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] ] [-t timeout] [-u udptimeout]
11 [-r udpretries] [-v] [-T] [-P] [-V] [ [-4] | [-6] ] [filename]
12
14 nsupdate is used to submit Dynamic DNS Update requests, as defined in
15 RFC 2136, to a name server. This allows resource records to be added or
16 removed from a zone without manually editing the zone file. A single
17 update request can contain requests to add or remove more than one re‐
18 source record.
19 Zones that are under dynamic control via nsupdate or a DHCP server
21 should not be edited by hand. Manual edits could conflict with dynamic
22 updates and cause data to be lost.
23 The resource records that are dynamically added or removed with nsup‐
25 date must be in the same zone. Requests are sent to the zone's primary
26 server, which is identified by the MNAME field of the zone's SOA
27 record.
28 Transaction signatures can be used to authenticate the Dynamic DNS up‐
30 dates. These use the TSIG resource record type described in RFC 2845,
31 the SIG(0) record described in RFC 2535 and RFC 2931, or GSS-TSIG as
32 described in RFC 3645.
33 TSIG relies on a shared secret that should only be known to nsupdate
35 and the name server. For instance, suitable key and server statements
36 are added to /etc/named.conf so that the name server can associate the
37 appropriate secret key and algorithm with the IP address of the client
38 application that is using TSIG authentication. ddns-confgen can gener‐
39 ate suitable configuration fragments. nsupdate uses the -y or -k op‐
40 tions to provide the TSIG shared secret; these options are mutually ex‐
41 clusive.
42 SIG(0) uses public key cryptography. To use a SIG(0) key, the public
44 key must be stored in a KEY record in a zone served by the name server.
45 GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode is switched
47 on with the -g flag. A non-standards-compliant variant of GSS-TSIG used
48 by Windows 2000 can be switched on with the -o flag.
49
51 -4 This option sets use of IPv4 only.
52 -6 This option sets use of IPv6 only.
54 -C Overrides the default resolv.conf file. This is only intended
56 for testing.
57 -d This option sets debug mode, which provides tracing information
59 about the update requests that are made and the replies received
60 from the name server.
61 -D This option sets extra debug mode.
63 -g This option enables standard GSS-TSIG mode.
65 -i This option forces interactive mode, even when standard input is
67 not a terminal.
68 -k keyfile
70 This option indicates the file containing the TSIG authentica‐
71 tion key. Keyfiles may be in two formats: a single file contain‐
72 ing a named.conf-format key statement, which may be generated
73 automatically by ddns-confgen; or a pair of files whose names
74 are of the format K{name}.+157.+{random}.key and
75 K{name}.+157.+{random}.private, which can be generated by
76 dnssec-keygen. The -k option can also be used to specify a
77 SIG(0) key used to authenticate Dynamic DNS update requests. In
78 this case, the key specified is not an HMAC-MD5 key.
79 -l This option sets local-host only mode, which sets the server ad‐
81 dress to localhost (disabling the server so that the server ad‐
82 dress cannot be overridden). Connections to the local server use
83 a TSIG key found in /var/run/session.key, which is automatically
84 generated by named if any local primary zone has set update-pol‐
85 icy to local. The location of this key file can be overridden
86 with the -k option.
87 -L level
89 This option sets the logging debug level. If zero, logging is
90 disabled.
91 -o This option enables a non-standards-compliant variant of
93 GSS-TSIG used by Windows 2000.
94 -p port
96 This option sets the port to use for connections to a name
97 server. The default is 53.
98 -P This option prints the list of private BIND-specific resource
100 record types whose format is understood by nsupdate. See also
101 the -T option.
102 -r udpretries
104 This option sets the number of UDP retries. The default is 3. If
105 zero, only one update request is made.
106 -t timeout
108 This option sets the maximum time an update request can take be‐
109 fore it is aborted. The default is 300 seconds. If zero, the
110 timeout is disabled.
111 -T This option prints the list of IANA standard resource record
113 types whose format is understood by nsupdate. nsupdate exits af‐
114 ter the lists are printed. The -T option can be combined with
115 the -P option.
116 Other types can be entered using TYPEXXXXX where XXXXX is the
118 decimal value of the type with no leading zeros. The rdata, if
119 present, is parsed using the UNKNOWN rdata format, (<backslash>
120 <hash> <space> <length> <space> <hexstring>).
121 -u udptimeout
123 This option sets the UDP retry interval. The default is 3 sec‐
124 onds. If zero, the interval is computed from the timeout inter‐
125 val and number of UDP retries.
126 -v This option specifies that TCP should be used even for small up‐
128 date requests. By default, nsupdate uses UDP to send update re‐
129 quests to the name server unless they are too large to fit in a
130 UDP request, in which case TCP is used. TCP may be preferable
131 when a batch of update requests is made.
132 -V This option prints the version number and exits.
134 -y [hmac:]keyname:secret
136 This option sets the literal TSIG authentication key. keyname is
137 the name of the key, and secret is the base64 encoded shared se‐
138 cret. hmac is the name of the key algorithm; valid choices are
139 hmac-md5, hmac-sha1, hmac-sha224, hmac-sha256, hmac-sha384, or
140 hmac-sha512. If hmac is not specified, the default is hmac-md5,
141 or if MD5 was disabled, hmac-sha256.
142 NOTE: Use of the -y option is discouraged because the shared se‐
144 cret is supplied as a command-line argument in clear text. This
145 may be visible in the output from ps1 or in a history file main‐
146 tained by the user's shell.
147
149 nsupdate reads input from filename or standard input. Each command is
150 supplied on exactly one line of input. Some commands are for adminis‐
151 trative purposes; others are either update instructions or prerequisite
152 checks on the contents of the zone. These checks set conditions that
153 some name or set of resource records (RRset) either exists or is absent
154 from the zone. These conditions must be met if the entire update re‐
155 quest is to succeed. Updates are rejected if the tests for the prereq‐
156 uisite conditions fail.
157 Every update request consists of zero or more prerequisites and zero or
159 more updates. This allows a suitably authenticated update request to
160 proceed if some specified resource records are either present or miss‐
161 ing from the zone. A blank input line (or the send command) causes the
162 accumulated commands to be sent as one Dynamic DNS update request to
163 the name server.
164 The command formats and their meanings are as follows:
166 server servername port
168 This command sends all dynamic update requests to the name
169 server servername. When no server statement is provided, nsup‐
170 date sends updates to the primary server of the correct zone.
171 The MNAME field of that zone's SOA record identify the primary
172 server for that zone. port is the port number on servername
173 where the dynamic update requests are sent. If no port number is
174 specified, the default DNS port number of 53 is used.
175 NOTE:
177 This command has no effect when GSS-TSIG is in use.
178 local address port
180 This command sends all dynamic update requests using the local
181 address. When no local statement is provided, nsupdate sends up‐
182 dates using an address and port chosen by the system. port can
183 also be used to force requests to come from a specific port. If
184 no port number is specified, the system assigns one.
185 zone zonename
187 This command specifies that all updates are to be made to the
188 zone zonename. If no zone statement is provided, nsupdate at‐
189 tempts to determine the correct zone to update based on the rest
190 of the input.
191 class classname
193 This command specifies the default class. If no class is speci‐
194 fied, the default class is IN.
195 ttl seconds
197 This command specifies the default time-to-live, in seconds, for
198 records to be added. The value none clears the default TTL.
199 key hmac:keyname secret
201 This command specifies that all updates are to be TSIG-signed
202 using the keyname-secret pair. If hmac is specified, it sets the
203 signing algorithm in use. The default is hmac-md5; if MD5 was
204 disabled, the default is hmac-sha256. The key command overrides
205 any key specified on the command line via -y or -k.
206 gsstsig
208 This command uses GSS-TSIG to sign the updates. This is equiva‐
209 lent to specifying -g on the command line.
210 oldgsstsig
212 This command uses the Windows 2000 version of GSS-TSIG to sign
213 the updates. This is equivalent to specifying -o on the command
214 line.
215 realm [realm_name]
217 When using GSS-TSIG, this command specifies the use of
218 realm_name rather than the default realm in krb5.conf. If no
219 realm is specified, the saved realm is cleared.
220 check-names [boolean]
222 This command turns on or off check-names processing on records
223 to be added. Check-names has no effect on prerequisites or
224 records to be deleted. By default check-names processing is on.
225 If check-names processing fails, the record is not added to the
226 UPDATE message.
227 prereq nxdomain domain-name
229 This command requires that no resource record of any type exist
230 with the name domain-name.
231 prereq yxdomain domain-name
233 This command requires that domain-name exist (as at least one
234 resource record, of any type).
235 prereq nxrrset domain-name class type
237 This command requires that no resource record exist of the spec‐
238 ified type, class, and domain-name. If class is omitted, IN (In‐
239 ternet) is assumed.
240 prereq yxrrset domain-name class type
242 This command requires that a resource record of the specified
243 type, class and domain-name exist. If class is omitted, IN (in‐
244 ternet) is assumed.
245 prereq yxrrset domain-name class type data
247 With this command, the data from each set of prerequisites of
248 this form sharing a common type, class, and domain-name are com‐
249 bined to form a set of RRs. This set of RRs must exactly match
250 the set of RRs existing in the zone at the given type, class,
251 and domain-name. The data are written in the standard text rep‐
252 resentation of the resource record's RDATA.
253 update delete domain-name ttl class type data
255 This command deletes any resource records named domain-name. If
256 type and data are provided, only matching resource records are
257 removed. The Internet class is assumed if class is not sup‐
258 plied. The ttl is ignored, and is only allowed for compatibil‐
259 ity.
260 update add domain-name ttl class type data
262 This command adds a new resource record with the specified ttl,
263 class, and data.
264 show This command displays the current message, containing all of the
266 prerequisites and updates specified since the last send.
267 send This command sends the current message. This is equivalent to
269 entering a blank line.
270 answer This command displays the answer.
272 debug This command turns on debugging.
274 version
276 This command prints the version number.
277 help This command prints a list of commands.
279 Lines beginning with a semicolon (;) are comments and are ignored.
281
283 The examples below show how nsupdate can be used to insert and delete
284 resource records from the example.com zone. Notice that the input in
285 each example contains a trailing blank line, so that a group of com‐
286 mands is sent as one dynamic update request to the primary name server
287 for example.com.
288 # nsupdate
290 > update delete oldhost.example.com A
291 > update add newhost.example.com 86400 A 172.16.1.1
292 > send
293 Any A records for oldhost.example.com are deleted, and an A record for
295 newhost.example.com with IP address 172.16.1.1 is added. The newly
296 added record has a TTL of 1 day (86400 seconds).
297 # nsupdate
299 > prereq nxdomain nickname.example.com
300 > update add nickname.example.com 86400 CNAME somehost.example.com
301 > send
302 The prerequisite condition tells the name server to verify that there
304 are no resource records of any type for nickname.example.com. If there
305 are, the update request fails. If this name does not exist, a CNAME for
306 it is added. This ensures that when the CNAME is added, it cannot con‐
307 flict with the long-standing rule in RFC 1034 that a name must not ex‐
308 ist as any other record type if it exists as a CNAME. (The rule has
309 been updated for DNSSEC in RFC 2535 to allow CNAMEs to have RRSIG,
310 DNSKEY, and NSEC records.)
311
313 /etc/resolv.conf
314 Used to identify the default name server
315 /var/run/session.key
317 Sets the default TSIG key for use in local-only mode
318 K{name}.+157.+{random}.key
320 Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
321 K{name}.+157.+{random}.private
323 Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
324
326 RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931,
327 named(8), dnssec-keygen(8), tsig-keygen(8).
328
330 The TSIG key is redundantly stored in two separate files. This is a
331 consequence of nsupdate using the DST library for its cryptographic op‐
332 erations, and may change in future releases.
333
335 Internet Systems Consortium
336
338 2023, Internet Systems Consortium
3399.18.11 NSUPDATE(1)