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nsupdate(1)                         BIND 9                         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 nsup-
       date 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 gener-
       ate 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     This option sets use of IPv4 only.

       -6     This option sets use of IPv6 only.

       -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.

       -i     This option forces interactive mode, even when standard input is
              not a terminal.

       -k keyfile
              This  option  indicates the file containing the TSIG authentica-
              tion key. Keyfiles may be in two formats: a single file contain-
              ing  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  /var/run/named/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.

       -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.

       -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  sec-
              onds.  If zero, the interval is computed from the timeout inter-
              val 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.


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; 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  pre-
       requisite 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 miss-
       ing 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, nsup-
              date 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.

       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 speci-
              fied, 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 equiva-
              lent 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 [yes_or_no]
              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 spec-
              ified  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 com-
              bined 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  rep-
              resentation 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 sup-
              plied. The ttl is ignored, and is only allowed  for  compatibil-
              ity.

       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.


EXAMPLES

       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  com-
       mands  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 con-
       flict 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 the 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 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.


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


COPYRIGHT

       2021, Internet Systems Consortium



9.16.12                           2021-02-04                       nsupdate(1)

bind 9.16.12 - Generated Sat Feb 20 08:42:11 CST 2021
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