NSUPDATE(8) BIND9 NSUPDATE(8)
NAME
nsupdate - Dynamic DNS update utility
SYNOPSIS
nsupdate [-d] [[-y keyname:secret] | [-k keyfile]] [-t timeout]
[-u udptimeout] [-r udpretries] [-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 zones
master server. This is identified by the MNAME field of the zones 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 (with an HMAC-MD5 key) 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 command line argument in
clear text. This may be visible in the output from ps(1 ) or in a
history file maintained by the users 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 a 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.
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:
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 zones 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.
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.
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.
Specify the default class. If no
class is specified the default class is IN.
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.
Requires that no resource record of any type exists with name
domain-name.
Requires that
domain-name exists (has as at least one resource
record, of any type).
Requires that no resource record exists of the specified
type, class and domain-name. If class is omitted, IN
(internet) is assumed.
This requires that a resource record of the specified
type, class and domain-name must exist. If class is
omitted, IN (internet) is assumed.
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 records
RDATA.
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.
Adds a new resource record with the specified
ttl, class and data.
Displays the current message, containing all of the
prerequisites and updates specified since the last send.
Sends the current message. This is equivalent to entering a
blank line.
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 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 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 2004, 2005 Internet Systems Consortium, Inc. ("ISC")
BIND9 Jun 30, 2000 NSUPDATE(8)
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