<section xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="dyndb-info"><info><title>DynDB (Dynamic Database)</title></info>

<para>

DynDB is an extension to BIND 9 which, like DLZ

(see <xref linkend="dlz-info"/>), allows zone data to be

retrieved from an external database. Unlike DLZ, a DynDB module

provides a full-featured BIND zone database interface. Where

DLZ translates DNS queries into real-time database lookups,

resulting in relatively poor query performance, and is unable

to handle DNSSEC-signed data due to its limited API, a DynDB

module can pre-load an in-memory database from the external

data source, providing the same performance and functionality

as zones served natively by BIND.

</para>

<para>

A DynDB module supporting LDAP has been created by Red Hat

and is available from

<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://fedorahosted.org/bind-dyndb-ldap/">https://fedorahosted.org/bind-dyndb-ldap/</link>.

</para>

<para>

A sample DynDB module for testing and developer guidance

is included with the BIND source code, in the directory

<filename>bin/tests/system/dyndb/driver</filename>.

</para>

<section><info><title>Configuring DynDB</title></info>

<para>

A DynDB database is configured with a <command>dyndb</command>

statement in <filename>named.conf</filename>:

</para>

<screen>

dyndb example "driver.so" {

<replaceable>parameters</replaceable>

};

</screen>

<para>

The file <filename>driver.so</filename> is a DynDB module which

implements the full DNS database API. Multiple

<command>dyndb</command> statements can be specified, to load

different drivers or multiple instances of the same driver.

Zones provided by a DynDB module are added to the view's zone

table, and are treated as normal authoritative zones when BIND

is responding to queries. Zone configuration is handled internally

by the DynDB module.

</para>

<para>

The <replaceable>parameters</replaceable> are passed as an opaque

string to the DynDB module's initialization routine. Configuration

syntax will differ depending on the driver.

</para>

</section>

<section><info><title>Sample DynDB Module</title></info>

<para>

For guidance in implementation of DynDB modules, the directory

<filename>bin/tests/system/dyndb/driver</filename>.

contains a basic DynDB module.

The example sets up two zones, whose names are passed

to the module as arguments in the <command>dyndb</command>

statement:

</para>

<screen>

dyndb sample "sample.so" { example.nil. arpa. };

</screen>

<para>

In the above example, the module is configured to create a zone

"example.nil", which can answer queries and AXFR requests, and

accept DDNS updates. At runtime, prior to any updates, the zone

contains an SOA, NS, and a single A record at the apex:

</para>

<screen>

example.nil. 86400 IN SOA example.nil. example.nil. (

0 28800 7200 604800 86400

)

example.nil. 86400 IN NS example.nil.

example.nil. 86400 IN A 127.0.0.1

</screen>

<para>

When the zone is updated dynamically, the DynDB module will determine

whether the updated RR is an address (i.e., type A or AAAA) and if

so, it will automatically update the corresponding PTR record in a

reverse zone. (Updates are not stored permanently; all updates are

lost when the server is restarted.)

</para>

</section>

</section>