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NSUPDATE(8)			     BIND9			   NSUPDATE(8)

       nsupdate	- Dynamic DNS update utility

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

       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.

       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

	      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

	      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

	      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.

       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
       > send

       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
       > send

       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 RRSIG, DNSKEY and
       NSEC 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(),
       RFC2931(), named(8), dnssec-keygen(8).

       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)


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