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>nsupdate</TITLE
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><H1
><A
NAME="AEN1"
></A
>nsupdate</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8"
></A
><H2
>Name</H2
>nsupdate -- Dynamic DNS update utility</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN11"
></A
><H2
>Synopsis</H2
><P
><B
CLASS="COMMAND"
>nsupdate</B
> [<VAR
CLASS="OPTION"
>-d</VAR
>] [<VAR
CLASS="OPTION"
>-y <VAR
CLASS="REPLACEABLE"
>keyname:secret</VAR
></VAR
> | <VAR
CLASS="OPTION"
>-k <VAR
CLASS="REPLACEABLE"
>keyfile</VAR
></VAR
>] [<VAR
CLASS="OPTION"
>-t <VAR
CLASS="REPLACEABLE"
>timeout</VAR
></VAR
>] [<VAR
CLASS="OPTION"
>-u <VAR
CLASS="REPLACEABLE"
>udptimeout</VAR
></VAR
>] [<VAR
CLASS="OPTION"
>-r <VAR
CLASS="REPLACEABLE"
>udpretries</VAR
></VAR
>] [<VAR
CLASS="OPTION"
>-v</VAR
>] [filename]</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN35"
></A
><H2
>DESCRIPTION</H2
><P
><B
CLASS="COMMAND"
>nsupdate</B
>
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.</P
><P
>Zones that are under dynamic control via
<B
CLASS="COMMAND"
>nsupdate</B
>
or a DHCP server should not be edited by hand.
Manual edits could
conflict with dynamic updates and cause data to be lost.</P
><P
>The resource records that are dynamically added or removed with
<B
CLASS="COMMAND"
>nsupdate</B
>
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.</P
><P
>The
<VAR
CLASS="OPTION"
>-d</VAR
>
option makes
<B
CLASS="COMMAND"
>nsupdate</B
>
operate in debug mode.
This provides tracing information about the update requests that are
made and the replies received from the name server.</P
><P
>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
<B
CLASS="COMMAND"
>nsupdate</B
> 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
<SPAN
CLASS="TYPE"
>key</SPAN
>
and
<SPAN
CLASS="TYPE"
>server</SPAN
>
statements would be added to
<TT
CLASS="FILENAME"
>/etc/named.conf</TT
>
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.
<B
CLASS="COMMAND"
>nsupdate</B
>
does not read
<TT
CLASS="FILENAME"
>/etc/named.conf</TT
>.</P
><P
><B
CLASS="COMMAND"
>nsupdate</B
>
uses the
<VAR
CLASS="OPTION"
>-y</VAR
>
or
<VAR
CLASS="OPTION"
>-k</VAR
>
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
<VAR
CLASS="OPTION"
>-k</VAR
>
option,
<B
CLASS="COMMAND"
>nsupdate</B
>
reads the shared secret from the file
<VAR
CLASS="PARAMETER"
>keyfile</VAR
>,
whose name is of the form
<TT
CLASS="FILENAME"
>K{name}.+157.+{random}.private</TT
>.
For historical
reasons, the file
<TT
CLASS="FILENAME"
>K{name}.+157.+{random}.key</TT
>
must also be present. When the
<VAR
CLASS="OPTION"
>-y</VAR
>
option is used, a signature is generated from
<VAR
CLASS="PARAMETER"
>keyname:secret.</VAR
>
<VAR
CLASS="PARAMETER"
>keyname</VAR
>
is the name of the key,
and
<VAR
CLASS="PARAMETER"
>secret</VAR
>
is the base64 encoded shared secret.
Use of the
<VAR
CLASS="OPTION"
>-y</VAR
>
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
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>ps</SPAN
>(1)</SPAN
>
or in a history file maintained by the user's shell.</P
><P
>The <VAR
CLASS="OPTION"
>-k</VAR
> 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.</P
><P
>By default
<B
CLASS="COMMAND"
>nsupdate</B
>
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
<VAR
CLASS="OPTION"
>-v</VAR
>
option makes
<B
CLASS="COMMAND"
>nsupdate</B
>
use a TCP connection.
This may be preferable when a batch of update requests is made.</P
><P
>The <VAR
CLASS="OPTION"
>-t</VAR
> option sets the maximum time a update request can
take before it is aborted. The default is 300 seconds. Zero can be used
to disable the timeout.</P
><P
>The <VAR
CLASS="OPTION"
>-u</VAR
> 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.</P
><P
>The <VAR
CLASS="OPTION"
>-r</VAR
> option sets the number of UDP retries. The default is
3. If zero only one update request will be made.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN82"
></A
><H2
>INPUT FORMAT</H2
><P
><B
CLASS="COMMAND"
>nsupdate</B
>
reads input from
<VAR
CLASS="PARAMETER"
>filename</VAR
>
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.</P
><P
>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 <B
CLASS="COMMAND"
>send</B
> command) causes the
accumulated commands to be sent as one Dynamic DNS update request to the
name server.</P
><P
>The command formats and their meaning are as follows:
<P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><P
><B
CLASS="COMMAND"
>server</B
> {servername} [port]</P
></DT
><DD
><P
>Sends all dynamic update requests to the name server
<VAR
CLASS="PARAMETER"
>servername</VAR
>.
When no server statement is provided,
<B
CLASS="COMMAND"
>nsupdate</B
>
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.
<VAR
CLASS="PARAMETER"
>port</VAR
>
is the port number on
<VAR
CLASS="PARAMETER"
>servername</VAR
>
where the dynamic update requests get sent.
If no port number is specified, the default DNS port number of 53 is
used.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>local</B
> {address} [port]</P
></DT
><DD
><P
>Sends all dynamic update requests using the local
<VAR
CLASS="PARAMETER"
>address</VAR
>.
When no local statement is provided,
<B
CLASS="COMMAND"
>nsupdate</B
>
will send updates using an address and port chosen by the system.
<VAR
CLASS="PARAMETER"
>port</VAR
>
can additionally be used to make requests come from a specific port.
If no port number is specified, the system will assign one. </P
></DD
><DT
><P
><B
CLASS="COMMAND"
>zone</B
> {zonename}</P
></DT
><DD
><P
>Specifies that all updates are to be made to the zone
<VAR
CLASS="PARAMETER"
>zonename</VAR
>.
If no
<VAR
CLASS="PARAMETER"
>zone</VAR
>
statement is provided,
<B
CLASS="COMMAND"
>nsupdate</B
>
will attempt determine the correct zone to update based on the rest of the input.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>class</B
> {classname}</P
></DT
><DD
><P
>Specify the default class.
If no <VAR
CLASS="PARAMETER"
>class</VAR
> is specified the default class is
<VAR
CLASS="PARAMETER"
>IN</VAR
>.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>key</B
> {name} {secret}</P
></DT
><DD
><P
>Specifies that all updates are to be TSIG signed using the
<VAR
CLASS="PARAMETER"
>keyname</VAR
> <VAR
CLASS="PARAMETER"
>keysecret</VAR
> pair.
The <B
CLASS="COMMAND"
>key</B
> command
overrides any key specified on the command line via
<VAR
CLASS="OPTION"
>-y</VAR
> or <VAR
CLASS="OPTION"
>-k</VAR
>.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>prereq nxdomain</B
> {domain-name}</P
></DT
><DD
><P
>Requires that no resource record of any type exists with name
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>prereq yxdomain</B
> {domain-name}</P
></DT
><DD
><P
>Requires that
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>
exists (has as at least one resource record, of any type).</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>prereq nxrrset</B
> {domain-name} [class] {type}</P
></DT
><DD
><P
>Requires that no resource record exists of the specified
<VAR
CLASS="PARAMETER"
>type</VAR
>,
<VAR
CLASS="PARAMETER"
>class</VAR
>
and
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>.
If
<VAR
CLASS="PARAMETER"
>class</VAR
>
is omitted, IN (internet) is assumed.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>prereq yxrrset</B
> {domain-name} [class] {type}</P
></DT
><DD
><P
>This requires that a resource record of the specified
<VAR
CLASS="PARAMETER"
>type</VAR
>,
<VAR
CLASS="PARAMETER"
>class</VAR
>
and
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>
must exist.
If
<VAR
CLASS="PARAMETER"
>class</VAR
>
is omitted, IN (internet) is assumed.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>prereq yxrrset</B
> {domain-name} [class] {type} {data...}</P
></DT
><DD
><P
>The
<VAR
CLASS="PARAMETER"
>data</VAR
>
from each set of prerequisites of this form
sharing a common
<VAR
CLASS="PARAMETER"
>type</VAR
>,
<VAR
CLASS="PARAMETER"
>class</VAR
>,
and
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>
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
<VAR
CLASS="PARAMETER"
>type</VAR
>,
<VAR
CLASS="PARAMETER"
>class</VAR
>,
and
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>.
The
<VAR
CLASS="PARAMETER"
>data</VAR
>
are written in the standard text representation of the resource record's
RDATA.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>update delete</B
> {domain-name} [ttl] [class] [type [data...]]</P
></DT
><DD
><P
>Deletes any resource records named
<VAR
CLASS="PARAMETER"
>domain-name</VAR
>.
If
<VAR
CLASS="PARAMETER"
>type</VAR
>
and
<VAR
CLASS="PARAMETER"
>data</VAR
>
is provided, only matching resource records will be removed.
The internet class is assumed if
<VAR
CLASS="PARAMETER"
>class</VAR
>
is not supplied. The
<VAR
CLASS="PARAMETER"
>ttl</VAR
>
is ignored, and is only allowed for compatibility.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>update add</B
> {domain-name} {ttl} [class] {type} {data...}</P
></DT
><DD
><P
>Adds a new resource record with the specified
<VAR
CLASS="PARAMETER"
>ttl</VAR
>,
<VAR
CLASS="PARAMETER"
>class</VAR
>
and
<VAR
CLASS="PARAMETER"
>data</VAR
>.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>show</B
> </P
></DT
><DD
><P
>Displays the current message, containing all of the prerequisites and
updates specified since the last send.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>send</B
> </P
></DT
><DD
><P
>Sends the current message. This is equivalent to entering a blank line.</P
></DD
><DT
><P
><B
CLASS="COMMAND"
>answer</B
> </P
></DT
><DD
><P
>Displays the answer.</P
></DD
></DL
></DIV
> </P
><P
>Lines beginning with a semicolon are comments and are ignored.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN255"
></A
><H2
>EXAMPLES</H2
><P
>The examples below show how
<B
CLASS="COMMAND"
>nsupdate</B
>
could be used to insert and delete resource records from the
<SPAN
CLASS="TYPE"
>example.com</SPAN
>
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
<SPAN
CLASS="TYPE"
>example.com</SPAN
>.
<PRE
CLASS="PROGRAMLISTING"
># nsupdate
> update delete oldhost.example.com A
> update add newhost.example.com 86400 A 172.16.1.1
> send</PRE
></P
><P
>Any A records for
<SPAN
CLASS="TYPE"
>oldhost.example.com</SPAN
>
are deleted.
and an A record for
<SPAN
CLASS="TYPE"
>newhost.example.com</SPAN
>
it IP address 172.16.1.1 is added.
The newly-added record has a 1 day TTL (86400 seconds)
<PRE
CLASS="PROGRAMLISTING"
># nsupdate
> prereq nxdomain nickname.example.com
> update add nickname.example.com 86400 CNAME somehost.example.com
> send</PRE
></P
><P
>The prerequisite condition gets the name server to check that there
are no resource records of any type for
<SPAN
CLASS="TYPE"
>nickname.example.com</SPAN
>.
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.)</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN268"
></A
><H2
>FILES</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><CODE
CLASS="CONSTANT"
>/etc/resolv.conf</CODE
></DT
><DD
><P
>used to identify default name server</P
></DD
><DT
><CODE
CLASS="CONSTANT"
>K{name}.+157.+{random}.key</CODE
></DT
><DD
><P
>base-64 encoding of HMAC-MD5 key created by
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>dnssec-keygen</SPAN
>(8)</SPAN
>.</P
></DD
><DT
><CODE
CLASS="CONSTANT"
>K{name}.+157.+{random}.private</CODE
></DT
><DD
><P
>base-64 encoding of HMAC-MD5 key created by
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>dnssec-keygen</SPAN
>(8)</SPAN
>.</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN292"
></A
><H2
>SEE ALSO</H2
><P
><SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC2136</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC3007</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC2104</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC2845</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC1034</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC2535</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>RFC2931</SPAN
></SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>named</SPAN
>(8)</SPAN
>,
<SPAN
CLASS="CITEREFENTRY"
><SPAN
CLASS="REFENTRYTITLE"
>dnssec-keygen</SPAN
>(8)</SPAN
>. </P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN315"
></A
><H2
>BUGS</H2
><P
>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.</P
></DIV
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