NSUPDATE(1)



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  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 have to be in the same zone. Requests are sent to the zone's  mas-
       ter  server.  This  is  identified by the MNAME field of the zone's SOA
       record.

       Transaction signatures can be used to authenticate the Dynamic DNS  up-
       dates. These use the TSIG resource record type described in RFC 2845 or
       the SIG(0) record described in RFC 2535 and RFC 2931 or GSS-TSIG as de-
       scribed 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
       would be 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 will be using TSIG authentication. You can use
       ddns-confgen to generate  suitable  configuration  fragments.  nsupdate
       uses  the -y or -k options to provide the TSIG shared secret. These op-
       tions 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     Use IPv4 only.

       -6     Use IPv6 only.

       -d     Debug  mode.  This provides tracing information about the update
              requests that are made and the replies received  from  the  name
              server.

       -D     Extra debug mode.

       -i     Force interactive mode, even when standard input is not a termi-
              nal.

       -k keyfile
              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}.private,
              which can be generated by dnssec-keygen. The -k may 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     Local-host only mode. This sets the server address to  localhost
              (disabling the server so that the server address cannot be over-
              ridden). Connections to the local server will  use  a  TSIG  key
              found in /var/run/named/session.key, which is automatically gen-
              erated by named if any local master zone has  set  update-policy
              to  local.  The location of this key file can be overridden with
              the -k option.

       -L level
              Set the logging debug level. If zero, logging is disabled.

       -p port
              Set the port to use for connections to a name  server.  The  de-
              fault is 53.

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

       -r udpretries
              The number of UDP retries. The default is 3. If zero,  only  one
              update request will be made.

       -t timeout
              The  maximum  time  an  update  request  can  take  before it is
              aborted. The default is 300 seconds. Zero can be used to disable
              the timeout.

       -T     Print the list of IANA standard resource record types whose for-
              mat is understood by nsupdate.  nsupdate  will  exit  after  the
              lists are printed. The -T option can be combined with the -P op-
              tion.

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

       -u udptimeout
              The  UDP  retry interval. The default is 3 seconds. If zero, the
              interval will be computed from the timeout interval  and  number
              of UDP retries.

       -v     Use  TCP  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 will be
              used. TCP may be preferable when a batch of update  requests  is
              made.

       -V     Print the version number and exit.

       -y [hmac:]keyname:secret
              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 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.

INPUT FORMAT
       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. The others are either update instructions or prereq-
       uisite 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
       request  is  to  succeed. Updates will be 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 present or missing  from
       the  zone.  A blank input line (or the send command) causes the accumu-
       lated commands to be sent as one Dynamic DNS update request to the name
       server.

       The command formats and their meaning are as follows:

       server servername port
              Sends all dynamic update requests to the name server servername.
              When no server statement is provided, nsupdate will send updates
              to  the  master  server  of the correct zone. The MNAME field of
              that zone's SOA record will identify the master server for  that
              zone.   port  is the port number on servername where the dynamic
              update requests get sent. If no port number  is  specified,  the
              default DNS port number of 53 is used.

       local address port
              Sends  all dynamic update requests using the local address. When
              no local statement is provided, nsupdate will send updates using
              an  address and port chosen by the system. port can additionally
              be used to make requests come from a specific port. If  no  port
              number is specified, the system will assign one.

       zone zonename
              Specifies  that all updates are to be made to the zone zonename.
              If no zone statement is provided, nsupdate will  attempt  deter-
              mine the correct zone to update based on the rest of the input.

       class classname
              Specify the default class. If no class is specified, the default
              class is IN.

       ttl seconds
              Specify the default time to live for records to  be  added.  The
              value none will clear the default ttl.

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

       gsstsig
              Use GSS-TSIG to sign the updated. This is equivalent to specify-
              ing -g on the command line.

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

       realm [realm_name]
              When using GSS-TSIG use 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]
              Turn  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 will not be added to the
              UPDATE message.

       prereq nxdomain domain-name
              Requires  that  no  resource record of any type exists with name
              domain-name.

       prereq yxdomain domain-name
              Requires that domain-name exists (has as at least  one  resource
              record, of any type).

       prereq nxrrset domain-name class type
              Requires  that  no resource record exists of the specified type,
              class and domain-name. If class is omitted, IN (internet) is as-
              sumed.

       prereq yxrrset domain-name class type
              This  requires  that  a  resource  record of the specified type,
              class and domain-name must exist. If class is omitted,  IN  (in-
              ternet) is assumed.

       prereq yxrrset domain-name class type data
              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 exist-
              ing in the zone at the given type, class, and  domain-name.  The
              data  are written in the standard text representation of the re-
              source record's RDATA.

       update delete domain-name ttl class type data
              Deletes any resource records named domain-name. If type and data
              is  provided,  only  matching  resource records will be removed.
              The internet class is assumed if class is not supplied. The  ttl
              is ignored, and is only allowed for compatibility.

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

       show   Displays the current message, containing all  of  the  prerequi-
              sites and updates specified since the last send.

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

       answer Displays the answer.

       debug  Turn on debugging.

       version
              Print version number.

       help   Print a list of commands.

       Lines beginning with a semicolon are comments and are ignored.

EXAMPLES
       The examples below show how nsupdate could 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
       are  sent  as  one dynamic update request to the master 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 1 day TTL (86400 seconds).

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

       The prerequisite condition gets the name server to check 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  exist  as
       any  other  record type if it exists as a CNAME. (The rule has been up-
       dated for DNSSEC in RFC 2535 to allow CNAMEs to have RRSIG, DNSKEY  and
       NSEC records.)

FILES
       /etc/resolv.conf
              used to identify 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 HMAC-MD5 key created by dnssec-keygen8.

       K{name}.+157.+{random}.private
              base-64 encoding of HMAC-MD5 key created by dnssec-keygen8.

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

BUGS
       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.

AUTHOR
       Internet Systems Consortium

COPYRIGHT
       2020, Internet Systems Consortium

9.16.8-Debian                     2020-10-13                       NSUPDATE(1)

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