nsupdate(1M) System Administration Commands nsupdate(1M)
NAME
nsupdate - Dynamic DNS update utility
SYNOPSIS
nsupdate [-dv] [-y keyname:secret | -k keyfile] [filename]
DESCRIPTION
The nsupdate utility submits Dynamic DNS Update requests as defined in RFC 2136 to a name server. This utility 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 with 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 must be in the same zone. Requests are sent to the zone's master
servers identified by the MNAME field of the zone's SOA record.
Transaction signatures can be used to authenticate the Dynamic DNS updates using the TSIG resource record type described in RFC 2845. 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
that they select the appropriate algorithm as well as the key when authenticating each other. For instance, suitable key and server state-
ments 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. The nsupdate utility does not read /etc/named.conf.
The nsupdate utility 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. See OPTIONS.
OPTIONS
The following options are supported:
-d Operate in debug mode. This provides tracing information about the update requests that are made and the replies
received from the name server.
-k keyfile Read the shared secret from the file keyfile, whose name is of the form K{name}.+157.+{random}.private. For his-
torical reasons, the file K{name}.+157.+{random}.key must also be present.
-v Use a TCP connection. Using a TCP connection could be preferable when a batch of update requests is made. By
default, nsupdate uses UDP to send update requests to the name server.
-y keyname:secret Generate a signature from keyname:secret, wherekeyname 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
and could be visible in the output from ps(1) or in a history file maintained by the user's shell.
INPUT FORMAT
The nsupdate utility reads input from filename or the 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 condition 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 ]
Send all dynamic update requests to the name server servername. When no server statement is provided, nsupdate sends updates to the
master server of the correct zone. The MNAME field of that zone's SOA record identifies the master server for that zone. The port argu-
ment 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 ]
Send 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. The port argument can also be used to make requests come from a specific port. If no port number is
specified, the system assigns one.
zone zonename
Specify that all updates are to be made to the zone zonename. If no zone statement is provided, nsupdate attempts to determine the cor-
rect 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
Specify that all updates are to be TSIG signed using the name secret pair. The key command overrides any key specified on the command
line with -y or -k.
prereq nxdomain domain-name
Require that no resource record of any type exists withthe name domain-name.
prereq yxdomain domain-name
Require that domain-name exists (has as at least one resource record, of any type).
prereq nxrrset domain-name [ class ] type
Require 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
Require 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... ] ]
Delete 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 supplied. The ttl is ignored, and is only provided for compatibility.
update add domain-name ttl [ class ] type data...
Add a new resource record with the specified ttl, class and data.
show
Display the current message, containing all of the prerequisites and updates specified since the last send.
send
Sens the current message. This is equivalent to entering a blank line.
Lines beginning with a semicolon are comments and are ignored.
EXAMPLES
Example 1: Insert and delete resource records from the zone.
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. 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 action ensures that when the CNAME is added, it
cannot conflict 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 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(1M).
K{name}.+157.+{random}.private base-64 encoding of HMAC-MD5 key created by dnssec-keygen(1M)
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 could change in future releases.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|Availability |SUNWbind9 |
|Interface Stability |External |
+-----------------------------+-----------------------------+
SEE ALSO
named(1M), dnssec-keygen(1M), attributes(5)
RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535
NOTES
Source for BIND9 is available in the SUNWbind9S package.
SunOS 5.10 15 Dec 2004 nsupdate(1M)