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NSUPDATE(1)                                   BIND 9                                  NSUPDATE(1)

NAME
       nsupdate - dynamic DNS update utility

SYNOPSIS
       nsupdate [-d] [-D] [-i] [-L level] [ [-g] | [-o] | [-l] | [-y [hmac:]keyname:secret] | [-k
       keyfile] ] [-t timeout] [-u udptimeout] [-r udpretries] [-v] [-T] [-P] [-V] [ [-4] |  [-6]
       ] [filename]

DESCRIPTION
       nsupdate  is used to submit Dynamic DNS Update requests, as defined in RFC 2136, to a name
       server. This allows resource records to be added or removed from a zone  without  manually
       editing  the zone file. A single update request can contain requests to add or remove more
       than one resource record.

       Zones that are under dynamic control via nsupdate or a DHCP server should not be edited by
       hand. Manual edits could conflict with dynamic updates and cause data to be lost.

       The  resource  records  that are dynamically added or removed with nsupdate must be in the
       same zone. Requests are sent to the zone's primary server,  which  is  identified  by  the
       MNAME field of the zone's SOA record.

       Transaction  signatures can be used to authenticate the Dynamic DNS updates. These use the
       TSIG resource record type described in RFC 2845, the SIG(0) record described in  RFC  2535
       and RFC 2931, or GSS-TSIG as described in RFC 3645.

       TSIG  relies on a shared secret that should only be known to nsupdate and the name server.
       For instance, suitable key and server statements are added to /etc/named.conf so that  the
       name  server can associate the appropriate secret key and algorithm with the IP address of
       the client application that is using TSIG authentication. ddns-confgen can generate  suit-
       able  configuration  fragments.  nsupdate  uses  the  -y or -k options to provide the TSIG
       shared secret; these options are mutually exclusive.

       SIG(0) uses public key cryptography. To use a SIG(0) key, the public key must be stored in
       a KEY record in a zone served by the name server.

       GSS-TSIG  uses  Kerberos  credentials.  Standard  GSS-TSIG mode is switched on with the -g
       flag. A non-standards-compliant variant of GSS-TSIG used by Windows 2000 can  be  switched
       on with the -o flag.

OPTIONS
       -4     This option sets use of IPv4 only.

       -6     This option sets use of IPv6 only.

       -d     This  option  sets  debug mode, which provides tracing information about the update
              requests that are made and the replies received from the name server.

       -D     This option sets extra debug mode.

       -i     This option forces interactive mode, even when standard input is not a terminal.

       -k keyfile
              This option indicates the file containing the TSIG authentication key. Keyfiles may
              be  in  two  formats:  a  single file containing a named.conf-format key statement,
              which may be generated automatically by ddns-confgen; or  a  pair  of  files  whose
              names  are of the format K{name}.+157.+{random}.key and K{name}.+157.+{random}.pri-
              vate, which can be generated by dnssec-keygen. The -k option can also  be  used  to
              specify  a  SIG(0)  key  used  to authenticate Dynamic DNS update requests. In this
              case, the key specified is not an HMAC-MD5 key.

       -l     This option sets local-host only mode, which sets the server address  to  localhost
              (disabling the server so that the server address cannot be overridden). Connections
              to the local server use a TSIG key found in  /var/run/named/session.key,  which  is
              automatically generated by named if any local primary zone has set update-policy to
              local. The location of this key file can be overridden with the -k option.

       -L level
              This option sets the logging debug level. If zero, logging is disabled.

       -p port
              This option sets the port to use for connections to a name server. The  default  is
              53.

       -P     This  option  prints  the list of private BIND-specific resource record types whose
              format is understood by nsupdate. See also the -T option.

       -r udpretries
              This option sets the number of UDP retries. The default is 3. If zero, only one up-
              date request is made.

       -t timeout
              This  option sets the maximum time an update request can take before it is aborted.
              The default is 300 seconds. If zero, the timeout is disabled.

       -T     This option prints the list of IANA standard resource record types whose format  is
              understood  by  nsupdate. nsupdate exits after the lists are printed. The -T option
              can be combined with the -P option.

              Other types can be entered using TYPEXXXXX where XXXXX is the decimal value of  the
              type  with  no  leading  zeros.  The rdata, if present, is parsed using the UNKNOWN
              rdata format, (<backslash> <hash> <space> <length> <space> <hexstring>).

       -u udptimeout
              This option sets the UDP retry interval. The default is 3 seconds. If zero, the in-
              terval is computed from the timeout interval and number of UDP retries.

       -v     This  option  specifies  that TCP should be used even for small update requests. By
              default, nsupdate uses UDP to send update requests to the name server  unless  they
              are  too  large  to  fit  in  a  UDP request, in which case TCP is used. TCP may be
              preferable when a batch of update requests is made.

       -V     This option prints the version number and exits.

       -y [hmac:]keyname:secret
              This option sets the literal TSIG authentication key. keyname is the  name  of  the
              key,  and  secret  is the base64 encoded shared secret. hmac is the name of the key
              algorithm;  valid  choices  are  hmac-md5,  hmac-sha1,  hmac-sha224,   hmac-sha256,
              hmac-sha384,  or hmac-sha512. If hmac is not specified, the default is hmac-md5, or
              if MD5 was disabled, hmac-sha256.

              NOTE: Use of the -y option is discouraged because the shared secret is supplied  as
              a  command-line  argument in clear text. This may be visible in the output from ps1
              or in a history file maintained by the user's shell.

INPUT FORMAT
       nsupdate reads input from filename or standard input. Each command is supplied on  exactly
       one line of input. Some commands are for administrative purposes; others are either update
       instructions or prerequisite checks on the contents of the zone. These checks  set  condi-
       tions  that  some  name or set of resource records (RRset) either exists or is absent from
       the zone. These conditions must be met if the entire update request is to succeed. Updates
       are rejected if the tests for the prerequisite conditions fail.

       Every update request consists of zero or more prerequisites and zero or more updates. This
       allows a suitably authenticated update request  to  proceed  if  some  specified  resource
       records  are either present or missing from the zone. A blank input line (or the send com-
       mand) causes the accumulated commands to be sent as one Dynamic DNS update request to  the
       name server.

       The command formats and their meanings are as follows:

       server servername port
              This command sends all dynamic update requests to the name server servername.  When
              no server statement is provided, nsupdate sends updates to the  primary  server  of
              the  correct  zone.  The MNAME field of that zone's SOA record identify the primary
              server for that zone.  port is the port number on servername where the dynamic  up-
              date requests are sent. If no port number is specified, the default DNS port number
              of 53 is used.

              NOTE:
                 This command has no effect when GSS-TSIG is in use.

       local address port
              This command sends all dynamic update requests using the local address. When no lo-
              cal  statement is provided, nsupdate sends updates using an address and port chosen
              by the system. port can also be used to force requests  to  come  from  a  specific
              port. If no port number is specified, the system assigns one.

       zone zonename
              This command specifies that all updates are to be made to the zone zonename.  If no
              zone statement is provided, nsupdate attempts to determine the correct zone to  up-
              date based on the rest of the input.

       class classname
              This  command  specifies  the  default class. If no class is specified, the default
              class is IN.

       ttl seconds
              This command specifies the default time-to-live, in  seconds,  for  records  to  be
              added. The value none clears the default TTL.

       key hmac:keyname secret
              This command specifies that all updates are to be TSIG-signed using the keyname-se-
              cret pair. If hmac is specified, it sets the signing algorithm in use. The  default
              is hmac-md5; if MD5 was disabled, the default is hmac-sha256. The key command over-
              rides any key specified on the command line via -y or -k.

       gsstsig
              This command uses GSS-TSIG to sign the updates. This is equivalent to specifying -g
              on the command line.

       oldgsstsig
              This command uses the Windows 2000 version of GSS-TSIG to sign the updates. This is
              equivalent to specifying -o on the command line.

       realm [realm_name]
              When using GSS-TSIG, this command specifies the use of realm_name rather  than  the
              default realm in krb5.conf. If no realm is specified, the saved realm is cleared.

       check-names [yes_or_no]
              This  command  turns  on  or  off  check-names  processing  on records to be added.
              Check-names has no effect on prerequisites or records to be  deleted.   By  default
              check-names  processing  is  on. If check-names processing fails, the record is not
              added to the UPDATE message.

       prereq nxdomain domain-name
              This command requires that no resource record of any type exist with the  name  do-
              main-name.

       prereq yxdomain domain-name
              This  command  requires that domain-name exist (as at least one resource record, of
              any type).

       prereq nxrrset domain-name class type
              This command requires that no resource record exist of the specified  type,  class,
              and domain-name. If class is omitted, IN (Internet) is assumed.

       prereq yxrrset domain-name class type
              This  command  requires that a resource record of the specified type, class and do-
              main-name exist. If class is omitted, IN (internet) is assumed.

       prereq yxrrset domain-name class type data
              With this command, the data from each set of prerequisites of this form  sharing  a
              common  type, class, and domain-name are combined to form a set of RRs. This set of
              RRs must exactly match the set of RRs existing in  the  zone  at  the  given  type,
              class, and domain-name. The data are written in the standard text representation of
              the resource record's RDATA.

       update delete domain-name ttl class type data
              This command deletes any resource records named domain-name. If type and  data  are
              provided,  only  matching  resource records are removed.  The Internet class is as-
              sumed if class is not supplied. The ttl is ignored, and is only allowed for compat-
              ibility.

       update add domain-name ttl class type data
              This command adds a new resource record with the specified ttl, class, and data.

       show   This  command displays the current message, containing all of the prerequisites and
              updates specified since the last send.

       send   This command sends the current message. This is  equivalent  to  entering  a  blank
              line.

       answer This command displays the answer.

       debug  This command turns on debugging.

       version
              This command prints the version number.

       help   This command prints a list of commands.

       Lines beginning with a semicolon (;) are comments and are ignored.

EXAMPLES
       The  examples  below  show  how nsupdate can be used to insert and delete resource records
       from the example.com zone. Notice that the input in each example contains a trailing blank
       line,  so  that  a  group of commands is sent as one dynamic update request to the primary
       name server for example.com.

          # nsupdate
          > update delete oldhost.example.com A
          > update add newhost.example.com 86400 A 172.16.1.1
          > send

       Any A records for oldhost.example.com are deleted, and an A record for newhost.example.com
       with IP address 172.16.1.1 is added. The newly added record has a TTL of 1 day (86400 sec-
       onds).

          # nsupdate
          > prereq nxdomain nickname.example.com
          > update add nickname.example.com 86400 CNAME somehost.example.com
          > send

       The prerequisite condition tells the name server to verify  that  there  are  no  resource
       records  of  any type for nickname.example.com. If there are, the update request fails. If
       this name does not exist, a CNAME for it is added. This ensures that  when  the  CNAME  is
       added, it cannot conflict with the long-standing rule in RFC 1034 that a name must not ex-
       ist as any other record type if it exists as a CNAME.  (The  rule  has  been  updated  for
       DNSSEC in RFC 2535 to allow CNAMEs to have RRSIG, DNSKEY, and NSEC records.)

FILES
       /etc/resolv.conf
              Used to identify the default name server

       /var/run/named/session.key
              Sets the default TSIG key for use in local-only mode

       K{name}.+157.+{random}.key
              Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.

       K{name}.+157.+{random}.private
              Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.

SEE ALSO
       RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931, named(8), ddns-conf-
       gen(8), dnssec-keygen(8).

BUGS
       The TSIG key is redundantly stored in two separate files. This is a consequence  of  nsup-
       date  using the DST library for its cryptographic operations, and may change in future re-
       leases.

AUTHOR
       Internet Systems Consortium

COPYRIGHT
       2024, Internet Systems Consortium

9.16.48-Ubuntu                              2024-02-11                                NSUPDATE(1)

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