NSUPDATE(8)                          BIND9                         NSUPDATE(8)



NAME
       nsupdate - Dynamic DNS update utility

SYNOPSIS
       nsupdate [-d] [[-y [hmac:]keyname:secret] | [-k keyfile]] [-t timeout]
                [-u udptimeout] [-r udpretries] [-R randomdev] [-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
       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
       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/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/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, default type HMAC-MD5. 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
       [hmac:]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.

       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.

       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. The -v option makes nsupdate use a TCP connection. This
       may be preferable when a batch of update requests is made.

       The -t option sets 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.

       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.

       The -R randomdev option specifies a source of randomness. If the
       operating system does not provide a /dev/random or equivalent device,
       the default source of randomness is keyboard input.  randomdev
       specifies the name of a character device or file containing random data
       to be used instead of the default. The special value keyboard indicates
       that keyboard input should be used. This option may be specified
       multiple times.

INPUT FORMAT
       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 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 determine 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}
           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.

       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 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 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.

COPYRIGHT
       Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
       Copyright (C) 2000-2003 Internet Software Consortium.



BIND9                            Jun 30, 2000                      NSUPDATE(8)
