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NSUPDATE(1) BIND9 NSUPDATE(1)
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 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 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 user's 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 an 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:
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.
key {name} {secret}
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.
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 delete {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.
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 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 (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
Copyright (C) 2000-2003 Internet Software Consortium.
BIND9 Jun 30, 2000 NSUPDATE(1)
Generated by $Id: phpMan.php,v 4.54 2007/08/21 09:05:22 chedong Exp $ Author: Che Dong
On Apache/2.2.3 (CentOS)
Under GNU General Public License
2012-05-19 11:35 @172.29.30.74 CrawledBy CCBot/1.0 (+http://www.commoncrawl.org/bot.html)