NSUPDATE(8)															       NSUPDATE(8)

NAME

       nsupdate - Dynamic DNS update utility

SYNOPSIS

       nsupdate [ -d ]	[  [ -y keyname:secret ]  [ -k keyfile ]  ]  [ -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 mas-
       ter 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 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.  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 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.

       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.

INPUT FORMAT

       nsupdate reads input from filename or standard input.  Each command is supplied on exactly one line of input.  Some commands are for admin-
       istrative purposes.  The others are either update instructions or prerequisite checks on the contents of the zone.  These checks set condi-
       tions  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 choosen by the system.  port can additionally be used to make requests come from a specific port.  If no port  num-
	      ber 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.

       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.

       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
       >

       Any A records for oldhost.example.com are deleted.  and an A record for newhost.example.com it 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
       >

       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.)

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, 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.

BIND9								   Jun 30, 2000 						       NSUPDATE(8)