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NSUPDATE(1)			    BIND 9			   NSUPDATE(1)

NAME
       nsupdate	- dynamic DNS update utility

SYNOPSIS
       nsupdate	 [-d]  [-D]  [-i]  [-L	level]	[  [-g]	 |  [-o]  | [-l] | [-y
       [hmac:]keyname:secret] |	[-k keyfile] ] [-t  timeout]  [-u  udptimeout]
       [-r udpretries] [-v] [-T] [-P] [-V] [ [-4] | [-6] ] [filename]

DESCRIPTION
       nsupdate	 is  used  to submit Dynamic DNS Update	requests as defined in
       RFC 2136	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  re-
       source 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
       record.

       Transaction signatures can be used to authenticate the Dynamic DNS  up-
       dates. These use	the TSIG resource record type described	in RFC 2845 or
       the SIG(0) record described in RFC 2535 and RFC 2931 or GSS-TSIG	as de-
       scribed in RFC 3645.

       TSIG  relies  on	 a shared secret that should only be known to nsupdate
       and the name server. For	instance, suitable key and  server  statements
       would  be  added	 to  /usr/local/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 authenti-
       cation. You can use ddns-confgen	 to  generate  suitable	 configuration
       fragments.  nsupdate  uses  the	-y  or	-k options to provide the TSIG
       shared secret. These options are	mutually exclusive.

       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.

       GSS-TSIG	 uses Kerberos credentials. Standard GSS-TSIG mode is switched
       on with the -g flag. A non-standards-compliant variant of GSS-TSIG used
       by Windows 2000 can be switched on with the -o flag.

OPTIONS
       -4     Use IPv4 only.

       -6     Use IPv6 only.

       -d     Debug  mode.  This provides tracing information about the	update
	      requests that are	made and the replies received  from  the  name
	      server.

       -D     Extra debug mode.

       -i     Force interactive	mode, even when	standard input is not a	termi-
	      nal.

       -k keyfile
	      The file containing the TSIG authentication key. Keyfiles	may be
	      in two formats: a	single file containing a named.conf-format key
	      statement, which may be generated	automatically by ddns-confgen,
	      or   a   pair   of   files   whose   names  are  of  the	format
	      K{name}.+157.+{random}.key  and  K{name}.+157.+{random}.private,
	      which can	be generated by	dnssec-keygen. 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.

       -l     Local-host only mode. This sets the server address to  localhost
	      (disabling the server so that the	server address cannot be over-
	      ridden). Connections to the local	server will  use  a  TSIG  key
	      found in /var/run/named/session.key, which is automatically gen-
	      erated by	named if any local master zone has  set	 update-policy
	      to  local.  The location of this key file	can be overridden with
	      the -k option.

       -L level
	      Set the logging debug level. If zero, logging is disabled.

       -p port
	      Set the port to use for connections to a name  server.  The  de-
	      fault is 53.

       -P     Print  the  list	of private BIND-specific resource record types
	      whose format is understood by nsupdate. See also the -T option.

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

       -t timeout
	      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.

       -T     Print the	list of	IANA standard resource record types whose for-
	      mat is understood	by nsupdate.  nsupdate	will  exit  after  the
	      lists are	printed. The -T	option can be combined with the	-P op-
	      tion.

	      Other types can be entered using "TYPEXXXXX"  where  "XXXXX"  is
	      the  decimal value of the	type with no leading zeros. The	rdata,
	      if present, will be  parsed  using  the  UNKNOWN	rdata  format,
	      (<backslash> <hash> <space> <length> <space> <hexstring>).

       -u udptimeout
	      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.

       -v     Use  TCP	even  for  small update	requests. 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. TCP	may be preferable when a batch of update  requests  is
	      made.

       -V     Print the	version	number and exit.

       -y [hmac:]keyname:secret
	      Literal TSIG authentication key. keyname is the name of the key,
	      and secret is the	base64 encoded shared secret. hmac is the name
	      of  the  key  algorithm;	valid choices are hmac-md5, hmac-sha1,
	      hmac-sha224, hmac-sha256,	hmac-sha384, or	hmac-sha512.  If  hmac
	      is not specified,	the default is hmac-md5	or if MD5 was disabled
	      hmac-sha256.

	      NOTE: Use	of the -y option is discouraged	because	the shared se-
	      cret  is supplied	as a command line argument in clear text. This
	      may be visible in	the output from	ps1 or in a history file main-
	      tained by	the user's shell.

INPUT FORMAT
       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
       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	deter-
	      mine 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.

       ttl seconds
	      Specify the default time to live for records to  be  added.  The
	      value none will clear the	default	ttl.

       key hmac:keyname	secret
	      Specifies	 that all updates are to be TSIG-signed	using the key-
	      name secret pair.	If hmac	is specified, then it sets the signing
	      algorithm	in use;	the default is hmac-md5	or if MD5 was disabled
	      hmac-sha256. The key command overrides any key specified on  the
	      command line via -y or -k.

       gsstsig
	      Use GSS-TSIG to sign the updated.	This is	equivalent to specify-
	      ing -g on	the command line.

       oldgsstsig
	      Use the Windows 2000 version of GSS-TSIG to  sign	 the  updated.
	      This is equivalent to specifying -o on the command line.

       realm [realm_name]
	      When using GSS-TSIG use realm_name rather	than the default realm
	      in krb5.conf. If no  realm  is  specified	 the  saved  realm  is
	      cleared.

       check-names [yes_or_no]
	      Turn  on	or  off	check-names processing on records to be	added.
	      Check-names has no effect	on  prerequisites  or  records	to  be
	      deleted.	  By   default	 check-names   processing  is  on.  If
	      check-names processing fails the record will not be added	to the
	      UPDATE message.

       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 as-
	      sumed.

       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  (in-
	      ternet) 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 re-
	      source 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  prerequi-
	      sites and	updates	specified since	the last send.

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

       answer Displays the answer.

       debug  Turn on debugging.

       version
	      Print version number.

       help   Print a list of commands.

       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 RFC 1034 that a name must	not  exist  as
       any  other  record type if it exists as a CNAME.	(The rule has been up-
       dated for DNSSEC	in RFC 2535 to allow CNAMEs to have RRSIG, DNSKEY  and
       NSEC records.)

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

       /var/run/named/session.key
	      sets the default TSIG key	for use	in local-only mode

       K{name}.+157.+{random}.key
	      base-64 encoding of HMAC-MD5 key created by dnssec-keygen8.

       K{name}.+157.+{random}.private
	      base-64 encoding of HMAC-MD5 key created by dnssec-keygen8.

SEE ALSO
       RFC  2136,  RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931,
       named(8), ddns-confgen(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 op-
       erations, and may change	in future releases.

AUTHOR
       Internet	Systems	Consortium

COPYRIGHT
       2020, Internet Systems Consortium

9.16.6				  2020-08-10			   NSUPDATE(1)

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

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