NSUPDATE(1) BIND9 NSUPDATE(1)
NAME
nsupdate - Dynamic DNS update utility
SYNOPSIS
nsupdate [-d] [-D] [-i] [-L level] [[-g] | [-o] | [-l] |
[-y [hmac:]keyname:secret] | [-k keyfile]] [-t timeout]
[-u udptimeout] [-r udpretries] [-R randomdev] [-v] [-T] [-P]
[-V] [filename]
DESCRIPTION
nsupdate is used to submit Dynamic DNS Update requests as defined in
RFC 2136 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.
Transaction signatures can be used to authenticate the Dynamic DNS
updates. These use the TSIG resource record type described in RFC 2845
or the SIG(0) record described in RFC 2535 and RFC 2931 or GSS-TSIG as
described in RFC 3645.
TSIG relies on a shared secret that should only be known to nsupdate
and the name server. 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. You can use
ddns-confgen to generate suitable configuration fragments. nsupdate
uses the -y or -k options to provide the TSIG shared secret. These
options are mutually exclusive.
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.
GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode is switched
on with the -g flag. A non-standards-compliant variant of GSS-TSIG used
by Windows 2000 can be switched on with the -o flag.
OPTIONS
-d
Debug mode. This provides tracing information about the update
requests that are made and the replies received from the name
server.
-D
Extra debug mode.
-i
Force interactive mode, even when standard input is not a terminal.
-k keyfile
The file containing the TSIG authentication key. Keyfiles may be in
two formats: a single file containing a named.conf-format key
statement, which may be generated automatically by ddns-confgen, or
a pair of files whose names are of the format
K{name}.+157.+{random}.key and K{name}.+157.+{random}.private,
which can be generated by dnssec-keygen. 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.
-l
Local-host only mode. This sets the server address to localhost
(disabling the server so that the server address cannot be
overridden). Connections to the local server will use a TSIG key
found in /var/run/named/session.key, which is automatically
generated by named if any local master zone has set update-policy
to local. The location of this key file can be overridden with the
-k option.
-L level
Set the logging debug level. If zero, logging is disabled.
-p port
Set the port to use for connections to a name server. The default
is 53.
-P
Print the list of private BIND-specific resource record types whose
format is understood by nsupdate. See also the -T option.
-r udpretries
The number of UDP retries. The default is 3. If zero, only one
update request will be made.
-R randomdev
Where to obtain randomness. If the operating system does not
provide a /dev/random or equivalent device, the default source of
randomness is keyboard input. randomdev specifies the name of a
character device or file containing random data to be used instead
of the default. The special value keyboard indicates that keyboard
input should be used. This option may be specified multiple times.
-t timeout
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.
-T
Print the list of IANA standard resource record types whose format
is understood by nsupdate. nsupdate will exit after the lists are
printed. The -T option can be combined with the -P option.
Other types can be entered using "TYPEXXXXX" where "XXXXX" is the
decimal value of the type with no leading zeros. The rdata, if
present, will be parsed using the UNKNOWN rdata format,
(<backslash> <hash> <space> <length> <space> <hexstring>).
-u udptimeout
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.
-v
Use TCP even for small update requests. 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. TCP
may be preferable when a batch of update requests is made.
-V
Print the version number and exit.
-y [hmac:]keyname:secret
Literal TSIG authentication key. keyname is the name of the key,
and secret is the base64 encoded shared secret. hmac is the name
of the key algorithm; valid choices are hmac-md5, hmac-sha1,
hmac-sha224, hmac-sha256, hmac-sha384, or hmac-sha512. If hmac is
not specified, the default is hmac-md5 or if MD5 was disabled
hmac-sha256.
NOTE: 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.
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.
ttl {seconds}
Specify the default time to live for records to be added. The value
none will clear the default ttl.
key [hmac:] {keyname} {secret}
Specifies that all updates are to be TSIG-signed using the keyname
secret pair. If hmac is specified, then it sets the signing
algorithm in use; the default is hmac-md5 or if MD5 was disabled
hmac-sha256. The key command overrides any key specified on the
command line via -y or -k.
gsstsig
Use GSS-TSIG to sign the updated. This is equivalent to specifying
-g on the command line.
oldgsstsig
Use the Windows 2000 version of GSS-TSIG to sign the updated. This
is equivalent to specifying -o on the command line.
realm {[realm_name]}
When using GSS-TSIG use realm_name rather than the default realm in
krb5.conf. If no realm is specified the saved realm is cleared.
check-names {[yes_or_no]}
Turn on or off check-names processing on records to be added.
Check-names has no effect on prerequisites or records to be
deleted. By default check-names processing is on. If check-names
processing fails the record will not be added to the UPDATE
message.
[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] del[ete] {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.
debug
Turn on debugging.
version
Print version number.
help
Print a list of commands.
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 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 RRSIG, DNSKEY
and NSEC records.)
FILES
/etc/resolv.conf
used to identify default name server
/var/run/named/session.key
sets the default TSIG key for use in local-only mode
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
RFC 2136, RFC 3007, RFC 2104, RFC 2845, RFC 1034, RFC 2535, RFC 2931,
named(8), ddns-confgen(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.
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright (C) 2000-2012, 2014-2021 Internet Systems Consortium, Inc.
("ISC")
ISC 2014-04-18 NSUPDATE(1)
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