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  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

       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 authenti-
       cating 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  sup-
       plied 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  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

       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 choosen by the system.  port can addition-
              ally 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.

       key name secret
              Specifies that all updates are to be TSIG signed using the  key-
              name  keysecret  pair.  The key command overrides any key speci-
              fied 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 exist-
              ing  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 sup-
              plied. The ttl is ignored, and is only allowed  for  compatibil-

       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  prerequi-
              sites 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 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 A
       > update add 86400 A

       Any A records for are deleted.  and an A record for it IP address is added.  The newly-added
       record has a 1 day TTL (86400 seconds)

       # nsupdate
       > prereq nxdomain
       > update add 86400 CNAME

       The prerequisite condition gets the name server to check that there are
       no  resource  records  of  any type for  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)