NAME
nsupdate - Dynamic DNS update utility
SYNOPSIS
nsupdate
[ -d] [-D] [-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.
-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 keynamesecret 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 commandline.
oldgsstsig
Use the Windows 2000 version of GSS-TSIG to
sign the updated. This is equivalent to specifying -o on the
commandline.
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.
[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 © 2004-2012, 2014-2016 Internet Systems Consortium, Inc.
("ISC")
Copyright © 2000-2003 Internet Software Consortium.