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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/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 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, 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:

       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 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
	   > 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			   NSUPDATE(8)

NAME | SYNOPSIS | DESCRIPTION | INPUT FORMAT | EXAMPLES | FILES | SEE ALSO | BUGS | COPYRIGHT

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