nsupdate

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
       have to be in the same zone. Requests are sent to the zone's master
       server. This 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 or
       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 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 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     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
              terminal.

       -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
              overridden). Connections to the local server will use a TSIG key
              found in /var/run/named/session.key, which is automatically
              generated 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 default
              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 format
              is understood by nsupdate. nsupdate will exit 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, 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
              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. The 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 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 accumulated
       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 determine
              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 keyname
              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 specifying
              -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
              assumed.

       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 (internet) 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 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
              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 prerequisites
              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 updated 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
       operations, and may change in future releases.

AUTHOR
       Internet Systems Consortium

COPYRIGHT
       2020, Internet Systems Consortium



9.16.10                            2020-12-21                        NSUPDATE(1)