nsupdate

NSUPDATE(1)                          BIND9                         NSUPDATE(1)

NAME
       nsupdate - Dynamic DNS update utility

SYNOPSIS
       nsupdate [-d] [-D] [-i] [-L level] [[-g] | [-o] | [-l] |
                [-y [hmac:]keyname:secret] | [-k keyfile]] [-t timeout]
                [-u udptimeout] [-r udpretries] [-v] [-T] [-P] [-V] [[-4] |
                [-6]] [filename]

DESCRIPTION
       nsupdate is used to submit Dynamic DNS Update requests as defined in
       RFC 2136 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.

       Transaction signatures can be used to authenticate the Dynamic DNS
       updates. These use the TSIG resource record type described in RFC 2845
       or the SIG(0) record described in RFC 2535 and RFC 2931 or GSS-TSIG as
       described in RFC 3645.

       TSIG relies on a shared secret that should only be known to nsupdate
       and the name server. 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. You can use
       ddns-confgen to generate suitable configuration fragments.  nsupdate
       uses the -y or -k options to provide the TSIG shared secret. These
       options are mutually exclusive.

       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.

       GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode is switched
       on with the -g flag. A non-standards-compliant variant of GSS-TSIG used
       by Windows 2000 can be switched on with the -o flag.

OPTIONS
       -4
           Use IPv4 only.

       -6
           Use IPv6 only.

       -d
           Debug mode. This provides tracing information about the update
           requests that are made and the replies received from the name
           server.

       -D
           Extra debug mode.

       -i
           Force interactive mode, even when standard input is not a terminal.

       -k keyfile
           The file containing the TSIG authentication key. Keyfiles may be in
           two formats: a single file containing a named.conf-format key
           statement, which may be generated automatically by ddns-confgen, or
           a pair of files whose names are of the format
           K{name}.+157.+{random}.key and K{name}.+157.+{random}.private,
           which can be generated by dnssec-keygen. 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.

       -l
           Local-host only mode. This sets the server address to localhost
           (disabling the server so that the server address cannot be
           overridden). Connections to the local server will use a TSIG key
           found in /var/run/named/session.key, which is automatically
           generated by named if any local master zone has set update-policy
           to local. The location of this key file can be overridden with the
           -k option.

       -L level
           Set the logging debug level. If zero, logging is disabled.

       -p port
           Set the port to use for connections to a name server. The default
           is 53.

       -P
           Print the list of private BIND-specific resource record types whose
           format is understood by nsupdate. See also the -T option.

       -r udpretries
           The number of UDP retries. The default is 3. If zero, only one
           update request will be made.

       -t timeout
           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.

       -T
           Print the list of IANA standard resource record types whose format
           is understood by nsupdate.  nsupdate will exit after the lists are
           printed. The -T option can be combined with the -P option.

           Other types can be entered using "TYPEXXXXX" where "XXXXX" is the
           decimal value of the type with no leading zeros. The rdata, if
           present, will be parsed using the UNKNOWN rdata format,
           (<backslash> <hash> <space> <length> <space> <hexstring>).

       -u udptimeout
           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.

       -v
           Use TCP even for small update requests. 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. TCP
           may be preferable when a batch of update requests is made.

       -V
           Print the version number and exit.

       -y [hmac:]keyname:secret
           Literal TSIG authentication key.  keyname is the name of the key,
           and secret is the base64 encoded shared secret.  hmac is the name
           of the key algorithm; valid choices are hmac-md5, hmac-sha1,
           hmac-sha224, hmac-sha256, hmac-sha384, or hmac-sha512. If hmac is
           not specified, the default is hmac-md5 or if MD5 was disabled
           hmac-sha256.

           NOTE: 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.

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.

       ttl {seconds}
           Specify the default time to live for records to be added. The value
           none will clear the default ttl.

       key [hmac:] {keyname} {secret}
           Specifies that all updates are to be TSIG-signed using the
           keynamesecret pair. If hmac is specified, then it sets the signing
           algorithm in use; the default is hmac-md5 or if MD5 was disabled
           hmac-sha256. The key command overrides any key specified on the
           command line via -y or -k.

       gsstsig
           Use GSS-TSIG to sign the updated. This is equivalent to specifying
           -g on the command line.

       oldgsstsig
           Use the Windows 2000 version of GSS-TSIG to sign the updated. This
           is equivalent to specifying -o on the command line.

       realm {[realm_name]}
           When using GSS-TSIG use realm_name rather than the default realm in
           krb5.conf. If no realm is specified the saved realm is cleared.

       check-names {[yes_or_no]}
           Turn on or off check-names processing on records to be added.
           Check-names has no effect on prerequisites or records to be
           deleted. By default check-names processing is on. If check-names
           processing fails the record will not be added to the UPDATE
           message.

       [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] del[ete] {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.

       debug
           Turn on debugging.

       version
           Print version number.

       help
           Print a list of commands.

       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 RFC 1034 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 RFC 2535 to allow CNAMEs to have RRSIG, DNSKEY
       and NSEC records.)

FILES
       /etc/resolv.conf
           used to identify default name server

       /var/run/named/session.key
           sets the default TSIG key for use in local-only mode

       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
       RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931,
       named(8), ddns-confgen(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.

AUTHOR
       Internet Systems Consortium, Inc.

COPYRIGHT
       Copyright (C) 2000-2012, 2014-2020 Internet Systems Consortium, Inc.
       ("ISC")

ISC                               2014-04-18                       NSUPDATE(1)