DNS Server

Andreas is studying computer science at an online university. Please help him to master DNS by answering the following questions (note: Andreas prefers the term "Free Software" to "open-source"):

  1. What is DNS?
  2. What is the history of DNS?
  3. What problem does DNS solve?
  4. What are the strengths and weaknesses of DNS?
  5. How is DNS implemented as Free Software?
  6. Please show several fully explained examples of implementing DNS on a modern GNU/Linux computer system.

1. What is DNS?

DNS, or Domain Name System, is a hierarchical and decentralized naming system used for computers, services, or other resources connected to the Internet or a private network. It translates human-friendly domain names, such as www.example.com, into the IP addresses that computers use to identify each other on the network.

2. History of DNS

DNS was introduced in 1983 by Paul Mockapetris and Jon Postel to replace the old system where hostnames and IP addresses were mapped manually in a hosts.txt file, which was centrally managed and distributed to all connected computers. This older system wasn't scalable, and DNS was introduced as a solution to manage the rapid expansion of the internet.

3. Problem DNS Solves

DNS solves the problem of having to remember IP addresses. Instead of remembering a complicated string of numbers (IPv4) or alphanumeric characters (IPv6), users can access websites or network resources by typing human-readable and easy-to-remember domain names. DNS servers handle the mapping between domain names and IP addresses, making the internet much more user-friendly.

4. Strengths and Weaknesses of DNS

  • Strengths

    • Human Readability: Makes it easier for humans to access websites without having to remember complex IP addresses.
    • Scalability: Handles a vast number of domain names and IP addresses without central management.
    • Decentralization: Reduces single points of failure and allows for a distribution of control.
  • Weaknesses

    • Security: Vulnerable to attacks such as DNS spoofing and DDoS attacks.
    • Reliability: Sometimes DNS queries can fail, or there might be errors in DNS records.
    • Propagation Delays: Changes to DNS records (like changing an IP address for a domain) may take time to propagate across the internet.

5. DNS Implemented as Free Software

Several Free Software projects implement DNS services, such as BIND (Berkeley Internet Name Domain), Unbound, and PowerDNS.

  • BIND: One of the most widely used DNS servers. It’s comprehensive and has rich documentation but is somewhat complex.

  • Unbound: A lighter, more modern alternative focused on being a resolving DNS cache.

  • PowerDNS: Another powerful DNS server that is easy to manage and has robust performance.

6. Examples of Implementing DNS on a Modern GNU/Linux System

Example 1: Setting Up BIND as a Caching Nameserver

  1. Install BIND:

    sudo apt install bind9

    This installs the BIND9 DNS server on a Debian/Ubuntu system.

  2. Configure BIND:

    • Edit the configuration file:
      sudo nano /etc/bind/named.conf.options
    • Modify the file to configure a forwarder (if desired) or allow queries from your network.
  3. Restart BIND:

    sudo systemctl restart bind9

    This restarts the BIND service, applying the configurations.

Example 2: Querying DNS using Dig (A Tool Part of BIND Package)

  • Dig Command:
    dig @ www.example.com
    • This queries the DNS records for www.example.com using Google’s DNS server (
    • The @ specifies which DNS server to query.

Example 3: Setting up Unbound as a Caching Nameserver

  1. Install Unbound:

    sudo apt install unbound
  2. Configure Unbound:

    • Edit the configuration:
      sudo nano /etc/unbound/unbound.conf
    • Make the necessary adjustments, such as allowing queries from your network and setting forwarding servers.
  3. Restart Unbound:

    sudo systemctl restart unbound

These examples and the understanding of DNS's functioning and configuration will assist Andreas in mastering DNS as part of his computer science studies, keeping in line with his preference for Free Software.

This article was updated on October 30, 2023

You should also read:

Configure a caching DNS server

Lycia is a RHEL Sysadmin at Google: Her RHEL Server: Lycia_RHEL_Server_01 Her username: lycia.lycia Her preference: Linux commands must NEVER be run as…