1NSUPDATE(1) BIND 9 NSUPDATE(1)
2
6 nsupdate - dynamic DNS update utility
7
9 nsupdate [-d] [-D] [-i] [-L level] [ [-g] | [-o] | [-l] | [-y
10 [hmac:]keyname:secret] | [-k keyfile] ] [ [-S] [-K tlskeyfile] [-E
11 tlscertfile] [-A tlscafile] [-H tlshostname] [-O] ] [-t timeout] [-u
12 udptimeout] [-r udpretries] [-v] [-T] [-P] [-V] [ [-4] | [-6] ] [file‐
13 name]
14
16 nsupdate is used to submit Dynamic DNS Update requests, as defined in
17 RFC 2136, to a name server. This allows resource records to be added or
18 removed from a zone without manually editing the zone file. A single
19 update request can contain requests to add or remove more than one re‐
20 source record.
21 Zones that are under dynamic control via nsupdate or a DHCP server
23 should not be edited by hand. Manual edits could conflict with dynamic
24 updates and cause data to be lost.
25 The resource records that are dynamically added or removed with nsup‐
27 date must be in the same zone. Requests are sent to the zone's primary
28 server, which is identified by the MNAME field of the zone's SOA
29 record.
30 Transaction signatures can be used to authenticate the Dynamic DNS up‐
32 dates. These use the TSIG resource record type described in RFC 2845,
33 the SIG(0) record described in RFC 2535 and RFC 2931, or GSS-TSIG as
34 described in RFC 3645.
35 TSIG relies on a shared secret that should only be known to nsupdate
37 and the name server. For instance, suitable key and server statements
38 are added to /etc/named.conf so that the name server can associate the
39 appropriate secret key and algorithm with the IP address of the client
40 application that is using TSIG authentication. ddns-confgen can gener‐
41 ate suitable configuration fragments. nsupdate uses the -y or -k op‐
42 tions to provide the TSIG shared secret; these options are mutually ex‐
43 clusive.
44 SIG(0) uses public key cryptography. To use a SIG(0) key, the public
46 key must be stored in a KEY record in a zone served by the name server.
47 GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode is switched
49 on with the -g flag. A non-standards-compliant variant of GSS-TSIG used
50 by Windows 2000 can be switched on with the -o flag.
51
53 -4 This option sets use of IPv4 only.
54 -6 This option sets use of IPv6 only.
56 -A tlscafile
58 This option specifies the file of the certificate authorities
59 (CA) certificates (in PEM format) in order to verify the remote
60 server TLS certificate when using DNS-over-TLS (DoT), to achieve
61 Strict or Mutual TLS. When used, it will override the certifi‐
62 cates from the global certificates store, which are otherwise
63 used by default when -S is enabled. This option can not be used
64 in conjuction with -O, and it implies -S.
65 -C Overrides the default resolv.conf file. This is only intended
67 for testing.
68 -d This option sets debug mode, which provides tracing information
70 about the update requests that are made and the replies received
71 from the name server.
72 -D This option sets extra debug mode.
74 -E tlscertfile
76 This option sets the certificate(s) file for authentication for
77 the DNS-over-TLS (DoT) transport to the remote server. The cer‐
78 tificate chain file is expected to be in PEM format. This option
79 implies -S, and can only be used with -K.
80 -g This option enables standard GSS-TSIG mode.
82 -H tlshostname
84 This option makes nsupdate use the provided hostname during re‐
85 mote server TLS certificate verification. Otherwise, the DNS
86 server name is used. This option implies -S.
87 -i This option forces interactive mode, even when standard input is
89 not a terminal.
90 -k keyfile
92 This option indicates the file containing the TSIG authentica‐
93 tion key. Keyfiles may be in two formats: a single file contain‐
94 ing a named.conf-format key statement, which may be generated
95 automatically by ddns-confgen; or a pair of files whose names
96 are of the format K{name}.+157.+{random}.key and
97 K{name}.+157.+{random}.private, which can be generated by
98 dnssec-keygen. The -k option can also be used to specify a
99 SIG(0) key used to authenticate Dynamic DNS update requests. In
100 this case, the key specified is not an HMAC-MD5 key.
101 -K tlskeyfile
103 This option sets the key file for authenticated encryption for
104 the DNS-over-TLS (DoT) transport with the remote server. The
105 private key file is expected to be in PEM format. This option
106 implies -S, and can only be used with -E.
107 -l This option sets local-host only mode, which sets the server ad‐
109 dress to localhost (disabling the server so that the server ad‐
110 dress cannot be overridden). Connections to the local server use
111 a TSIG key found in /run/session.key, which is automatically
112 generated by named if any local primary zone has set update-pol‐
113 icy to local. The location of this key file can be overridden
114 with the -k option.
115 -L level
117 This option sets the logging debug level. If zero, logging is
118 disabled.
119 -o This option is deprecated. Previously, it enabled a non-stan‐
121 dards-compliant variant of GSS-TSIG that was used by Windows
122 2000. Since that OS is now long past its end of life, this op‐
123 tion is now treated as a synonym for -g.
124 -O This option enables Opportunistic TLS. When used, the remote
126 peer's TLS certificate will not be verified. This option should
127 be used for debugging purposes only, and it is not recommended
128 to use it in production. This option can not be used in conjuc‐
129 tion with -A, and it implies -S.
130 -p port
132 This option sets the port to use for connections to a name
133 server. The default is 53.
134 -P This option prints the list of private BIND-specific resource
136 record types whose format is understood by nsupdate. See also
137 the -T option.
138 -r udpretries
140 This option sets the number of UDP retries. The default is 3. If
141 zero, only one update request is made.
142 -S This option indicates whether to use DNS-over-TLS (DoT) when
144 querying name servers specified by server servername port syntax
145 in the input file, and the primary server discovered through a
146 SOA request. When the -K and -E options are used, then the spec‐
147 ified TLS client certificate and private key pair are used for
148 authentication (Mutual TLS). This option implies -v.
149 -t timeout
151 This option sets the maximum time an update request can take be‐
152 fore it is aborted. The default is 300 seconds. If zero, the
153 timeout is disabled for TCP mode. For UDP mode, the option -u
154 takes precedence over this option, unless the option -u is set
155 to zero, in which case the interval is computed from the -t
156 timeout interval and the number of UDP retries. For UDP mode,
157 the timeout can not be disabled, and will be rounded up to 1
158 second in case if both -t and -u are set to zero.
159 -T This option prints the list of IANA standard resource record
161 types whose format is understood by nsupdate. nsupdate exits af‐
162 ter the lists are printed. The -T option can be combined with
163 the -P option.
164 Other types can be entered using TYPEXXXXX where XXXXX is the
166 decimal value of the type with no leading zeros. The rdata, if
167 present, is parsed using the UNKNOWN rdata format, (<backslash>
168 <hash> <space> <length> <space> <hexstring>).
169 -u udptimeout
171 This option sets the UDP retry interval. The default is 3 sec‐
172 onds. If zero, the interval is computed from the timeout inter‐
173 val and number of UDP retries.
174 -v This option specifies that TCP should be used even for small up‐
176 date requests. By default, nsupdate uses UDP to send update re‐
177 quests to the name server unless they are too large to fit in a
178 UDP request, in which case TCP is used. TCP may be preferable
179 when a batch of update requests is made.
180 -V This option prints the version number and exits.
182 -y [hmac:]keyname:secret
184 This option sets the literal TSIG authentication key. keyname is
185 the name of the key, and secret is the base64 encoded shared se‐
186 cret. hmac is the name of the key algorithm; valid choices are
187 hmac-md5, hmac-sha1, hmac-sha224, hmac-sha256, hmac-sha384, or
188 hmac-sha512. If hmac is not specified, the default is hmac-md5,
189 or if MD5 was disabled, hmac-sha256.
190 NOTE: Use of the -y option is discouraged because the shared se‐
192 cret is supplied as a command-line argument in clear text. This
193 may be visible in the output from ps1 or in a history file main‐
194 tained by the user's shell.
195
197 nsupdate reads input from filename or standard input. Each command is
198 supplied on exactly one line of input. Some commands are for adminis‐
199 trative purposes; others are either update instructions or prerequisite
200 checks on the contents of the zone. These checks set conditions that
201 some name or set of resource records (RRset) either exists or is absent
202 from the zone. These conditions must be met if the entire update re‐
203 quest is to succeed. Updates are rejected if the tests for the prereq‐
204 uisite conditions fail.
205 Every update request consists of zero or more prerequisites and zero or
207 more updates. This allows a suitably authenticated update request to
208 proceed if some specified resource records are either present or miss‐
209 ing from the zone. A blank input line (or the send command) causes the
210 accumulated commands to be sent as one Dynamic DNS update request to
211 the name server.
212 The command formats and their meanings are as follows:
214 server servername port
216 This command sends all dynamic update requests to the name
217 server servername. When no server statement is provided, nsup‐
218 date sends updates to the primary server of the correct zone.
219 The MNAME field of that zone's SOA record identify the primary
220 server for that zone. port is the port number on servername
221 where the dynamic update requests are sent. If no port number is
222 specified, the default DNS port number of 53 is used.
223 NOTE:
225 This command has no effect when GSS-TSIG is in use.
226 local address port
228 This command sends all dynamic update requests using the local
229 address. When no local statement is provided, nsupdate sends up‐
230 dates using an address and port chosen by the system. port can
231 also be used to force requests to come from a specific port. If
232 no port number is specified, the system assigns one.
233 zone zonename
235 This command specifies that all updates are to be made to the
236 zone zonename. If no zone statement is provided, nsupdate at‐
237 tempts to determine the correct zone to update based on the rest
238 of the input.
239 class classname
241 This command specifies the default class. If no class is speci‐
242 fied, the default class is IN.
243 ttl seconds
245 This command specifies the default time-to-live, in seconds, for
246 records to be added. The value none clears the default TTL.
247 key hmac:keyname secret
249 This command specifies that all updates are to be TSIG-signed
250 using the keyname-secret pair. If hmac is specified, it sets the
251 signing algorithm in use. The default is hmac-md5; if MD5 was
252 disabled, the default is hmac-sha256. The key command overrides
253 any key specified on the command line via -y or -k.
254 gsstsig
256 This command uses GSS-TSIG to sign the updates. This is equiva‐
257 lent to specifying -g on the command line.
258 oldgsstsig
260 This command is deprecated and will be removed in a future re‐
261 lease. Previously, it caused nsupdate to use the Windows 2000
262 version of GSS-TSIG to sign updates. It is now treated as a syn‐
263 onym for gsstsig.
264 realm [realm_name]
266 When using GSS-TSIG, this command specifies the use of
267 realm_name rather than the default realm in krb5.conf. If no
268 realm is specified, the saved realm is cleared.
269 check-names [boolean]
271 This command turns on or off check-names processing on records
272 to be added. Check-names has no effect on prerequisites or
273 records to be deleted. By default check-names processing is on.
274 If check-names processing fails, the record is not added to the
275 UPDATE message.
276 check-svbc [boolean]
278 This command turns on or off check-svcb processing on records to
279 be added. Check-svcb has no effect on prerequisites or records
280 to be deleted. By default check-svcb processing is on. If
281 check-svcb processing fails, the record is not added to the UP‐
282 DATE message.
283 prereq nxdomain domain-name
285 This command requires that no resource record of any type exist
286 with the name domain-name.
287 prereq yxdomain domain-name
289 This command requires that domain-name exist (as at least one
290 resource record, of any type).
291 prereq nxrrset domain-name class type
293 This command requires that no resource record exist of the spec‐
294 ified type, class, and domain-name. If class is omitted, IN (In‐
295 ternet) is assumed.
296 prereq yxrrset domain-name class type
298 This command requires that a resource record of the specified
299 type, class and domain-name exist. If class is omitted, IN (in‐
300 ternet) is assumed.
301 prereq yxrrset domain-name class type data
303 With this command, the data from each set of prerequisites of
304 this form sharing a common type, class, and domain-name are com‐
305 bined to form a set of RRs. This set of RRs must exactly match
306 the set of RRs existing in the zone at the given type, class,
307 and domain-name. The data are written in the standard text rep‐
308 resentation of the resource record's RDATA.
309 update delete domain-name ttl class type data
311 This command deletes any resource records named domain-name. If
312 type and data are provided, only matching resource records are
313 removed. The Internet class is assumed if class is not sup‐
314 plied. The ttl is ignored, and is only allowed for compatibil‐
315 ity.
316 update add domain-name ttl class type data
318 This command adds a new resource record with the specified ttl,
319 class, and data.
320 show This command displays the current message, containing all of the
322 prerequisites and updates specified since the last send.
323 send This command sends the current message. This is equivalent to
325 entering a blank line.
326 answer This command displays the answer.
328 debug This command turns on debugging.
330 version
332 This command prints the version number.
333 help This command prints a list of commands.
335 Lines beginning with a semicolon (;) are comments and are ignored.
337
339 The examples below show how nsupdate can be used to insert and delete
340 resource records from the example.com zone. Notice that the input in
341 each example contains a trailing blank line, so that a group of com‐
342 mands is sent as one dynamic update request to the primary name server
343 for example.com.
344 # nsupdate
346 > update delete oldhost.example.com A
347 > update add newhost.example.com 86400 A 172.16.1.1
348 > send
349 Any A records for oldhost.example.com are deleted, and an A record for
351 newhost.example.com with IP address 172.16.1.1 is added. The newly
352 added record has a TTL of 1 day (86400 seconds).
353 # nsupdate
355 > prereq nxdomain nickname.example.com
356 > update add nickname.example.com 86400 CNAME somehost.example.com
357 > send
358 The prerequisite condition tells the name server to verify that there
360 are no resource records of any type for nickname.example.com. If there
361 are, the update request fails. If this name does not exist, a CNAME for
362 it is added. This ensures that when the CNAME is added, it cannot con‐
363 flict with the long-standing rule in RFC 1034 that a name must not ex‐
364 ist as any other record type if it exists as a CNAME. (The rule has
365 been updated for DNSSEC in RFC 2535 to allow CNAMEs to have RRSIG,
366 DNSKEY, and NSEC records.)
367
369 /etc/resolv.conf
370 Used to identify the default name server
371 /run/session.key
373 Sets the default TSIG key for use in local-only mode
374 K{name}.+157.+{random}.key
376 Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
377 K{name}.+157.+{random}.private
379 Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
380
382 RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931,
383 named(8), dnssec-keygen(8), tsig-keygen(8).
384
386 The TSIG key is redundantly stored in two separate files. This is a
387 consequence of nsupdate using the DST library for its cryptographic op‐
388 erations, and may change in future releases.
389
391 Internet Systems Consortium
392
394 2023, Internet Systems Consortium
3959.19.18 NSUPDATE(1)