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42 <div class="refentry" lang="en">
43 <a name="man.nsupdate"></a><div class="titlepage"></div>
44 <div class="refnamediv">
46 <p><span class="application">nsupdate</span> — Dynamic DNS update utility</p>
48 <div class="refsynopsisdiv">
50 <div class="cmdsynopsis"><p><code class="command">nsupdate</code> [<code class="option">-d</code>] [<code class="option">-D</code>] [[<code class="option">-g</code>] | [<code class="option">-o</code>] | [<code class="option">-l</code>] | [<code class="option">-y <em class="replaceable"><code>[<span class="optional">hmac:</span>]keyname:secret</code></em></code>] | [<code class="option">-k <em class="replaceable"><code>keyfile</code></em></code>]] [<code class="option">-t <em class="replaceable"><code>timeout</code></em></code>] [<code class="option">-u <em class="replaceable"><code>udptimeout</code></em></code>] [<code class="option">-r <em class="replaceable"><code>udpretries</code></em></code>] [<code class="option">-R <em class="replaceable"><code>randomdev</code></em></code>] [<code class="option">-v</code>] [filename]</p></div>
52 <div class="refsect1" lang="en">
53 <a name="id2639154"></a><h2>DESCRIPTION</h2>
54 <p><span><strong class="command">nsupdate</strong></span>
55 is used to submit Dynamic DNS Update requests as defined in RFC 2136
57 This allows resource records to be added or removed from a zone
58 without manually editing the zone file.
59 A single update request can contain requests to add or remove more than
64 Zones that are under dynamic control via
65 <span><strong class="command">nsupdate</strong></span>
66 or a DHCP server should not be edited by hand.
68 conflict with dynamic updates and cause data to be lost.
71 The resource records that are dynamically added or removed with
72 <span><strong class="command">nsupdate</strong></span>
73 have to be in the same zone.
74 Requests are sent to the zone's master server.
75 This is identified by the MNAME field of the zone's SOA record.
79 <code class="option">-d</code>
81 <span><strong class="command">nsupdate</strong></span>
82 operate in debug mode.
83 This provides tracing information about the update requests that are
84 made and the replies received from the name server.
87 The <code class="option">-D</code> option makes <span><strong class="command">nsupdate</strong></span>
88 report additional debugging information to <code class="option">-d</code>.
91 The <code class="option">-L</code> option with an integer argument of zero or
92 higher sets the logging debug level. If zero, logging is disabled.
95 Transaction signatures can be used to authenticate the Dynamic
96 DNS updates. These use the TSIG resource record type described
97 in RFC 2845 or the SIG(0) record described in RFC 2535 and
98 RFC 2931 or GSS-TSIG as described in RFC 3645. TSIG relies on
99 a shared secret that should only be known to
100 <span><strong class="command">nsupdate</strong></span> and the name server. Currently,
101 the only supported encryption algorithm for TSIG is HMAC-MD5,
102 which is defined in RFC 2104. Once other algorithms are
103 defined for TSIG, applications will need to ensure they select
104 the appropriate algorithm as well as the key when authenticating
105 each other. For instance, suitable <span class="type">key</span> and
106 <span class="type">server</span> statements would be added to
107 <code class="filename">/etc/named.conf</code> so that the name server
108 can associate the appropriate secret key and algorithm with
109 the IP address of the client application that will be using
110 TSIG authentication. SIG(0) uses public key cryptography.
111 To use a SIG(0) key, the public key must be stored in a KEY
112 record in a zone served by the name server.
113 <span><strong class="command">nsupdate</strong></span> does not read
114 <code class="filename">/etc/named.conf</code>.
117 GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode
118 is switched on with the <code class="option">-g</code> flag. A
119 non-standards-compliant variant of GSS-TSIG used by Windows
120 2000 can be switched on with the <code class="option">-o</code> flag.
122 <p><span><strong class="command">nsupdate</strong></span>
123 uses the <code class="option">-y</code> or <code class="option">-k</code> option
124 to provide the shared secret needed to generate a TSIG record
125 for authenticating Dynamic DNS update requests, default type
126 HMAC-MD5. These options are mutually exclusive.
129 When the <code class="option">-y</code> option is used, a signature is
131 [<span class="optional"><em class="parameter"><code>hmac:</code></em></span>]<em class="parameter"><code>keyname:secret.</code></em>
132 <em class="parameter"><code>keyname</code></em> is the name of the key, and
133 <em class="parameter"><code>secret</code></em> is the base64 encoded shared secret.
134 Use of the <code class="option">-y</code> option is discouraged because the
135 shared secret is supplied as a command line argument in clear text.
136 This may be visible in the output from
137 <span class="citerefentry"><span class="refentrytitle">ps</span>(1)</span>
138 or in a history file maintained by the user's shell.
142 <code class="option">-k</code> option, <span><strong class="command">nsupdate</strong></span> reads
143 the shared secret from the file <em class="parameter"><code>keyfile</code></em>.
144 Keyfiles may be in two formats: a single file containing
145 a <code class="filename">named.conf</code>-format <span><strong class="command">key</strong></span>
146 statement, which may be generated automatically by
147 <span><strong class="command">ddns-confgen</strong></span>, or a pair of files whose names are
148 of the format <code class="filename">K{name}.+157.+{random}.key</code> and
149 <code class="filename">K{name}.+157.+{random}.private</code>, which can be
150 generated by <span><strong class="command">dnssec-keygen</strong></span>.
151 The <code class="option">-k</code> may also be used to specify a SIG(0) key used
152 to authenticate Dynamic DNS update requests. In this case, the key
153 specified is not an HMAC-MD5 key.
156 <span><strong class="command">nsupdate</strong></span> can be run in a local-host only mode
157 using the <code class="option">-l</code> flag. This sets the server address to
158 localhost (disabling the <span><strong class="command">server</strong></span> so that the server
159 address cannot be overridden). Connections to the local server will
160 use a TSIG key found in <code class="filename">/var/run/named/session.key</code>,
161 which is automatically generated by <span><strong class="command">named</strong></span> if any
162 local master zone has set <span><strong class="command">update-policy</strong></span> to
163 <span><strong class="command">local</strong></span>. The location of this key file can be
164 overridden with the <code class="option">-k</code> option.
167 By default, <span><strong class="command">nsupdate</strong></span>
168 uses UDP to send update requests to the name server unless they are too
169 large to fit in a UDP request in which case TCP will be used.
171 <code class="option">-v</code>
173 <span><strong class="command">nsupdate</strong></span>
174 use a TCP connection.
175 This may be preferable when a batch of update requests is made.
178 The <code class="option">-p</code> sets the default port number to use for
179 connections to a name server. The default is 53.
182 The <code class="option">-t</code> option sets the maximum time an update request
184 take before it is aborted. The default is 300 seconds. Zero can be
186 to disable the timeout.
189 The <code class="option">-u</code> option sets the UDP retry interval. The default
191 3 seconds. If zero, the interval will be computed from the timeout
193 and number of UDP retries.
196 The <code class="option">-r</code> option sets the number of UDP retries. The
198 3. If zero, only one update request will be made.
201 The <code class="option">-R <em class="replaceable"><code>randomdev</code></em></code> option
202 specifies a source of randomness. If the operating system
203 does not provide a <code class="filename">/dev/random</code> or
204 equivalent device, the default source of randomness is keyboard
205 input. <code class="filename">randomdev</code> specifies the name of
206 a character device or file containing random data to be used
207 instead of the default. The special value
208 <code class="filename">keyboard</code> indicates that keyboard input
209 should be used. This option may be specified multiple times.
212 <div class="refsect1" lang="en">
213 <a name="id2639897"></a><h2>INPUT FORMAT</h2>
214 <p><span><strong class="command">nsupdate</strong></span>
216 <em class="parameter"><code>filename</code></em>
218 Each command is supplied on exactly one line of input.
219 Some commands are for administrative purposes.
220 The others are either update instructions or prerequisite checks on the
221 contents of the zone.
222 These checks set conditions that some name or set of
223 resource records (RRset) either exists or is absent from the zone.
224 These conditions must be met if the entire update request is to succeed.
225 Updates will be rejected if the tests for the prerequisite conditions
229 Every update request consists of zero or more prerequisites
230 and zero or more updates.
231 This allows a suitably authenticated update request to proceed if some
232 specified resource records are present or missing from the zone.
233 A blank input line (or the <span><strong class="command">send</strong></span> command)
235 accumulated commands to be sent as one Dynamic DNS update request to the
239 The command formats and their meaning are as follows:
241 <div class="variablelist"><dl>
242 <dt><span class="term">
243 <span><strong class="command">server</strong></span>
248 Sends all dynamic update requests to the name server
249 <em class="parameter"><code>servername</code></em>.
250 When no server statement is provided,
251 <span><strong class="command">nsupdate</strong></span>
252 will send updates to the master server of the correct zone.
253 The MNAME field of that zone's SOA record will identify the
255 server for that zone.
256 <em class="parameter"><code>port</code></em>
257 is the port number on
258 <em class="parameter"><code>servername</code></em>
259 where the dynamic update requests get sent.
260 If no port number is specified, the default DNS port number of
264 <dt><span class="term">
265 <span><strong class="command">local</strong></span>
270 Sends all dynamic update requests using the local
271 <em class="parameter"><code>address</code></em>.
273 When no local statement is provided,
274 <span><strong class="command">nsupdate</strong></span>
275 will send updates using an address and port chosen by the
277 <em class="parameter"><code>port</code></em>
278 can additionally be used to make requests come from a specific
280 If no port number is specified, the system will assign one.
282 <dt><span class="term">
283 <span><strong class="command">zone</strong></span>
287 Specifies that all updates are to be made to the zone
288 <em class="parameter"><code>zonename</code></em>.
290 <em class="parameter"><code>zone</code></em>
291 statement is provided,
292 <span><strong class="command">nsupdate</strong></span>
293 will attempt determine the correct zone to update based on the
296 <dt><span class="term">
297 <span><strong class="command">class</strong></span>
301 Specify the default class.
302 If no <em class="parameter"><code>class</code></em> is specified, the
304 <em class="parameter"><code>IN</code></em>.
306 <dt><span class="term">
307 <span><strong class="command">ttl</strong></span>
311 Specify the default time to live for records to be added.
312 The value <em class="parameter"><code>none</code></em> will clear the default
315 <dt><span class="term">
316 <span><strong class="command">key</strong></span>
321 Specifies that all updates are to be TSIG-signed using the
322 <em class="parameter"><code>keyname</code></em> <em class="parameter"><code>keysecret</code></em> pair.
323 The <span><strong class="command">key</strong></span> command
324 overrides any key specified on the command line via
325 <code class="option">-y</code> or <code class="option">-k</code>.
327 <dt><span class="term">
328 <span><strong class="command">gsstsig</strong></span>
331 Use GSS-TSIG to sign the updated. This is equivalent to
332 specifying <code class="option">-g</code> on the commandline.
334 <dt><span class="term">
335 <span><strong class="command">oldgsstsig</strong></span>
338 Use the Windows 2000 version of GSS-TSIG to sign the updated.
339 This is equivalent to specifying <code class="option">-o</code> on the
342 <dt><span class="term">
343 <span><strong class="command">realm</strong></span>
344 {[<span class="optional">realm_name</span>]}
347 When using GSS-TSIG use <em class="parameter"><code>realm_name</code></em> rather
348 than the default realm in <code class="filename">krb5.conf</code>. If no
349 realm is specified the saved realm is cleared.
351 <dt><span class="term">
352 <span><strong class="command">prereq nxdomain</strong></span>
356 Requires that no resource record of any type exists with name
357 <em class="parameter"><code>domain-name</code></em>.
359 <dt><span class="term">
360 <span><strong class="command">prereq yxdomain</strong></span>
365 <em class="parameter"><code>domain-name</code></em>
366 exists (has as at least one resource record, of any type).
368 <dt><span class="term">
369 <span><strong class="command">prereq nxrrset</strong></span>
375 Requires that no resource record exists of the specified
376 <em class="parameter"><code>type</code></em>,
377 <em class="parameter"><code>class</code></em>
379 <em class="parameter"><code>domain-name</code></em>.
381 <em class="parameter"><code>class</code></em>
382 is omitted, IN (internet) is assumed.
384 <dt><span class="term">
385 <span><strong class="command">prereq yxrrset</strong></span>
391 This requires that a resource record of the specified
392 <em class="parameter"><code>type</code></em>,
393 <em class="parameter"><code>class</code></em>
395 <em class="parameter"><code>domain-name</code></em>
398 <em class="parameter"><code>class</code></em>
399 is omitted, IN (internet) is assumed.
401 <dt><span class="term">
402 <span><strong class="command">prereq yxrrset</strong></span>
410 <em class="parameter"><code>data</code></em>
411 from each set of prerequisites of this form
413 <em class="parameter"><code>type</code></em>,
414 <em class="parameter"><code>class</code></em>,
416 <em class="parameter"><code>domain-name</code></em>
417 are combined to form a set of RRs. This set of RRs must
418 exactly match the set of RRs existing in the zone at the
420 <em class="parameter"><code>type</code></em>,
421 <em class="parameter"><code>class</code></em>,
423 <em class="parameter"><code>domain-name</code></em>.
425 <em class="parameter"><code>data</code></em>
426 are written in the standard text representation of the resource
430 <dt><span class="term">
431 <span><strong class="command">update delete</strong></span>
438 Deletes any resource records named
439 <em class="parameter"><code>domain-name</code></em>.
441 <em class="parameter"><code>type</code></em>
443 <em class="parameter"><code>data</code></em>
444 is provided, only matching resource records will be removed.
445 The internet class is assumed if
446 <em class="parameter"><code>class</code></em>
448 <em class="parameter"><code>ttl</code></em>
449 is ignored, and is only allowed for compatibility.
451 <dt><span class="term">
452 <span><strong class="command">update add</strong></span>
460 Adds a new resource record with the specified
461 <em class="parameter"><code>ttl</code></em>,
462 <em class="parameter"><code>class</code></em>
464 <em class="parameter"><code>data</code></em>.
466 <dt><span class="term">
467 <span><strong class="command">show</strong></span>
470 Displays the current message, containing all of the
472 updates specified since the last send.
474 <dt><span class="term">
475 <span><strong class="command">send</strong></span>
478 Sends the current message. This is equivalent to entering a
481 <dt><span class="term">
482 <span><strong class="command">answer</strong></span>
487 <dt><span class="term">
488 <span><strong class="command">debug</strong></span>
497 Lines beginning with a semicolon are comments and are ignored.
500 <div class="refsect1" lang="en">
501 <a name="id2678629"></a><h2>EXAMPLES</h2>
503 The examples below show how
504 <span><strong class="command">nsupdate</strong></span>
505 could be used to insert and delete resource records from the
506 <span class="type">example.com</span>
508 Notice that the input in each example contains a trailing blank line so
510 a group of commands are sent as one dynamic update request to the
511 master name server for
512 <span class="type">example.com</span>.
515 <pre class="programlisting">
517 > update delete oldhost.example.com A
518 > update add newhost.example.com 86400 A 172.16.1.1
525 <span class="type">oldhost.example.com</span>
528 <span class="type">newhost.example.com</span>
529 with IP address 172.16.1.1 is added.
530 The newly-added record has a 1 day TTL (86400 seconds).
532 <pre class="programlisting">
534 > prereq nxdomain nickname.example.com
535 > update add nickname.example.com 86400 CNAME somehost.example.com
541 The prerequisite condition gets the name server to check that there
542 are no resource records of any type for
543 <span class="type">nickname.example.com</span>.
545 If there are, the update request fails.
546 If this name does not exist, a CNAME for it is added.
547 This ensures that when the CNAME is added, it cannot conflict with the
548 long-standing rule in RFC 1034 that a name must not exist as any other
549 record type if it exists as a CNAME.
550 (The rule has been updated for DNSSEC in RFC 2535 to allow CNAMEs to have
551 RRSIG, DNSKEY and NSEC records.)
554 <div class="refsect1" lang="en">
555 <a name="id2678679"></a><h2>FILES</h2>
556 <div class="variablelist"><dl>
557 <dt><span class="term"><code class="constant">/etc/resolv.conf</code></span></dt>
559 used to identify default name server
561 <dt><span class="term"><code class="constant">/var/run/named/session.key</code></span></dt>
563 sets the default TSIG key for use in local-only mode
565 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.key</code></span></dt>
567 base-64 encoding of HMAC-MD5 key created by
568 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
570 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.private</code></span></dt>
572 base-64 encoding of HMAC-MD5 key created by
573 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
577 <div class="refsect1" lang="en">
578 <a name="id2678762"></a><h2>SEE ALSO</h2>
580 <em class="citetitle">RFC 2136</em>,
581 <em class="citetitle">RFC 3007</em>,
582 <em class="citetitle">RFC 2104</em>,
583 <em class="citetitle">RFC 2845</em>,
584 <em class="citetitle">RFC 1034</em>,
585 <em class="citetitle">RFC 2535</em>,
586 <em class="citetitle">RFC 2931</em>,
587 <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>,
588 <span class="citerefentry"><span class="refentrytitle">ddns-confgen</span>(8)</span>,
589 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
592 <div class="refsect1" lang="en">
593 <a name="id2678820"></a><h2>BUGS</h2>
595 The TSIG key is redundantly stored in two separate files.
596 This is a consequence of nsupdate using the DST library
597 for its cryptographic operations, and may change in future
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