to,
322 which allows <command>nbd-server</command> to handle the
323 file as if it was just as large as the block device it's
327 If this option is disabled, <command>nbd-server</command>
328 will map every newly written block to the end of the
329 copy-on-write file, which means that
330 <command>nbd-server</command> will have to lseek(2) to the
331 right position after every 4096-byte block.
334 Using this option may be faster when much is being written
340 <term><option>timeout</option></term>
342 <para>Optional; integer; default 0</para>
344 How many seconds a connection may be idle for this
345 export. When a connection is idle for a longer time,
346 <command>nbd-server</command> will forcibly disconnect the
347 connection. If you specify 0 (the default), then a
348 connection may be idle forever.
351 Corresponds to the <option>-a</option> option on the
357 <term><option>virtstyle</option></term>
359 <para>Optional; string; default "ipliteral"</para>
361 Defines the style of virtualization. Virtualization allows
362 one to create one export that will serve a different file
363 depending on the IP address that is connecting. When
364 virtualization is There are three types of virtualization
365 that <command>nbd-server</command> supports:
369 <term><option>none</option></term>
372 No virtualization. Will attempt to open the filename
373 as it was written, even if it contains '%s' in the
379 <term><option>ipliteral</option></term>
382 <command>nbd-server</command> will look for the
383 literal string '%s' in the
384 <option>exportname</option>, and replace it by the
385 IP address of the connecting host in dotted-quad
386 notation. The string that results from this
387 transformation will be used as an absolute pathname
388 that <command>nbd-server</command> will attempt to
389 open. As an example, if a client connects from
390 192.168.1.100 and <option>exportname</option> is
391 specified as <filename>/export/%s</filename>, then
392 nbd-server will attempt to serve
393 <filename>/export/192.168.1.100</filename>
398 <term><option>iphash</option></term>
401 Same as above, except that
402 <command>nbd-server</command> will replace the dots
403 in the IP address by forward slashes ('/'); in the
404 same example, <command>nbd-server</command> would
405 open <filename>/export/192/168/1/100</filename>
411 <term><option>cidrhash</option></term>
414 This option requires one to add a space and a number
415 after it. <command>nbd-server</command> will use the
416 number as a network mask in CIDR style, and use that
417 as a hash cutoff point. In the above example, if
418 <option>virtstyle</option> has been specified as
419 <constant>cidrhash 16</constant>, then
420 <command>nbd-server</command> will try to open
421 <filename>/export/192.168.0.0/192.168.1.100</filename>;
422 if <option>virtstyle</option> were specified as
423 <constant>cidrhash 26</constant>, then
424 <command>nbd-server</command> will try to open
425 <filename>/export/192.168.1.64/192.168.1.100</filename>.
430 <term><option>prerun</option></term>
432 <para>Optional; string</para>
434 If specified, then this command will be ran after a
435 client has connected to the server (and has been
436 accepted), but before the server starts serving. If
437 the command contains the literal string '%s', then
438 this string will be replaced by the filename of the
439 file which nbd-server wants to export.
442 This is useful to create export files on the fly, or
443 to verify that a file can be used for export, to
444 write something to a log file, or similar.
447 If the command runs with a non-zero exit status,
448 then nbd-server will assume the export will fail,
449 and refuse to serve it.
454 <term><option>postrun</option></term>
456 <para>Optional; string</para>
458 If specified, then it is assumed to be a command
459 that will be ran when a client has
460 disconnected. This can be useful to clean up
461 whatever <option>prerun</option> has set up, to log
462 something, or similar.
465 If the literal string '%s' is present in the
466 command, it will be replaced by the file name that
467 has just been closed.
470 In contrast to the <option>prerun</option> option,
471 the exit state of <option>postrun</option> is
472 <emphasis>ignored</emphasis>.
483 <title>SEE ALSO</title>
485 <para>nbd-server (1), nbd-client (8),
486 http://nbd.sourceforge.net/roadmap.html</para>
490 <title>AUTHOR</title>
491 <para>The NBD kernel module and the NBD tools were originally
492 written by Pavel Machek (pavel@ucw.cz)</para>
494 <para>The Linux kernel module is now maintained by Paul Clements
495 (Paul.Clements@steeleye.com), while the userland tools are
496 maintained by &dhusername; (&dhemail;)</para>
498 <para>On The Hurd there is a regular translator available to perform the
499 client side of the protocol, and the use of
500 <command>nbd-client</command> is not required. Please see the
501 relevant documentation for more information.</para>
503 <para>This manual page was written by &dhusername; (&dhemail;) for
504 the &debian; system (but may be used by others). Permission is
505 granted to copy, distribute and/or modify this document under
506 the terms of the <acronym>GNU</acronym> General Public License,
507 version 2, as published by the Free Software Foundation.</para>
511 <title>EXAMPLES</title>
512 <para>A simple <command>nbd-server</command> configuration file
513 would look like this:</para>
517 exportname = /export/blkdev
520 <para>For increased security, one might want to create an
521 authorization file, and set the UID and GID to run as:</para>
527 exportname = /export/blkdev
529 authfile = /etc/nbd-server/allow
531 <para>With /etc/nbd-server/allow containing the following:</para>
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