nsupdate - dynamic DNS update utility
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]
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 must be in the same zone. Requests are sent to the zone's
    primary server, which 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, 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 are 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 is using TSIG authentication.
    ddns-confgen can 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.
  - -4
- This option sets use of IPv4 only.
 
  - -6
- This option sets use of IPv6 only.
 
  - -C
- Overrides the default resolv.conf file. This is only intended for
      testing.
 
  - -d
- This option sets debug mode, which provides tracing information about the
      update requests that are made and the replies received from the name
      server.
 
  - -D
- This option sets extra debug mode.
 
  - -g
- This option enables standard GSS-TSIG mode.
 
  - -i
- This option forces interactive mode, even when standard input is not a
      terminal.
 
  - -k keyfile
- This option indicates 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 option can 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
- This option sets local-host only mode, which sets the server address to
      localhost (disabling the server so that the server address cannot
      be overridden). Connections to the local server use a TSIG key found in
      @runstatedir@/session.key, which is automatically generated by
      named if any local primary zone has set update-policy
      to local. The location of this key file can be overridden with the
      -k option.
 
  - -L level
- This option sets the logging debug level. If zero, logging is
    disabled.
 
  - -o
- This option enables a non-standards-compliant variant of GSS-TSIG used by
      Windows 2000.
 
  - -p port
- This option sets the port to use for connections to a name server. The
      default is 53.
 
  - -P
- This option prints the list of private BIND-specific resource record types
      whose format is understood by nsupdate. See also the -T
      option.
 
  - -r udpretries
- This option sets the number of UDP retries. The default is 3. If zero,
      only one update request is made.
 
  - -t timeout
- This option sets the maximum time an update request can take before it is
      aborted. The default is 300 seconds. If zero, the timeout is disabled for
      TCP mode. For UDP mode, the option -u takes precedence over this
      option, unless the option -u is set to zero, in which case the
      interval is computed from the -t timeout interval and the number of
      UDP retries. For UDP mode, the timeout can not be disabled, and will be
      rounded up to 1 second in case if both -t and -u are set to
      zero.
 
  - -T
- This option prints the list of IANA standard resource record types whose
      format is understood by nsupdate. nsupdate exits 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, is parsed using the UNKNOWN rdata format,
        (<backslash> <hash> <space> <length>
        <space> <hexstring>). 
 
  - -u udptimeout
- This option sets the UDP retry interval. The default is 3 seconds. If
      zero, the interval is computed from the timeout interval and number of UDP
      retries.
 
  - -v
- This option specifies that TCP should be used 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 is used. TCP may be preferable when a batch of update
      requests is made.
 
  - -V
- This option prints the version number and exits.
 
  - -y [hmac:]keyname:secret
- This option sets the 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 ps1 or in a history file maintained by
        the user's shell. 
 
nsupdate reads input from filename or standard input. Each command
  is supplied on exactly one line of input. Some commands are for administrative
  purposes; 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 are
  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 either 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 meanings are as follows:
  - server servername port
- This command sends all dynamic update requests to the name server
      servername. When no server statement is provided, nsupdate
      sends updates to the primary server of the correct zone. The MNAME field
      of that zone's SOA record identify the primary server for that zone.
      port is the port number on servername where the dynamic
      update requests are sent. If no port number is specified, the default DNS
      port number of 53 is used.
    NOTE: 
This command has no effect when GSS-TSIG is in use.
 
  - local address port
- This command sends all dynamic update requests using the local
      address. When no local statement is provided, nsupdate sends
      updates using an address and port chosen by the system. port can
      also be used to force requests to come from a specific port. If no port
      number is specified, the system assigns one.
- zone zonename
- This command specifies that all updates are to be made to the zone
      zonename. If no zone statement is provided, nsupdate
      attempts to determine the correct zone to update based on the rest of the
      input.
- class classname
- This command specifies the default class. If no class is specified,
      the default class is IN.
- ttl seconds
- This command specifies the default time-to-live, in seconds, for records
      to be added. The value none clears the default TTL.
- key hmac:keyname secret
- This command specifies that all updates are to be TSIG-signed using the
      keyname-secret pair. If hmac is specified, it sets
      the signing algorithm in use. The default is hmac-md5; if MD5 was
      disabled, the default is hmac-sha256. The key command
      overrides any key specified on the command line via -y or
      -k.
- gsstsig
- This command uses GSS-TSIG to sign the updates. This is equivalent to
      specifying -g on the command line.
- oldgsstsig
- This command uses the Windows 2000 version of GSS-TSIG to sign the
      updates. This is equivalent to specifying -o on the command
    line.
- realm [realm_name]
- When using GSS-TSIG, this command specifies the use of realm_name
      rather than the default realm in krb5.conf. If no realm is
      specified, the saved realm is cleared.
- check-names [boolean]
- This command turns 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 is not added to the UPDATE message.
- prereq nxdomain domain-name
- This command requires that no resource record of any type exist with the
      name domain-name.
- prereq yxdomain domain-name
- This command requires that domain-name exist (as at least one
      resource record, of any type).
- prereq nxrrset domain-name class type
- This command requires that no resource record exist of the specified
      type, class, and domain-name. If class is
      omitted, IN (Internet) is assumed.
- prereq yxrrset domain-name class type
- This command requires that a resource record of the specified type,
      class and domain-name exist. If class is omitted, IN
      (internet) is assumed.
- prereq yxrrset domain-name class type data
- With this command, 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
- This command deletes any resource records named domain-name. If
      type and data are provided, only matching resource records
      are 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
- This command adds a new resource record with the specified ttl,
      class, and data.
- show
- This command displays the current message, containing all of the
      prerequisites and updates specified since the last send.
- send
- This command sends the current message. This is equivalent to entering a
      blank line.
- answer
- This command displays the answer.
- debug
- This command turns on debugging.
- version
- This command prints the version number.
- help
- This command prints a list of commands.
 
Lines beginning with a semicolon (;) are comments and are
  ignored.
The examples below show how nsupdate can 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 is
  sent as one dynamic update request to the primary 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 TTL of 1 day (86400 seconds).
# nsupdate
> prereq nxdomain nickname.example.com
> update add nickname.example.com 86400 CNAME somehost.example.com
> send
 
 
The prerequisite condition tells the name server to verify 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.)
  - /etc/resolv.conf
- Used to identify the default name server
- @runstatedir@/session.key
- Sets the default TSIG key for use in local-only mode
- K{name}.+157.+{random}.key
- Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
- K{name}.+157.+{random}.private
- Base-64 encoding of the HMAC-MD5 key created by dnssec-keygen.
 
RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC
  1034, RFC 2535, RFC 2931, named(8),
  dnssec-keygen(8), tsig-keygen(8).
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.
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