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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
67 <filename>@sysconfdir@/nbd-server/config</filename> is the default
68 configuration file, this can be varied with the <option>-C</option>
69 option to <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.
149 <title>OPTIONS FOR EXPORT SECTIONS</title>
151 <!-- These are in alphabetical order, please keep it that way -->
154 <term><option>authfile</option></term>
157 Optional; string; default
158 <filename>@sysconfdir@/nbd-server/allow</filename>.
161 The name of the authorization file for this export. This
162 file should contain one line per IP-address, or per
163 network (which must be specified in CIDR-style
164 <option><replaceable>network</replaceable>/<replaceable>masklen</replaceable></option>)
165 and must not contain empty lines. If the file
166 does not exist, everyone is allowed to connect. If the
167 file exists but is empty, nobody is allowed to
168 connect. Otherwise, <command>nbd-server</command> will
169 only allow clients to connect whose IP-adres is listed in
172 <para>Corresponds to the <option>-l</option> option on the
177 <term><option>copyonwrite</option></term>
183 Whether this is a copy-on-write export. If it is, then any
184 writes to this export will not be written to the master
185 file, but to a separate file which will be removed upon
186 disconnect. The result of using this option is that
187 nbd-server will be slower, and that any writes will be
188 lost upon disconnect.
190 <para>Corresponds to the <option>-c</option> option on the
195 <term><option>exportname</option></term>
197 <para>Required; string.</para>
199 The name of the file (or block device) that will be
200 exported. This must be a fully-qualified path and filename;
201 relative paths are not allowed.
204 Note that <command>nbd-server</command> will only try to
205 find and open the exported file when a client actually
206 connects; as a result, <command>nbd-server</command> must
207 be able to open and read this file
208 <emphasis>after</emphasis> changing to the user and group
209 that have been specified by use of the
210 <option>user</option> and <option>group</option> options;
211 also, <command>nbd-server</command> will only detect
212 errors in this option upon connection of a client.
214 <para>When specified on the command line, this should be the
220 <term><option>filesize</option></term>
222 <para>Optional; integer; default autodetected.</para>
224 Disable autodetection of file or block device size, and
225 forcibly specify a size. Sizes must be specified in
226 bytes. If the <option>multifile</option> option is in
227 effect, this option specifies the size of the
228 <emphasis>entire</emphasis> export, not of individual
231 <para>When specified on the command line, this should be the
237 <term>listenaddr</term>
239 <para>Optional; string</para>
240 <para>If this option is set, it should contain the local IP
241 address on which we should listen to
242 <command>nbd-client</command>(8) connections. If it is not
243 set, <command>nbd-server</command> will listen to all
244 local IPv4 and IPv6 addresses. To limit to IPv6, specify the
245 address as "::". To limit to IPv4, specify as "0.0.0.0". It
246 is not possible to specify more than one IP address
251 <term><option>multifile</option></term>
253 <para>Optional; boolean.</para>
255 If this option is set to true, then
256 <command>nbd-server</command> will search for files of the
258 <replaceable>exportname</replaceable>.<replaceable>integer</replaceable>,
259 with <replaceable>exportname</replaceable> being the
260 filename that would otherwise have been used (after name
261 transformation for virtualization, if any, has been
262 performed) and <replaceable>integer</replaceable> an
263 integer number, starting with 0 and ending when no more
267 The size of the individual files will be autodetected,
268 <emphasis>even</emphasis> if the <option>filesize</option>
269 option has been specified. See the documentation for the
270 <option>multifile</option> for details.
273 Corresponds to the <option>-m</option> option on the
279 <term><option>port</option></term>
281 <para>Required; integer.</para>
283 The port on which this export is to be served. Currently
284 it is not possible to export multiple block devices on the
285 same port unless virtualization is used; future versions
286 of <command>nbd-server</command> may add this
290 When specified on the command line, this should be the
296 <term><option>readonly</option></term>
298 <para>Optional; boolean.</para>
300 Disallow writes to the device. If this option is
301 specified, <command>nbd-server</command> will issue an
302 error to any client that tries to write to the device.
305 Use of this option in conjunction with
306 <option>copyonwrite</option> is possible, but silly.
308 <para>Corresponds to the <option>-r</option> option on the
313 <term><option>sdp</option></term>
315 <para>Optional; boolean.</para>
317 When this option is enabled, <command>nbd-server</command>
318 will use the Socket Direct Protocol (SDP) to serve the
319 export, rather than just IP. This is faster, but requires
320 special hardware (usually something like InfiniBand) and
321 support in the kernel.
324 Additionally, support for this option must be enabled at
325 compile time, using the <option>--enable-sdp</option> option
326 to the <command>configure</command> script. If this option
327 is found in a configuration file and
328 <command>nbd-server</command> does not have support for SDP,
329 then <command>nbd-server</command> will exit with an error
335 <term><option>sync</option></term>
337 <para>Optional; boolean.</para>
338 <para>When this option is enabled,
339 <command>nbd-server</command> will call an fsync() after every
340 write to the backend storage. Calling fsync() increases
341 reliability in case of an unclean shutdown of nbd-server; but,
342 depending on the file system used on the nbd-server side, may
343 degrade performance. The use of this option isn't always
344 necessary; e.g., on ext3 filesystems, it is recommended that
345 it is <emphasis>not</emphasis> enabled, since it seriously
346 reduces performance on ext3 filesystems while not
347 importantly impacting reliability.
352 <term><option>sparse_cow</option></term>
354 <para>Optional; boolean.</para>
356 When this option is enabled, <command>nbd-server</command>
357 will use sparse files to implement the copy-on-write
358 option; such files take up less space then they appear to,
359 which allows <command>nbd-server</command> to handle the
360 file as if it was just as large as the block device it's
364 If this option is disabled, <command>nbd-server</command>
365 will map every newly written block to the end of the
366 copy-on-write file, which means that
367 <command>nbd-server</command> will have to lseek(2) to the
368 right position after every 4096-byte block.
371 Using this option may be faster when much is being written
377 <term><option>timeout</option></term>
379 <para>Optional; integer; default 0</para>
381 How many seconds a connection may be idle for this
382 export. When a connection is idle for a longer time,
383 <command>nbd-server</command> will forcibly disconnect the
384 connection. If you specify 0 (the default), then a
385 connection may be idle forever.
388 Corresponds to the <option>-a</option> option on the
394 <term><option>virtstyle</option></term>
396 <para>Optional; string; default "ipliteral"</para>
398 Defines the style of virtualization. Virtualization allows
399 one to create one export that will serve a different file
400 depending on the IP address that is connecting. When
401 virtualization is There are three types of virtualization
402 that <command>nbd-server</command> supports:
406 <term><option>none</option></term>
409 No virtualization. Will attempt to open the filename
410 as it was written, even if it contains '%s' in the
416 <term><option>ipliteral</option></term>
419 <command>nbd-server</command> will look for the
420 literal string '%s' in the
421 <option>exportname</option>, and replace it by the
422 address of the connecting host. The string that
423 results from this transformation will be used as an
424 absolute pathname that <command>nbd-server</command>
425 will attempt to open. As an example, if a client
426 connects from 192.168.1.100 and
427 <option>exportname</option> is specified as
428 <filename>/export/%s</filename>, then nbd-server
429 will attempt to serve
430 <filename>/export/192.168.1.100</filename>
435 <term><option>iphash</option></term>
438 Same as above, except that
439 <command>nbd-server</command> will replace the dots
440 in the IP address by forward slashes ('/'); in the
441 same example, <command>nbd-server</command> would
442 open <filename>/export/192/168/1/100</filename>
446 Since there are no dots in most IPv6 addresses, the
447 effect of using this option when IPv6 is in use is
448 indistinguishable from the ipliteral option.
453 <term><option>cidrhash</option></term>
456 This option requires one to add a space and a number
457 after it. <command>nbd-server</command> will use the
458 number as a network mask in CIDR style, and use that
459 as a hash cutoff point. In the above example, if
460 <option>virtstyle</option> has been specified as
461 <constant>cidrhash 16</constant>, then
462 <command>nbd-server</command> will try to open
463 <filename>/export/192.168.0.0/192.168.1.100</filename>;
464 if <option>virtstyle</option> were specified as
465 <constant>cidrhash 26</constant>, then
466 <command>nbd-server</command> will try to open
467 <filename>/export/192.168.1.64/192.168.1.100</filename>.
469 <para>This option works as expected for IPv6.</para>
476 <term><option>prerun</option></term>
478 <para>Optional; string</para>
480 If specified, then this command will be ran after a
481 client has connected to the server (and has been
482 accepted), but before the server starts serving. If
483 the command contains the literal string '%s', then
484 this string will be replaced by the filename of the
485 file which nbd-server wants to export.
488 This is useful to create export files on the fly, or
489 to verify that a file can be used for export, to
490 write something to a log file, or similar.
493 If the command runs with a non-zero exit status,
494 then nbd-server will assume the export will fail,
495 and refuse to serve it.
500 <term><option>postrun</option></term>
502 <para>Optional; string</para>
504 If specified, then it is assumed to be a command
505 that will be ran when a client has
506 disconnected. This can be useful to clean up
507 whatever <option>prerun</option> has set up, to log
508 something, or similar.
511 If the literal string '%s' is present in the
512 command, it will be replaced by the file name that
513 has just been closed.
516 In contrast to the <option>prerun</option> option,
517 the exit state of <option>postrun</option> is
518 <emphasis>ignored</emphasis>.
526 <title>SEE ALSO</title>
528 <para>nbd-server (1), nbd-client (8),
529 http://nbd.sourceforge.net/roadmap.html</para>
533 <title>AUTHOR</title>
534 <para>The NBD kernel module and the NBD tools were originally
535 written by Pavel Machek (pavel@ucw.cz)</para>
537 <para>The Linux kernel module is now maintained by Paul Clements
538 (Paul.Clements@steeleye.com), while the userland tools are
539 maintained by &dhusername; (&dhemail;)</para>
541 <para>On The Hurd there is a regular translator available to perform the
542 client side of the protocol, and the use of
543 <command>nbd-client</command> is not required. Please see the
544 relevant documentation for more information.</para>
546 <para>This manual page was written by &dhusername; (&dhemail;) for
547 the &debian; system (but may be used by others). Permission is
548 granted to copy, distribute and/or modify this document under
549 the terms of the <acronym>GNU</acronym> General Public License,
550 version 2, as published by the Free Software Foundation.</para>
554 <title>EXAMPLES</title>
555 <para>A simple <command>nbd-server</command> configuration file
556 would look like this:</para>
560 exportname = /export/blkdev
563 <para>For increased security, one might want to create an
564 authorization file, and set the UID and GID to run as:</para>
570 exportname = /export/blkdev
572 authfile = /etc/nbd-server/allow
574 <para>With /etc/nbd-server/allow containing the following:</para>
583 <!-- Keep this comment at the end of the file
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