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NAME    [Toc]    [Back]

       nsupdate - Dynamic DNS update utility

SYNOPSIS    [Toc]    [Back]

       nsupdate [ -d ]	[  [ -y keyname:secret ]  [ -k keyfile ]  ]  [ -v ]  [
       filename ]

DESCRIPTION    [Toc]    [Back]

       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 master
 server.  This is identified by the MNAME field of  the  zone's  SOA

       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

       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    [Toc]    [Back]

       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 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 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.

       key name secret
	      Specifies that all updates are to be TSIG signed using the  key-
	      name  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

       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

       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

       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    [Toc]    [Back]

       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

       # 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.example.com it IP address 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    [Toc]    [Back]

	      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).

SEE ALSO    [Toc]    [Back]

       RFC2136, RFC3007, RFC2104, RFC2845, RFC1034, RFC2535, named(8), dnssec-

BUGS    [Toc]    [Back]

       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)
[ Back ]
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