How to set up a secondary DNS server in CentOS

In the previous tutorial, we created a primary DNS server (ns1) for a test domain example.tst. In this tutorial, we will create a secondary DNS server (ns2) for the same domain by using bind package on CentOS. When it comes to setting up a secondary DNS server, the following factors should be kept in mind. You do NOT need to manually create forward and reverse zone files in the secondary DNS server. The zone files will be periodically synced from the primary DNS server automatically.