


NSUPDATE(8)                   BIND9                   NSUPDATE(8)


NAME
       nsupdate - Dynamic DNS update utility

SYNOPSIS
       nsupdate [-d] [[-y [hmac:]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 to provide the shared
       secret needed to generate a TSIG record for authenticating
       Dynamic DNS update requests, default type HMAC-MD5. These
       options are mutually exclusive. With the -k option,



BIND9                      Jun 30, 2000                         1





NSUPDATE(8)                   BIND9                   NSUPDATE(8)


       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
       [hmac:]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 an 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:



BIND9                      Jun 30, 2000                         2





NSUPDATE(8)                   BIND9                   NSUPDATE(8)


       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.

       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 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



BIND9                      Jun 30, 2000                         3





NSUPDATE(8)                   BIND9                   NSUPDATE(8)


           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.

       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



BIND9                      Jun 30, 2000                         4





NSUPDATE(8)                   BIND9                   NSUPDATE(8)


           > 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.

COPYRIGHT
       Copyright (C) 2004-2007 Internet Systems Consortium, Inc.
       ("ISC")
       Copyright (C) 2000-2003 Internet Software Consortium.

















BIND9                      Jun 30, 2000                         5


