                      Having MaraDNS be a slave DNS server

   MaraDNS does not have direct support for being a slave DNS server.
   However, MaraDNS can transfer zone files from other servers by using the
   fetchzone client.

   fetchzone is a program that can transfer a zone from another name server;
   the transferred zone is in the csv2 zone file format, which can then be
   loaded by MaraDNS.

   Here is an example of using fetchzone to transfer the zone example.com
   from the server with the IP 10.5.6.7, placing the output in the file
   "db.example.com":

 fetchzone example.com 10.5.6.7 > db.example.com

Automating this with a shell script

   If one wishes to use fetchzone to grab a number of zones, this can be
   automated with a shell script:

 #!/bin/bash

 cd /opt/local/etc/maradns
 fetchzone example.com 10.5.6.7 > db.example.com
 fetchzone example.org 192.168.5.67 > db.example.org
 fetchzone example.net 172.19.2.83 > db.example.net

   This shell script, however, has a problem. Should there be a problem
   getting a zone file from a remote system, the zone file in question will
   be destroyed. This can be avoided by checking the exit status of fetchzone
   in the shell script, making sure that the zone was obtained normally
   before overwriting the zone file:

 #!/bin/bash

 # For security reasons, put this file in a directory that only root
 # may write to. 
 TEMP=/root/tmp/foo

 cd /opt/local/etc/maradns
 fetchzone example.com 10.5.6.7 > $TEMP
 if [ $? -eq 0 ] ; then
         mv $TEMP db.example.com
 fi
 fetchzone example.org 192.168.5.67 > $TEMP
 if [ $? -eq 0 ] ; then
         mv $TEMP db.example.org
 fi
 fetchzone example.net 172.19.2.83 > $TEMP
 if [ $? -eq 0 ] ; then
         mv $TEMP db.example.net
 fi

   Note that this script needs a directory, which only root may write to,
   named /root/tmp (Linux has a long-standing tradition of making root's home
   directory /root; place this file elsewhere on a system with a different
   root directory).

   While this script is workable for a small number of zones, this script
   will quickly become unwieldy for a large number of zones. If one wants to
   grab a large number of zones, it makes more sense to have the list of
   zones in a separate file. We then have the shell script read this file
   (list of zones and IPs), and make the zone files live if the zones have
   been successfully fetched.

   Here is what a shell script may look like:

 #!/bin/bash

 ZONELIST=/opt/local/etc/maradns.zonelist
 # For security reasons, put this file in a directory that only root
 # may write to. 
 TEMP=/root/tmp/foo

 cd /opt/local/etc/maradns

 cat $ZONELIST | awk '{print "fetchzone "$1" "$2" > '$TEMP'"
                       print "if [ $? -eq 0 ] ; then"
                       print "    mv '$TEMP' db."$1
                       print "fi";}' | sh

   The list of zones, which is in the file /opt/local/etc/maradns.zonelist in the above
   example, will look like this:

 example.com 10.5.6.7
 example.org 192.168.5.67
 example.net 172.19.2.83

   Note that the presence of a given db.name file in the /opt/local/etc/maradns
   directory is not sufficient for MaraDNS to load a given zone file; the
   zone file in question must be pointed to in the mararc file. Note also
   that maradns must be restarted to reload the updated zone files.

   More complicated scripting, such as checking the serial number before
   loading a given zone, is left as an exercise for the reader.

Bailiwick

   For security reasons, the fetchzone client only allows records that end in
   the zone name to be in a given zone. In other words, let us suppose we
   have a zone for example.com that looks like this:

 example.com.      10.1.2.3
 www.example.com.  10.99.88.76
 www.google.com.   10.99.88.76

   fetchzone, when grabbing this zone, will disable the "www.google.com"
   record because it doesn't end with "example.com". The disabling will look
   something like this when the zone file is grabbled:

 example.com. 10.1.2.3
 www.example.com. 10.99.88.76
 # Disabled out-of-bailiwick record follows
 #www.google.com. 10.99.88.76
