a439ed326d59951678c2cb53a1962d862985ce70Tilo Mitra<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">

<refentry>

<refentryinfo>

<date>Jun 30, 2000</date>

</refentryinfo>

<refmeta>

<refentrytitle>nsupdate</refentrytitle>

<manvolnum>8</manvolnum>

<refmiscinfo>BIND9</refmiscinfo>

</refmeta>

<refnamediv>

<refname>nsupdate</refname>

<refpurpose>Dynamic DNS update utility</refpurpose>

</refnamediv>

<refsynopsisdiv>

<cmdsynopsis>

<command>nsupdate</command>

<arg><option>-d</option></arg>

<group>

<arg><option>-y <replaceable class="parameter">keyname:secret</replaceable></option></arg>

<arg><option>-k <replaceable class="parameter">keyfile</replaceable></option></arg>

</group>

<arg><option>-v</option></arg>

<arg>filename</arg>

</cmdsynopsis>

</refsynopsisdiv>

<refsect1>

<title>DESCRIPTION</title>

<para>

<command>nsupdate</command>

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.

</para>

<para>

Zones that are under dynamic control via

<command>nsupdate</command>

or a DHCP server should not be edited by hand.

Manual edits could

conflict with dynamic updates and cause data to be lost.

</para>

<para>

The resource records that are dynamically added or removed with

<command>nsupdate</command>

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.

</para>

<para>

The

<option>-d</option>

option makes

<command>nsupdate</command>

operate in debug mode.

This provides tracing information about the update requests that are

made and the replies received from the name server.

</para>

<para>

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

<command>nsupdate</command>

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

<type>key</type>

and

<type>server</type>

statements would be added to

<filename>/etc/named.conf</filename>

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.

<command>nsupdate</command>

does not read

<filename>/etc/named.conf</filename>.

</para>

<para>

<command>nsupdate</command>

uses the

<option>-y</option>

or

<option>-k</option>

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

<option>-k</option>

option,

<command>nsupdate</command>

reads the shared secret from the file

<parameter>keyfile</parameter>,

whose name is of the form

<filename>K{name}.+157.+{random}.private</filename>.

For historical

reasons, the file

<filename>K{name}.+157.+{random}.key</filename>

must also be present. When the

<option>-y</option>

option is used, a signature is generated from

<parameter>keyname:secret.</parameter>

<parameter>keyname</parameter>

is the name of the key,

and

<parameter>secret</parameter>

is the base64 encoded shared secret.

Use of the

<option>-y</option>

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

<citerefentry>

<refentrytitle>ps</refentrytitle><manvolnum>1

</manvolnum>

</citerefentry>

or in a history file maintained by the user's shell.

</para>

<para>

By default

<command>nsupdate</command>

uses UDP to send update requests to the name server.

The

<option>-v</option>

option makes

<command>nsupdate</command>

use a TCP connection.

This may be preferable when a batch of update requests is made.

</para>

</refsect1>

<refsect1>

<title>INPUT FORMAT</title>

<para>

<command>nsupdate</command>

reads input from

<parameter>filename</parameter>

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.

</para>

<para>

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 <command>send</command> command) causes the

accumulated commands to be sent as one Dynamic DNS update request to the

name server.

</para>

<para>

The command formats and their meaning are as follows:

<variablelist>

<varlistentry><term>

<cmdsynopsis>

<command>server</command>

<arg choice="req">servername</arg>

<arg choice="opt">port</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Sends all dynamic update requests to the name server

<parameter>servername</parameter>.

When no server statement is provided,

<command>nsupdate</command>

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.

<parameter>port</parameter>

is the port number on

<parameter>servername</parameter>

where the dynamic update requests get sent.

If no port number is specified, the default DNS port number of 53 is

used.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>local</command>

<arg choice="req">address</arg>

<arg choice="opt">port</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Sends all dynamic update requests using the local

<parameter>address</parameter>.

When no local statement is provided,

<command>nsupdate</command>

will send updates using an address and port choosen by the system.

<parameter>port</parameter>

can additionally be used to make requests come from a specific port.

If no port number is specified, the system will assign one.

<varlistentry><term>

<cmdsynopsis>

<command>zone</command>

<arg choice="req">zonename</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Specifies that all updates are to be made to the zone

<parameter>zonename</parameter>.

If no

<parameter>zone</parameter>

statement is provided,

<command>nsupdate</command>

will attempt determine the correct zone to update based on the rest of the input.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>key</command>

<arg choice="req">name</arg>

<arg choice="req">secret</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Specifies that all updates are to be TSIG signed using the

<parameter>keyname</parameter> <parameter>keysecret</parameter> pair.

The <command>key</command> command

overrides any key specified on the command line via

<option>-y</option> or <option>-k</option>.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>prereq nxdomain</command>

<arg choice="req">domain-name</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Requires that no resource record of any type exists with name

<parameter>domain-name</parameter>.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>prereq yxdomain</command>

<arg choice="req">domain-name</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Requires that

<parameter>domain-name</parameter>

exists (has as at least one resource record, of any type).

</para>

<varlistentry><term>

<cmdsynopsis>

<command>prereq nxrrset</command>

<arg choice="req">domain-name</arg>

<arg choice="opt">class</arg>

<arg choice="req">type</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Requires that no resource record exists of the specified

<parameter>type</parameter>,

<parameter>class</parameter>

and

<parameter>domain-name</parameter>.

If

<parameter>class</parameter>

is omitted, IN (internet) is assumed.

<varlistentry><term>

<cmdsynopsis>

<command>prereq yxrrset</command>

<arg choice="req">domain-name</arg>

<arg choice="opt">class</arg>

<arg choice="req">type</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

This requires that a resource record of the specified

<parameter>type</parameter>,

<parameter>class</parameter>

and

<parameter>domain-name</parameter>

must exist.

If

<parameter>class</parameter>

is omitted, IN (internet) is assumed.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>prereq yxrrset</command>

<arg choice="req">domain-name</arg>

<arg choice="opt">class</arg>

<arg choice="req">type</arg>

<arg choice="req" rep="repeat">data</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

The

<parameter>data</parameter>

from each set of prerequisites of this form

sharing a common

<parameter>type</parameter>,

<parameter>class</parameter>,

and

<parameter>domain-name</parameter>

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

<parameter>type</parameter>,

<parameter>class</parameter>,

and

<parameter>domain-name</parameter>.

The

<parameter>data</parameter>

are written in the standard text representation of the resource record's

RDATA.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>update delete</command>

<arg choice="req">domain-name</arg>

<arg choice="opt">ttl</arg>

<arg choice="opt">class</arg>

<arg choice="opt">type <arg choice="opt" rep="repeat">data</arg></arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Deletes any resource records named

<parameter>domain-name</parameter>.

If

<parameter>type</parameter>

and

<parameter>data</parameter>

is provided, only matching resource records will be removed.

The internet class is assumed if

<parameter>class</parameter>

is not supplied. The

<parameter>ttl</parameter>

is ignored, and is only allowed for compatibility.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>update add</command>

<arg choice="req">domain-name</arg>

<arg choice="req">ttl</arg>

<arg choice="opt">class</arg>

<arg choice="req">type</arg>

<arg choice="req" rep="repeat">data</arg>

</cmdsynopsis>

</term>

<listitem>

<para>

Adds a new resource record with the specified

<parameter>ttl</parameter>,

<parameter>class</parameter>

and

<parameter>data</parameter>.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>show</command>

</cmdsynopsis>

</term>

<listitem>

<para>

Displays the current message, containing all of the prerequisites and

updates specified since the last send.

</para>

<varlistentry><term>

<cmdsynopsis>

<command>send</command>

</cmdsynopsis>

</term>

<listitem>

<para>

Sends the current message. This is equivalent to entering a blank line.

</para>

</listitem>

</variablelist>

<para>

Lines beginning with a semicolon are comments, and are ignored.

</para>

</refsect1>

<refsect1>

<title>EXAMPLES</title>

<para>

The examples below show how

<command>nsupdate</command>

could be used to insert and delete resource records from the

<type>example.com</type>

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

<type>example.com</type>.

<programlisting>

# nsupdate

> update delete oldhost.example.com A

> update add newhost.example.com 86400 A 172.16.1.1

>

</programlisting>

</para>

<para>

Any A records for

<type>oldhost.example.com</type>

are deleted.

and an A record for

<type>newhost.example.com</type>

it IP address 172.16.1.1 is added.

The newly-added record has a 1 day TTL (86400 seconds)

<programlisting>

# nsupdate

> prereq nxdomain nickname.example.com

> update add nickname.example.com CNAME somehost.example.com

>

</programlisting>

</para>

<para>

The prerequisite condition gets the name server to check that there

are no resource records of any type for

<type>nickname.example.com</type>.

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.)

</para>

</refsect1>

<refsect1>

<title>FILES</title>

<variablelist>

<varlistentry><term><constant>/etc/resolv.conf</constant></term>

<listitem>

<para>

used to identify default name server

</para>

</listitem>

<varlistentry><term><constant>K{name}.+157.+{random}.key</constant></term>

<listitem>

<para>

base-64 encoding of HMAC-MD5 key created by

<citerefentry>

<refentrytitle>dnssec-keygen</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>.

</para>

</listitem>

<varlistentry><term><constant>K{name}.+157.+{random}.private</constant></term>

<listitem>

<para>

base-64 encoding of HMAC-MD5 key created by

<citerefentry>

<refentrytitle>dnssec-keygen</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>.

</para>

</listitem>

</variablelist>

</refsect1>

<refsect1>

<title>SEE ALSO</title>

<para>

<citerefentry>

<refentrytitle>RFC2136</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>RFC3007</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>RFC2104</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>RFC2845</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>RFC1034</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>RFC2535</refentrytitle>

</citerefentry>,

<citerefentry>

<refentrytitle>named</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>,

<citerefentry>

<refentrytitle>dnssec-keygen</refentrytitle><manvolnum>8</manvolnum>

</citerefentry>.

</refsect1>

<refsect1>

<title>BUGS</title>

<para>

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.

</para>

</refsect1>

</refentry>