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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>3. Master operation</title><link rel="stylesheet" href="docbook.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="PowerDNS manual" /><link rel="up" href="replication.html" title="Chapter 18. Master/Slave operation & replication" /><link rel="prev" href="slave.html" title="2. Slave operation" /><link rel="next" href="fancy-records.html" title="Chapter 19. Fancy records for seamless email and URL integration" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">3. Master operation</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="slave.html">Prev</a> </td><th width="60%" align="center">Chapter 18. Master/Slave operation & replication</th><td width="20%" align="right"> <a accesskey="n" href="fancy-records.html">Next</a></td></tr></table><hr /></div><div class="sect1" title="3. Master operation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="master"></a>3. Master operation</h2></div></div></div><p>
When operating as a master, PDNS sends out notifications of changes to slaves, which react to these notifications by querying PDNS to see
if the zone changed, and transferring its contents if it has. Notifications are a way to promptly propagate zone changes to slaves, as
described in RFC 1996.
</p><p>
</p><div class="warning" title="Warning" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Warning"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="warning.png" /></td><th align="left">Warning</th></tr><tr><td align="left" valign="top"><p>
Master support is OFF by default, turn it on by adding <span class="command"><strong>master</strong></span> to the configuration. The same
holds for slave operation. Both can be on simultaneously.
</p></td></tr></table></div><p>
</p><div class="warning" title="Warning" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Warning"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="warning.png" /></td><th align="left">Warning</th></tr><tr><td align="left" valign="top"><p>
If you have DNSSEC-signed zones and non-PowerDNS slaves, please check your SOA-EDIT settings.
</p></td></tr></table></div><p>
</p><p>
Left open by RFC 1996 is who is to be notified - which is harder to figure out than it sounds. All slaves for this domain must receive a notification
but the nameserver only knows the names of the slaves - not the IP addresses, which is where the problem lies. The nameserver itself might
be authoritative for the name of its secondary, but not have the data available.
</p><p>
To resolve this issue, PDNS tries multiple tactics to figure out the IP addresses of the slaves, and notifies everybody. In contrived configurations
this may lead to duplicate notifications being sent out, which shouldn't hurt.
</p><p>
Some backends may be able to detect zone changes, others may chose to let the operator indicate which zones have changed and which haven't.
Consult the documentation for your backend to see how it processes changes in zones.
</p><p>
To help deal with slaves that may have missed notifications, or have failed to respond to them, several override commands are available via
the pdns_control tool (<a class="xref" href="pdns-internals.html#pdnscontrol" title="1.1. pdns_control">Section 1.1, “pdns_control”</a>):
</p><p>
</p><div class="variablelist"><dl><dt><span class="term">pdns_control notify <span class="command"><strong>domain</strong></span></span></dt><dd><p>
This instructs PDNS to notify all IP addresses it considers to be slaves of this domain.
</p></dd><dt><span class="term">pdns_control notify-host <span class="command"><strong>domain ip-address</strong></span></span></dt><dd><p>
This is truly an override and sends a notification to an arbitrary IP address. Can be used in 'also-notify' situations
or when PDNS has trouble figuring out who to notify - which may happen in contrived configurations.
</p></dd></dl></div><p>
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="slave.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="replication.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="fancy-records.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2. Slave operation </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 19. Fancy records for seamless email and URL integration</td></tr></table></div></body></html>
