How to Configure Primary and Secondary DNS Server in Linux?

Configuring Primary and Secondary DNS servers in Linux is a crucial step in ensuring a stable and reliable network connection. The Domain Name System (DNS) plays a vital role in translating human-readable domain names into IP addresses, facilitating seamless communication across the internet. In this guide, we'll delve into the step-by-step process of configuring both Primary and Secondary DNS servers on a Linux system.

Setting Up Primary DNS Server:

To configure the Primary DNS server on your Linux machine, follow these steps:

1. Install DNS Server Software:
   Depending on your Linux distribution, use the package manager to install the DNS server software. For example, on Ubuntu, you can use the following command:

   sudo apt-get install bind9
   

2. Configure DNS Server:
   Edit the DNS server configuration file. For BIND, the configuration file is usually located at /etc/bind/named.conf.options. Open the file using a text editor:

   sudo nano /etc/bind/named.conf.options
   

3. Specify Primary DNS IP:
   Locate the 'forwarders' section in the configuration file and add the IP address of your desired Primary DNS server. Save and exit the text editor.

4. Restart DNS Service:
   Restart the DNS service to apply the changes:

   sudo service bind9 restart
   

Setting Up Secondary DNS Server:

Configuring the Secondary DNS server involves similar steps:

1. Install DNS Server Software:
   Install the DNS server software on the secondary server using the appropriate package manager. For BIND, use:

   sudo apt-get install bind9
   

2. Configure DNS Server:
   Edit the DNS server configuration file on the secondary server. Open the file with a text editor:

   sudo nano /etc/bind/named.conf.options
   

3. Specify Secondary DNS IP:
   In the 'forwarders' section, add the IP address of your Primary DNS server. Save and exit the file.

4. Set Up Zone Transfers:
   Open the primary DNS server configuration file, typically located at /etc/bind/named.conf.local. Add a configuration block for allowing zone transfers to the secondary server:

   zone "example.com" {
       type master;
       file "/etc/bind/db.example.com";
       allow-transfer { secondary_dns_ip; };
   };
   

5. Restart DNS Service:
   Restart the DNS service on both servers to apply the changes:

   sudo service bind9 restart
   

Verifying Configuration:

To ensure that the configuration is successful, use the following commands:

1. Check DNS Service Status:

   sudo service bind9 status
   

2. Test DNS Resolution:
   Use the nslookup command to verify if the DNS server is resolving domain names correctly:

   nslookup example.com
   

Congratulations! You have successfully configured Primary and Secondary DNS servers on your Linux machines. This ensures a robust and redundant DNS infrastructure, enhancing the reliability of your network.