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nsupdate(8)

NAME

       nsupdate - Dynamic DNS update utility

SYNOPSIS

       nsupdate  [  -d	]   [	[ -y 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  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.

       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 key-
       file,  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 key-
       name: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 main-
       tained by the user's shell.
       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
       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 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.

       key name secret
       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 exist-
	      ing  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 sup-
	      plied. The ttl is ignored, and is only allowed  for  compatibil-
	      ity.

       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.

       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 it IP address 172.16.1.1 is added.  The newly-added
       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.

BIND9				 Jun 30, 2000			   NSUPDATE(8)

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