Provided by: dnsutils_9.3.2-2ubuntu1_i386 bug

NAME

       nsupdate - Dynamic DNS update utility

SYNOPSIS

       nsupdate [-d] [[-y keyname:secret] [-k keyfile]] [-t timeout]
                [-u udptimeout] [-r udpretries] [-v] [filename]

DESCRIPTION

       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
       record.

       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
       or the SIG(0) record described in RFC3535 and RFC2931. TSIG relies 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. 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.  nsupdate does not
       read /etc/named.conf.

       nsupdate uses the -y or -k option (with an HMAC-MD5 key) 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 shell.

       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.

       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. The -v option makes nsupdate use a TCP connection. This
       may be preferable when a batch of update requests is made.

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

       The -u option sets 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.

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

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:

              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.

              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.

              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.

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

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

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

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

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

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

              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.

              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.

              Adds a new resource record with the specified
                  ttl, class and data.

              Displays the current message, containing all of the
                   prerequisites and updates specified since the last send.

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

              Displays the answer.

       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 it 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 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 RRSIG, DNSKEY and
       NSEC records.)

FILES

       /etc/resolv.conf
              used to identify default name server

       K{name}.+157.+{random}.key
              base-64 encoding of HMAC-MD5 key created by dnssec-keygen(8).

       K{name}.+157.+{random}.private
              base-64 encoding of HMAC-MD5 key created by dnssec-keygen(8).

SEE ALSO

       RFC2136(), RFC3007(), RFC2104(), RFC2845(), RFC1034(), RFC2535(),
       RFC2931(), named(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.