These steps are done in the Slave DNS server

These steps are done in the Slave DNS server

The objective of this section is to configure the slave DNS server to fetch a zone information file from the master DNS server, place the file in a location that is accessible to BIND, and then apply those zones to BIND by restarting the application. To do that you need to create a script.
Create a text file and paste the following code into it:

#!/bin/sh

wget http://entomy.com/dns/updatedenver.txt -O /var/named/chroot/var/named/slaves/dallas.conf
/etc/init.d/named restart

The wget statement fetches the file from the master DNS server, and then saves it as a file called dallas.conf in the specified location. You will need to edit the URL of the text file location to the actual web accessible location you put it in on the master DNS server. Likewise, edit the name and location of the .conf file to your liking. When done, save the file. I called the file getdallas, since my master DNS server is in Dallas, and saved it in the var/named/chroot/var/named/slaves/ directory, the same location as I put the .conf file.

Now open your named.conf file (normally found in /etc) and place this statement at the end of the file.

include "/var/named/chroot/var/named/slaves/dallas.conf";

You will need to edit the path and file name to match the location of the .conf file you specified in the script. Save the file. Also not that if BIND is running “chrooted” (as it is under Kloxo) that the path will be shortened to make the command look like this.

include "/var/named/slaves/dallas.conf";

Now login to SSH as root and create the .conf file so it can be written to by your script, editing for the proper path and file name, of course.

# touch /var/named/chroot/var/named/slaves/dallas.conf

Create the directory for the zone files to be created in, make the directory writable, and then restart BIND.

# mkdir /var/named/chroot/var/named/slaves/dallas/
# mkdir /var/named/chroot/var/named/slaves/dallas/named/
# chmod 777 /var/named/chroot/var/named/slaves/dallas/
# chown named:named /var/named/chroot/var/named/slaves/dallas/
# chmod 777 /var/named/chroot/var/named/slaves/dallas/named/
# chown named:named /var/named/chroot/var/named/slaves/dallas/named/ # /etc/rc.d/init.d/named restart
Of course, all of the above can be done a lot quicker & easier using the webmin file manager, but it works fine from the command prompt.
With those tasks done, test run the script from the command prompt.
/var/named/chroot/var/named/slaves/getdallas
With any luck, your output will look like this.
You can see from the output that the file was fetched, saved in the proper location, then named was restarted successfully.

Once you have the script running the way you want it to, create a cron job to run the script soon after the script on the master DNS server runs. Scheduling the scripts to run once or twice an hour is normally sufficient for redundant DNS.

Note that the zone files that were created from these scripts will be empty files. These scripts are only intended to make the slave DNS server aware of changes in the master DNS server zone listing. You will need to configure another solution to fetch the zone file contents, such as AXFR, rsync, or scp. However, it’s important to note that any zone files that existed in the slave DNS server before the script was run that already contained zone details will not be overwritten.