nsupdate [-d] [-y keyname:secret | -k keyfile] [-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 up­
     date 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 trac­
     ing 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 up­
     dates.  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 appro­
     priate secret key and algorithm with the IP address of the client appli­
     cation 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 com­
     mand 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.

     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 prefer­
     able when a batch of update requests is made.


INPUT FORMAT

     nsupdate reads input from filename or standard input.  Each command is
     supplied on exactly one line of input.  Some commands are for administra­
     tive 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
     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 re­
     quests 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.

     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 giv­
     en type, class, and domain-name. The data are written in the standard
     text representation of the resource record's RDATA.

     update delete domain-name [class] [type [data...]]

     Deletes any resource records named domain-name. If type and data is pro­
     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
           >

     Any A records for oldhost.example.com are deleted.  and an A record for
     newhost.example.com it 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 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

     /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,  RFC2137,  RFC2104,  RFC2845,  RFC1034,  RFC2535,  named(8),
     dnssec-keygen(8).


BUGS

     The TSIG key is redundantly stored in two separate files.  This is a con­
     sequence of nsupdate using the DST library for its cryptographic opera­
     tions, and may change in future releases.

 BIND9                           Jun 30, 2000                                3

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