NSUPDATE(8)                                                        NSUPDATE(8)

       nsupdate - Dynamic DNS update utility

       nsupdate [ -d ]  [  [ -y keyname:secret ]  [ -k keyfile ]  ]  [ -v ]  [
       filename ]

       nsupdate is used to submit Dynamic DNS Update requests as defined in
       RFC2136 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

       The -d option makes nsupdate operate in debug mode.  This provides
       tracing information about the update requests that are made and the
       replies received from the name server.

       Transaction signatures can be used to authenticate the Dynamic DNS
       updates.  These use the TSIG resource record type described in RFC2845.
       The signatures rely on a shared secret that should only be known to
       nsupdate and the name server.  Currently, the only supported encryption
       algorithm for TSIG is HMAC-MD5, which is defined in RFC 2104.  Once
       other algorithms are defined for TSIG, applications will need to ensure
       they select the appropriate algorithm as well as the key when
       authenticating each other.  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.  nsupdate does not read /etc/named.conf.

       nsupdate uses the -y or -k option to provide the shared secret needed
       to generate a TSIG record for authenticating Dynamic DNS update
       requests.  These options are mutually exclusive.  With the -k option,
       nsupdate reads the shared secret from the file keyfile, whose name is
       of the form K{name}.+157.+{random}.private.  For historical reasons,
       the file K{name}.+157.+{random}.key must also be present. When the -y
       option is used, a signature is generated from keyname:secret.  keyname
       is the name of the key, and secret is the base64 encoded shared secret.
       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 ps(1) or in a history file maintained by the user's

       By default nsupdate uses UDP to send update requests to the name
       server.  The -v option makes nsupdate use a TCP connection.  This may
       be preferable when a batch of update requests is made.

       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

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

       key name secret
              Specifies that all updates are to be TSIG signed using the
              keyname keysecret pair.  The key command overrides any key
              specified on the command line via -y or -k.

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

       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

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

       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.

       Lines beginning with a semicolon are comments and are ignored.

       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

       # 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 it IP address 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 RFC1034 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 RFC2535 to allow CNAMEs to have SIG, KEY and
       NXT records.)

              used to identify default name server

              base-64 encoding of HMAC-MD5 key created by dnssec-keygen(8).

              base-64 encoding of HMAC-MD5 key created by dnssec-keygen(8).

       RFC2136, RFC3007, RFC2104, RFC2845, RFC1034, RFC2535, named(8), dnssec-

       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.

BIND9                            Jun 30, 2000                      NSUPDATE(8)