<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Master operation</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="PowerDNS manual"
HREF="index.html"><LINK
REL="UP"
TITLE="Master/Slave operation & replication"
HREF="replication.html"><LINK
REL="PREVIOUS"
TITLE="Slave operation"
HREF="slave.html"><LINK
REL="NEXT"
TITLE="Fancy records for seamless email and URL integration"
HREF="fancy-records.html"></HEAD
><BODY
CLASS="SECT1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>PowerDNS manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="slave.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 13. Master/Slave operation & replication</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="fancy-records.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="MASTER"
>13.3. Master operation</A
></H1
><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
> <DIV
CLASS="WARNING"
><P
></P
><TABLE
CLASS="WARNING"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="../images/warning.gif"
HSPACE="5"
ALT="Warning"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
> Master support is OFF by default, turn it on by adding <B
CLASS="COMMAND"
>master</B
> to the configuration. The same
holds for slave operation. Both can be on simultaneously.
</P
></TD
></TR
></TABLE
></DIV
>
</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
HREF="pdns-internals.html#PDNSCONTROL"
>Section B.1.1</A
>):
</P
><P
> <P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>pdns_control notify <B
CLASS="COMMAND"
>domain</B
></DT
><DD
><P
> This instructs PDNS to notify all IP addresses it considers to be slaves of this domain.
</P
></DD
><DT
>pdns_control notify-host <B
CLASS="COMMAND"
>domain ip-address</B
></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
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="slave.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="fancy-records.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Slave operation</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="replication.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Fancy records for seamless email and URL integration</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
