contrib/bind9/bin/nsupdate/nsupdate.html

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  24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
  25 <a name="id2476275"></a><div class="titlepage"></div>
  26 <div class="refnamediv">
  27 <h2>Name</h2>
  28 <p>nsupdate &#8212; Dynamic DNS update utility</p>
  29 </div>
  30 <div class="refsynopsisdiv">
  31 <h2>Synopsis</h2>
  32 <div class="cmdsynopsis"><p><code class="command">nsupdate</code>  [<code class="option">-d</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">-v</code>] [filename]</p></div>
  33 </div>
  34 <div class="refsect1" lang="en">
  35 <a name="id2543417"></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
  38       to a name server.
  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
  42       one
  43       resource record.
  44     </p>
  45 <p>
  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.
  49       Manual edits could
  50       conflict with dynamic updates and cause data to be lost.
  51     </p>
  52 <p>
  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.
  58     </p>
  59 <p>
  60       The
  61       <code class="option">-d</code>
  62       option makes
  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.
  67     </p>
  68 <p>
  69       Transaction signatures can be used to authenticate the Dynamic DNS
  70       updates.
  71       These use the TSIG resource record type described in RFC2845 or the
  72       SIG(0) record described in RFC3535 and RFC2931.
  73       TSIG relies on a shared secret that should only be known to
  74       <span><strong class="command">nsupdate</strong></span> and the name server.
  75       Currently, the only supported encryption algorithm for TSIG is
  76       HMAC-MD5, which is defined in RFC 2104.
  77       Once other algorithms are defined for TSIG, applications will need to
  78       ensure they select the appropriate algorithm as well as the key when
  79       authenticating each other.
  80       For instance, suitable
  81       <span class="type">key</span>
  82       and
  83       <span class="type">server</span>
  84       statements would be added to
  85       <code class="filename">/etc/named.conf</code>
  86       so that the name server can associate the appropriate secret key
  87       and algorithm with the IP address of the
  88       client application that will be using TSIG authentication.
  89       SIG(0) uses public key cryptography.  To use a SIG(0) key, the public
  90       key must be stored in a KEY record in a zone served by the name server.
  91       <span><strong class="command">nsupdate</strong></span>
  92       does not read
  93       <code class="filename">/etc/named.conf</code>.
  94     </p>
  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
 114       from
 115       <span class="citerefentry"><span class="refentrytitle">ps</span>(1)</span> or in a history file maintained by the user's
 116       shell.
 117     </p>
 118 <p>
 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.
 122     </p>
 123 <p>
 124       By default
 125       <span><strong class="command">nsupdate</strong></span>
 126       uses UDP to send update requests to the name server unless they are too
 127       large to fit in a UDP request in which case TCP will be used.
 128       The
 129       <code class="option">-v</code>
 130       option makes
 131       <span><strong class="command">nsupdate</strong></span>
 132       use a TCP connection.
 133       This may be preferable when a batch of update requests is made.
 134     </p>
 135 <p>
 136       The <code class="option">-t</code> option sets the maximum time an update request
 137       can
 138       take before it is aborted.  The default is 300 seconds.  Zero can be
 139       used
 140       to disable the timeout.
 141     </p>
 142 <p>
 143       The <code class="option">-u</code> option sets the UDP retry interval.  The default
 144       is
 145       3 seconds.  If zero, the interval will be computed from the timeout
 146       interval
 147       and number of UDP retries.
 148     </p>
 149 <p>
 150       The <code class="option">-r</code> option sets the number of UDP retries. The
 151       default is
 152       3.  If zero, only one update request will be made.
 153     </p>
 154 </div>
 155 <div class="refsect1" lang="en">
 156 <a name="id2543645"></a><h2>INPUT FORMAT</h2>
 157 <p><span><strong class="command">nsupdate</strong></span>
 158       reads input from
 159       <em class="parameter"><code>filename</code></em>
 160       or standard input.
 161       Each command is supplied on exactly one line of input.
 162       Some commands are for administrative purposes.
 163       The others are either update instructions or prerequisite checks on the
 164       contents of the zone.
 165       These checks set conditions that some name or set of
 166       resource records (RRset) either exists or is absent from the zone.
 167       These conditions must be met if the entire update request is to succeed.
 168       Updates will be rejected if the tests for the prerequisite conditions
 169       fail.
 170     </p>
 171 <p>
 172       Every update request consists of zero or more prerequisites
 173       and zero or more updates.
 174       This allows a suitably authenticated update request to proceed if some
 175       specified resource records are present or missing from the zone.
 176       A blank input line (or the <span><strong class="command">send</strong></span> command)
 177       causes the
 178       accumulated commands to be sent as one Dynamic DNS update request to the
 179       name server.
 180     </p>
 181 <p>
 182       The command formats and their meaning are as follows:
 183       </p>
 184 <div class="variablelist"><dl>
 185 <dt><span class="term">
 186               <span><strong class="command">server</strong></span>
 187                {servername}
 188                [port]
 189             </span></dt>
 190 <dd><p>
 191               Sends all dynamic update requests to the name server
 192               <em class="parameter"><code>servername</code></em>.
 193               When no server statement is provided,
 194               <span><strong class="command">nsupdate</strong></span>
 195               will send updates to the master server of the correct zone.
 196               The MNAME field of that zone's SOA record will identify the
 197               master
 198               server for that zone.
 199               <em class="parameter"><code>port</code></em>
 200               is the port number on
 201               <em class="parameter"><code>servername</code></em>
 202               where the dynamic update requests get sent.
 203               If no port number is specified, the default DNS port number of
 204               53 is
 205               used.
 206             </p></dd>
 207 <dt><span class="term">
 208               <span><strong class="command">local</strong></span>
 209                {address}
 210                [port]
 211             </span></dt>
 212 <dd><p>
 213               Sends all dynamic update requests using the local
 214               <em class="parameter"><code>address</code></em>.
 215
 216               When no local statement is provided,
 217               <span><strong class="command">nsupdate</strong></span>
 218               will send updates using an address and port chosen by the
 219               system.
 220               <em class="parameter"><code>port</code></em>
 221               can additionally be used to make requests come from a specific
 222               port.
 223               If no port number is specified, the system will assign one.
 224             </p></dd>
 225 <dt><span class="term">
 226               <span><strong class="command">zone</strong></span>
 227                {zonename}
 228             </span></dt>
 229 <dd><p>
 230               Specifies that all updates are to be made to the zone
 231               <em class="parameter"><code>zonename</code></em>.
 232               If no
 233               <em class="parameter"><code>zone</code></em>
 234               statement is provided,
 235               <span><strong class="command">nsupdate</strong></span>
 236               will attempt determine the correct zone to update based on the
 237               rest of the input.
 238             </p></dd>
 239 <dt><span class="term">
 240               <span><strong class="command">class</strong></span>
 241                {classname}
 242             </span></dt>
 243 <dd><p>
 244               Specify the default class.
 245               If no <em class="parameter"><code>class</code></em> is specified, the
 246               default class is
 247               <em class="parameter"><code>IN</code></em>.
 248             </p></dd>
 249 <dt><span class="term">
 250               <span><strong class="command">key</strong></span>
 251                {name}
 252                {secret}
 253             </span></dt>
 254 <dd><p>
 255               Specifies that all updates are to be TSIG-signed using the
 256               <em class="parameter"><code>keyname</code></em> <em class="parameter"><code>keysecret</code></em> pair.
 257               The <span><strong class="command">key</strong></span> command
 258               overrides any key specified on the command line via
 259               <code class="option">-y</code> or <code class="option">-k</code>.
 260             </p></dd>
 261 <dt><span class="term">
 262               <span><strong class="command">prereq nxdomain</strong></span>
 263                {domain-name}
 264             </span></dt>
 265 <dd><p>
 266               Requires that no resource record of any type exists with name
 267               <em class="parameter"><code>domain-name</code></em>.
 268             </p></dd>
 269 <dt><span class="term">
 270               <span><strong class="command">prereq yxdomain</strong></span>
 271                {domain-name}
 272             </span></dt>
 273 <dd><p>
 274               Requires that
 275               <em class="parameter"><code>domain-name</code></em>
 276               exists (has as at least one resource record, of any type).
 277             </p></dd>
 278 <dt><span class="term">
 279               <span><strong class="command">prereq nxrrset</strong></span>
 280                {domain-name}
 281                [class]
 282                {type}
 283             </span></dt>
 284 <dd><p>
 285               Requires that no resource record exists of the specified
 286               <em class="parameter"><code>type</code></em>,
 287               <em class="parameter"><code>class</code></em>
 288               and
 289               <em class="parameter"><code>domain-name</code></em>.
 290               If
 291               <em class="parameter"><code>class</code></em>
 292               is omitted, IN (internet) is assumed.
 293             </p></dd>
 294 <dt><span class="term">
 295               <span><strong class="command">prereq yxrrset</strong></span>
 296                {domain-name}
 297                [class]
 298                {type}
 299             </span></dt>
 300 <dd><p>
 301               This requires that a resource record of the specified
 302               <em class="parameter"><code>type</code></em>,
 303               <em class="parameter"><code>class</code></em>
 304               and
 305               <em class="parameter"><code>domain-name</code></em>
 306               must exist.
 307               If
 308               <em class="parameter"><code>class</code></em>
 309               is omitted, IN (internet) is assumed.
 310             </p></dd>
 311 <dt><span class="term">
 312               <span><strong class="command">prereq yxrrset</strong></span>
 313                {domain-name}
 314                [class]
 315                {type}
 316                {data...}
 317             </span></dt>
 318 <dd><p>
 319               The
 320               <em class="parameter"><code>data</code></em>
 321               from each set of prerequisites of this form
 322               sharing a common
 323               <em class="parameter"><code>type</code></em>,
 324               <em class="parameter"><code>class</code></em>,
 325               and
 326               <em class="parameter"><code>domain-name</code></em>
 327               are combined to form a set of RRs.  This set of RRs must
 328               exactly match the set of RRs existing in the zone at the
 329               given
 330               <em class="parameter"><code>type</code></em>,
 331               <em class="parameter"><code>class</code></em>,
 332               and
 333               <em class="parameter"><code>domain-name</code></em>.
 334               The
 335               <em class="parameter"><code>data</code></em>
 336               are written in the standard text representation of the resource
 337               record's
 338               RDATA.
 339             </p></dd>
 340 <dt><span class="term">
 341               <span><strong class="command">update delete</strong></span>
 342                {domain-name}
 343                [ttl]
 344                [class]
 345                [type [data...]]
 346             </span></dt>
 347 <dd><p>
 348               Deletes any resource records named
 349               <em class="parameter"><code>domain-name</code></em>.
 350               If
 351               <em class="parameter"><code>type</code></em>
 352               and
 353               <em class="parameter"><code>data</code></em>
 354               is provided, only matching resource records will be removed.
 355               The internet class is assumed if
 356               <em class="parameter"><code>class</code></em>
 357               is not supplied.  The
 358               <em class="parameter"><code>ttl</code></em>
 359               is ignored, and is only allowed for compatibility.
 360             </p></dd>
 361 <dt><span class="term">
 362               <span><strong class="command">update add</strong></span>
 363                {domain-name}
 364                {ttl}
 365                [class]
 366                {type}
 367                {data...}
 368             </span></dt>
 369 <dd><p>
 370               Adds a new resource record with the specified
 371               <em class="parameter"><code>ttl</code></em>,
 372               <em class="parameter"><code>class</code></em>
 373               and
 374               <em class="parameter"><code>data</code></em>.
 375             </p></dd>
 376 <dt><span class="term">
 377               <span><strong class="command">show</strong></span>
 378             </span></dt>
 379 <dd><p>
 380               Displays the current message, containing all of the
 381               prerequisites and
 382               updates specified since the last send.
 383             </p></dd>
 384 <dt><span class="term">
 385               <span><strong class="command">send</strong></span>
 386             </span></dt>
 387 <dd><p>
 388               Sends the current message.  This is equivalent to entering a
 389               blank line.
 390             </p></dd>
 391 <dt><span class="term">
 392               <span><strong class="command">answer</strong></span>
 393             </span></dt>
 394 <dd><p>
 395               Displays the answer.
 396             </p></dd>
 397 </dl></div>
 398 <p>
 399     </p>
 400 <p>
 401       Lines beginning with a semicolon are comments and are ignored.
 402     </p>
 403 </div>
 404 <div class="refsect1" lang="en">
 405 <a name="id2544648"></a><h2>EXAMPLES</h2>
 406 <p>
 407       The examples below show how
 408       <span><strong class="command">nsupdate</strong></span>
 409       could be used to insert and delete resource records from the
 410       <span class="type">example.com</span>
 411       zone.
 412       Notice that the input in each example contains a trailing blank line so
 413       that
 414       a group of commands are sent as one dynamic update request to the
 415       master name server for
 416       <span class="type">example.com</span>.
 417
 418       </p>
 419 <pre class="programlisting">
 420 # nsupdate
 421 &gt; update delete oldhost.example.com A
 422 &gt; update add newhost.example.com 86400 A 172.16.1.1
 423 &gt; send
 424 </pre>
 425 <p>
 426     </p>
 427 <p>
 428       Any A records for
 429       <span class="type">oldhost.example.com</span>
 430       are deleted.
 431       And an A record for
 432       <span class="type">newhost.example.com</span>
 433       with IP address 172.16.1.1 is added.
 434       The newly-added record has a 1 day TTL (86400 seconds).
 435       </p>
 436 <pre class="programlisting">
 437 # nsupdate
 438 &gt; prereq nxdomain nickname.example.com
 439 &gt; update add nickname.example.com 86400 CNAME somehost.example.com
 440 &gt; send
 441 </pre>
 442 <p>
 443     </p>
 444 <p>
 445       The prerequisite condition gets the name server to check that there
 446       are no resource records of any type for
 447       <span class="type">nickname.example.com</span>.
 448
 449       If there are, the update request fails.
 450       If this name does not exist, a CNAME for it is added.
 451       This ensures that when the CNAME is added, it cannot conflict with the
 452       long-standing rule in RFC1034 that a name must not exist as any other
 453       record type if it exists as a CNAME.
 454       (The rule has been updated for DNSSEC in RFC2535 to allow CNAMEs to have
 455       RRSIG, DNSKEY and NSEC records.)
 456     </p>
 457 </div>
 458 <div class="refsect1" lang="en">
 459 <a name="id2544692"></a><h2>FILES</h2>
 460 <div class="variablelist"><dl>
 461 <dt><span class="term"><code class="constant">/etc/resolv.conf</code></span></dt>
 462 <dd><p>
 463             used to identify default name server
 464           </p></dd>
 465 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.key</code></span></dt>
 466 <dd><p>
 467             base-64 encoding of HMAC-MD5 key created by
 468             <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
 469           </p></dd>
 470 <dt><span class="term"><code class="constant">K{name}.+157.+{random}.private</code></span></dt>
 471 <dd><p>
 472             base-64 encoding of HMAC-MD5 key created by
 473             <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
 474           </p></dd>
 475 </dl></div>
 476 </div>
 477 <div class="refsect1" lang="en">
 478 <a name="id2544829"></a><h2>SEE ALSO</h2>
 479 <p><span class="citerefentry"><span class="refentrytitle">RFC2136</span></span>,
 480       <span class="citerefentry"><span class="refentrytitle">RFC3007</span></span>,
 481       <span class="citerefentry"><span class="refentrytitle">RFC2104</span></span>,
 482       <span class="citerefentry"><span class="refentrytitle">RFC2845</span></span>,
 483       <span class="citerefentry"><span class="refentrytitle">RFC1034</span></span>,
 484       <span class="citerefentry"><span class="refentrytitle">RFC2535</span></span>,
 485       <span class="citerefentry"><span class="refentrytitle">RFC2931</span></span>,
 486       <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>,
 487       <span class="citerefentry"><span class="refentrytitle">dnssec-keygen</span>(8)</span>.
 488     </p>
 489 </div>
 490 <div class="refsect1" lang="en">
 491 <a name="id2544900"></a><h2>BUGS</h2>
 492 <p>
 493       The TSIG key is redundantly stored in two separate files.
 494       This is a consequence of nsupdate using the DST library
 495       for its cryptographic operations, and may change in future
 496       releases.
 497     </p>
 498 </div>
 499 </div></body>
 500 </html>