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NSUPDATE(1)                         BIND 9                         NSUPDATE(1)

       nsupdate - dynamic DNS update utility

       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]

       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  re-
       source 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 nsup-
       date 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

       Transaction signatures can be used to authenticate the Dynamic DNS  up-
       dates.  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/bind/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 suitable configuration fragments. nsupdate uses the -y  or  -k
       options  to  provide the TSIG shared secret; these options are mutually

       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.

       -4     This option sets use of IPv4 only.

       -6     This option sets use of IPv6 only.

       -C     Overrides  the  default  resolv.conf file. This is only intended
              for testing.

       -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.

       -g     This option enables standard GSS-TSIG 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 authentica-
              tion key. Keyfiles may be in two formats: a single file contain-
              ing  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}.private,  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 ad-
              dress to localhost (disabling the server so that the server  ad-
              dress cannot be overridden). Connections to the local server use
              a TSIG key found in  /run/session.key,  which  is  automatically
              generated by named if any local primary zone has set update-pol-
              icy 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

       -o     This  option  enables  a  non-standards-compliant   variant   of
              GSS-TSIG used by Windows 2000.

       -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 update request is made.

       -t timeout
              This option sets the maximum time an update request can take be-
              fore 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 af-
              ter  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 sec-
              onds. If zero, the interval is computed from the timeout  inter-
              val and number of UDP retries.

       -v     This option specifies that TCP should be used even for small up-
              date requests. By default, nsupdate uses UDP to send update  re-
              quests  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 se-
              cret.  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 se-
              cret  is supplied as a command-line argument in clear text. This
              may be visible in the output from ps1 or in a history file main-
              tained by the user's shell.

       nsupdate  reads  input from filename or standard input. Each command is
       supplied on exactly one line of input. Some commands are  for  adminis-
       trative purposes; others are either update instructions or prerequisite
       checks on the contents of the zone. These checks  set  conditions  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  re-
       quest  is to succeed. Updates are rejected if the tests for the prereq-
       uisite 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  miss-
       ing  from the zone. A blank input line (or the send command) 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,  nsup-
              date  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 update requests are sent. If no port number is
              specified, the default DNS port number of 53 is used.

                 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 local statement is provided, nsupdate sends up-
              dates  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  at-
              tempts to determine the correct zone to update based on the rest
              of the input.

       class classname
              This command specifies the default class. If no class is  speci-
              fied, 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-secret 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 overrides
              any key specified on the command line via -y or -k.

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

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

       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 [boolean]
              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 domain-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 spec-
              ified type, class, and domain-name. If class is omitted, IN (In-
              ternet) is assumed.

       prereq yxrrset domain-name class type
              This  command  requires  that a resource record of the specified
              type, class and domain-name exist. If class is omitted, IN  (in-
              ternet) 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 com-
              bined  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 rep-
              resentation 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 assumed if  class  is  not  sup-
              plied.  The  ttl is ignored, and is only allowed for compatibil-

       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.

              This command prints the version number.

       help   This command prints a list of commands.

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

       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 com-
       mands 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
          > send

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

          # 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  con-
       flict  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.)

              Used to identify the default name server

              Sets the default TSIG key for use in local-only mode

              Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.

              Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.

       RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535,  RFC  2931,
       named(8), dnssec-keygen(8), tsig-keygen(8).

       The  TSIG  key  is  redundantly stored in two separate files. This is a
       consequence of nsupdate using the DST library for its cryptographic op-
       erations, and may change in future releases.

       Internet Systems Consortium

       2023, Internet Systems Consortium

9.18.12-0ubuntu0.22.04.3-Ubuntu   2023-02-03                       NSUPDATE(1)
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