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NSUPDATE(8)									      NSUPDATE(8)

       nsupdate - Dynamic DNS update utility

       nsupdate [ -d ]	[  [ -y keyname:secret ]  [ -k keyfile ]  ]  [ -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 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.  The signatures rely 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 algo-
       rithms 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  asso-
       ciate  the appropriate secret key and algorithm with the IP address of the client applica-
       tion that will be using TSIG authentication.  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.	These options are mutually exclu-
       sive.  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.

       By default nsupdate uses UDP to send update requests to the name server.   The  -v  option
       makes  nsupdate	use  a	TCP  connection.   This  may be preferable when a batch of update
       requests is 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

       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  cor-
	      rect  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 choosen 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 state-
	      ment is provided, nsupdate will attempt determine the correct zone to update  based
	      on the rest of the input.

       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

       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 spec-
	      ified since the last send.

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

       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  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  mas-
       ter name server for example.com.

       # nsupdate
       > update delete oldhost.example.com A
       > update add newhost.example.com 86400 A

       Any  A  records	for  oldhost.example.com  are deleted.	and an A record for newhost.exam-
       ple.com it IP address is added.  The newly-added record has a 1 day TTL  (86400

       # nsupdate
       > prereq nxdomain nickname.example.com
       > update add nickname.example.com 86400 CNAME somehost.example.com

       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 SIG, KEY and NXT 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, named(8), dnssec-keygen(8).

       The TSIG key is redundantly stored in two separate files.  This is a consequence of  nsup-
       date  using  the  DST  library  for its cryptographic operations, and may change in future

BIND9					   Jun 30, 2000 			      NSUPDATE(8)
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