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NSUPDATE(8) NSUPDATE(8)
NAME
nsupdate - Dynamic DNS update utility
SYNOPSIS
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
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 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. 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 appropriate secret key and algorithm with the
IP address of the client application that will be using TSIG authenti-
cation. 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 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.
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 preferable 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 adminis-
trative purposes. The others are either update instructions or pre-
requisite 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 server-
name. 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 speci-
fied, 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 addi-
tionally 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 deter-
mine 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 key-
name keysecret pair. The key command overrides any key speci-
fied 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 sup-
plied. The ttl is ignored, and is only allowed for compatibil-
ity.
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 prerequi-
sites and updates specified since the last send.
send Sends the current message. This is equivalent to entering a
blank line.
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
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, RFC3007, RFC2104, RFC2845, RFC1034, RFC2535, 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.
BIND9 Jun 30, 2000 NSUPDATE(8)
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