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24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
25 <a name="man.nsupdate"></a><div class="titlepage"></div>
26 <div class="refnamediv">
28 <p><span class="application">nsupdate</span> — Dynamic DNS update utility</p>
30 <div class="refsynopsisdiv">
32 <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">-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>
34 <div class="refsect1" lang="en">
35 <a name="id2543449"></a><h2>DESCRIPTION</h2>
36 <p><span><strong class="command">nsupdate</strong></span>
37 is used to submit Dynamic DNS Update requests as defined in RFC2136
39 This allows resource records to be added or removed from a zone
40 without manually editing the zone file.
41 A single update request can contain requests to add or remove more than
46 Zones that are under dynamic control via
47 <span><strong class="command">nsupdate</strong></span>
48 or a DHCP server should not be edited by hand.
50 conflict with dynamic updates and cause data to be lost.
53 The resource records that are dynamically added or removed with
54 <span><strong class="command">nsupdate</strong></span>
55 have to be in the same zone.
56 Requests are sent to the zone's master server.
57 This is identified by the MNAME field of the zone's SOA record.
61 <code class="option">-d</code>
63 <span><strong class="command">nsupdate</strong></span>
64 operate in debug mode.
65 This provides tracing information about the update requests that are
66 made and the replies received from the name server.
69 The <code class="option">-D</code> option makes <span><strong class="command">nsupdate</strong></span>
70 report additional debugging information to <code class="option">-d</code>.
73 Transaction signatures can be used to authenticate the Dynamic
74 DNS updates. These use the TSIG resource record type described
75 in RFC2845 or the SIG(0) record described in RFC3535 and
76 RFC2931 or GSS-TSIG as described in RFC3645. TSIG relies on
77 a shared secret that should only be known to
78 <span><strong class="command">nsupdate</strong></span> and the name server. Currently,
79 the only supported encryption algorithm for TSIG is HMAC-MD5,
80 which is defined in RFC 2104. Once other algorithms are
81 defined for TSIG, applications will need to ensure they select
82 the appropriate algorithm as well as the key when authenticating
83 each other. For instance, suitable <span class="type">key</span> and
84 <span class="type">server</span> statements would be added to
85 <code class="filename">/etc/named.conf</code> so that the name server
86 can associate the appropriate secret key and algorithm with
87 the IP address of the client application that will be using
88 TSIG authentication. SIG(0) uses public key cryptography.
89 To use a SIG(0) key, the public key must be stored in a KEY
90 record in a zone served by the name server.
91 <span><strong class="command">nsupdate</strong></span> does not read
92 <code class="filename">/etc/named.conf</code>.
93 GSS-TSIG uses Kerberos credentials.
95 <p><span><strong class="command">nsupdate</strong></span>
96 uses the <code class="option">-y</code> or <code class="option">-k</code> option
97 to provide the shared secret needed to generate a TSIG record
98 for authenticating Dynamic DNS update requests, default type
99 HMAC-MD5. These options are mutually exclusive. With the
100 <code class="option">-k</code> option, <span><strong class="command">nsupdate</strong></span> reads
101 the shared secret from the file <em class="parameter"><code>keyfile</code></em>,
102 whose name is of the form
103 <code class="filename">K{name}.+157.+{random}.private</code>. For
104 historical reasons, the file
105 <code class="filename">K{name}.+157.+{random}.key</code> must also be
106 present. When the <code class="option">-y</code> option is used, a
107 signature is generated from
108 [<span class="optional"><em class="parameter"><code>hmac:</code></em></span>]<em class="parameter"><code>keyname:secret.</code></em>
109 <em class="parameter"><code>keyname</code></em> is the name of the key, and
110 <em class="parameter"><code>secret</code></em> is the base64 encoded shared
111 secret. Use of the <code class="option">-y</code> option is discouraged
112 because the shared secret is supplied as a command line
113 argument in clear text. This may be visible in the output
115 <span class="citerefentry"><span class="refentrytitle">ps</span>(1)</span> or in a history file maintained by the user's
119 The <code class="option">-k</code> may also be used to specify a SIG(0) key used
120 to authenticate Dynamic DNS update requests. In this case, the key
121 specified is not an HMAC-MD5 key.
124 The <code class="option">-g</code> and <code class="option">-o</code> specify that
125 GSS-TSIG is to be used. The <code class="option">-o</code> should only
126 be used with old Microsoft Windows 2000 servers.
130 <span><strong class="command">nsupdate</strong></span>
131 uses UDP to send update requests to the name server unless they are too
132 large to fit in a UDP request in which case TCP will be used.
134 <code class="option">-v</code>
136 <span><strong class="command">nsupdate</strong></span>
137 use a TCP connection.
138 This may be preferable when a batch of update requests is made.
141 The <code class="option">-t</code> option sets the maximum time an update request
143 take before it is aborted. The default is 300 seconds. Zero can be
145 to disable the timeout.
148 The <code class="option">-u</code> option sets the UDP retry interval. The default
150 3 seconds. If zero, the interval will be computed from the timeout
152 and number of UDP retries.
155 The <code class="option">-r</code> option sets the number of UDP retries. The
157 3. If zero, only one update request will be made.
160 The <code class="option">-R <em class="replaceable"><code>randomdev</code></em></code> option
161 specifies a source of randomness. If the operating system
162 does not provide a <code class="filename">/dev/random</code> or
163 equivalent device, the default source of randomness is keyboard
164 input. <code class="filename">randomdev</code> specifies the name of
165 a character device or file containing random data to be used
166 instead of the default. The special value
167 <code class="filename">keyboard</code> indicates that keyboard input
168 should be used. This option may be specified multiple times.
171 <div class="refsect1" lang="en">
172 <a name="id2543726"></a><h2>INPUT FORMAT</h2>
173 <p><span><strong class="command">nsupdate</strong></span>
175 <em class="parameter"><code>filename</code></em>
177 Each command is supplied on exactly one line of input.
178 Some commands are for administrative purposes.
179 The others are either update instructions or prerequisite checks on the
180 contents of the zone.
181 These checks set conditions that some name or set of
182 resource records (RRset) either exists or is absent from the zone.
183 These conditions must be met if the entire update request is to succeed.
184 Updates will be rejected if the tests for the prerequisite conditions
188 Every update request consists of zero or more prerequisites
189 and zero or more updates.
190 This allows a suitably authenticated update request to proceed if some
191 specified resource records are present or missing from the zone.
192 A blank input line (or the <span><strong class="command">send</strong></span> command)
194 accumulated commands to be sent as one Dynamic DNS update request to the
198 The command formats and their meaning are as follows:
200 <div class="variablelist"><dl>
201 <dt><span class="term">
202 <span><strong class="command">server</strong></span>
207 Sends all dynamic update requests to the name server
208 <em class="parameter"><code>servername</code></em>.
209 When no server statement is provided,
210 <span><strong class="command">nsupdate</strong></span>
211 will send updates to the master server of the correct zone.
212 The MNAME field of that zone's SOA record will identify the
214 server for that zone.
215 <em class="parameter"><code>port</code></em>
216 is the port number on
217 <em class="parameter"><code>servername</code></em>
218 where the dynamic update requests get sent.
219 If no port number is specified, the default DNS port number of
223 <dt><span class="term">
224 <span><strong class="command">local</strong></span>
229 Sends all dynamic update requests using the local
230 <em class="parameter"><code>address</code></em>.
232 When no local statement is provided,
233 <span><strong class="command">nsupdate</strong></span>
234 will send updates using an address and port chosen by the
236 <em class="parameter"><code>port</code></em>
237 can additionally be used to make requests come from a specific
239 If no port number is specified, the system will assign one.
241 <dt><span class="term">
242 <span><strong class="command">zone</strong></span>
246 Specifies that all updates are to be made to the zone
247 <em class="parameter"><code>zonename</code></em>.
249 <em class="parameter"><code>zone</code></em>
250 statement is provided,
251 <span><strong class="command">nsupdate</strong></span>
252 will attempt determine the correct zone to update based on the
255 <dt><span class="term">
256 <span><strong class="command">class</strong></span>
260 Specify the default class.
261 If no <em class="parameter"><code>class</code></em> is specified, the
263 <em class="parameter"><code>IN</code></em>.
265 <dt><span class="term">
266 <span><strong class="command">ttl</strong></span>
270 Specify the default time to live for records to be added.
271 The value <em class="parameter"><code>none</code></em> will clear the default
274 <dt><span class="term">
275 <span><strong class="command">key</strong></span>
280 Specifies that all updates are to be TSIG-signed using the
281 <em class="parameter"><code>keyname</code></em> <em class="parameter"><code>keysecret</code></em> pair.
282 The <span><strong class="command">key</strong></span> command
283 overrides any key specified on the command line via
284 <code class="option">-y</code> or <code class="option">-k</code>.
286 <dt><span class="term">
287 <span><strong class="command">prereq nxdomain</strong></span>
291 Requires that no resource record of any type exists with name
292 <em class="parameter"><code>domain-name</code></em>.
294 <dt><span class="term">
295 <span><strong class="command">prereq yxdomain</strong></span>
300 <em class="parameter"><code>domain-name</code></em>
301 exists (has as at least one resource record, of any type).
303 <dt><span class="term">
304 <span><strong class="command">prereq nxrrset</strong></span>
310 Requires that no resource record exists of the specified
311 <em class="parameter"><code>type</code></em>,
312 <em class="parameter"><code>class</code></em>
314 <em class="parameter"><code>domain-name</code></em>.
316 <em class="parameter"><code>class</code></em>
317 is omitted, IN (internet) is assumed.
319 <dt><span class="term">
320 <span><strong class="command">prereq yxrrset</strong></span>
326 This requires that a resource record of the specified
327 <em class="parameter"><code>type</code></em>,
328 <em class="parameter"><code>class</code></em>
330 <em class="parameter"><code>domain-name</code></em>
333 <em class="parameter"><code>class</code></em>
334 is omitted, IN (internet) is assumed.
336 <dt><span class="term">
337 <span><strong class="command">prereq yxrrset</strong></span>
345 <em class="parameter"><code>data</code></em>
346 from each set of prerequisites of this form
348 <em class="parameter"><code>type</code></em>,
349 <em class="parameter"><code>class</code></em>,
351 <em class="parameter"><code>domain-name</code></em>
352 are combined to form a set of RRs. This set of RRs must
353 exactly match the set of RRs existing in the zone at the
355 <em class="parameter"><code>type</code></em>,
356 <em class="parameter"><code>class</code></em>,
358 <em class="parameter"><code>domain-name</code></em>.
360 <em class="parameter"><code>data</code></em>
361 are written in the standard text representation of the resource
365 <dt><span class="term">
366 <span><strong class="command">update delete</strong></span>
373 Deletes any resource records named
374 <em class="parameter"><code>domain-name</code></em>.
376 <em class="parameter"><code>type</code></em>
378 <em class="parameter"><code>data</code></em>
379 is provided, only matching resource records will be removed.
380 The internet class is assumed if
381 <em class="parameter"><code>class</code></em>
383 <em class="parameter"><code>ttl</code></em>
384 is ignored, and is only allowed for compatibility.
386 <dt><span class="term">
387 <span><strong class="command">update add</strong></span>
395 Adds a new resource record with the specified
396 <em class="parameter"><code>ttl</code></em>,
397 <em class="parameter"><code>class</code></em>
399 <em class="parameter"><code>data</code></em>.
401 <dt><span class="term">
402 <span><strong class="command">show</strong></span>
405 Displays the current message, containing all of the
407 updates specified since the last send.
409 <dt><span class="term">
410 <span><strong class="command">send</strong></span>
413 Sends the current message. This is equivalent to entering a
416 <dt><span class="term">
417 <span><strong class="command">answer</strong></span>
422 <dt><span class="term">
423 <span><strong class="command">debug</strong></span>
432 Lines beginning with a semicolon are comments and are ignored.
435 <div class="refsect1" lang="en">
436 <a name="id2544567"></a><h2>EXAMPLES</h2>
438 The examples below show how
439 <span><strong class="command">nsupdate</strong></span>
440 could be used to insert and delete resource records from the
441 <span class="type">example.com</span>
443 Notice that the input in each example contains a trailing blank line so
445 a group of commands are sent as one dynamic update request to the
446 master name server for
447 <span class="type">example.com</span>.
450 <pre class="programlisting">
452 > update delete oldhost.example.com A
453 > update add newhost.example.com 86400 A 172.16.1.1
460 <span class="type">oldhost.example.com</span>
463 <span class="type">newhost.example.com</span>
464 with IP address 172.16.1.1 is added.
465 The newly-added record has a 1 day TTL (86400 seconds).
467 <pre class="programlisting">
469 > prereq nxdomain nickname.example.com
470 > update add nickname.example.com 86400 CNAME somehost.example.com
476 The prerequisite condition gets the name server to check that there
477 are no resource records of any type for
478 <span class="type">nickname.example.com</span>.
480 If there are, the update request fails.
481 If this name does not exist, a CNAME for it is added.
482 This ensures that when the CNAME is added, it cannot conflict with the
483 long-standing rule in RFC1034 that a name must not exist as any other
484 record type if it exists as a CNAME.
485 (The rule has been updated for DNSSEC in RFC2535 to allow CNAMEs to have
486 RRSIG, DNSKEY and NSEC records.)
489 <div class="refsect1" lang="en">
490 <a name="id2544611"></a><h2>FILES</h2>
491 <div class="variablelist"><dl>
492 <dt><span class="term"><code class="constant">/etc/resolv.conf</code></span></dt>
494 used to identify default name server
496 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.key</code></span></dt>
498 base-64 encoding of HMAC-MD5 key created by
499 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
501 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.private</code></span></dt>
503 base-64 encoding of HMAC-MD5 key created by
504 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
508 <div class="refsect1" lang="en">
509 <a name="id2544680"></a><h2>SEE ALSO</h2>
510 <p><span class="citerefentry"><span class="refentrytitle">RFC2136</span></span>,
511 <span class="citerefentry"><span class="refentrytitle">RFC3007</span></span>,
512 <span class="citerefentry"><span class="refentrytitle">RFC2104</span></span>,
513 <span class="citerefentry"><span class="refentrytitle">RFC2845</span></span>,
514 <span class="citerefentry"><span class="refentrytitle">RFC1034</span></span>,
515 <span class="citerefentry"><span class="refentrytitle">RFC2535</span></span>,
516 <span class="citerefentry"><span class="refentrytitle">RFC2931</span></span>,
517 <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>,
518 <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
521 <div class="refsect1" lang="en">
522 <a name="id2542156"></a><h2>BUGS</h2>
524 The TSIG key is redundantly stored in two separate files.
525 This is a consequence of nsupdate using the DST library
526 for its cryptographic operations, and may change in future