Comprehensive Guide to Knot DNS with Real-World Examples

Knot DNS is a high-performance, authoritative-only DNS server developed for modern DNS needs. It is lightweight, efficient, and scalable, making it a great choice for use cases ranging from individual setups to enterprise-grade DNS infrastructure. In this guide, we will cover its installation, configuration, and monitoring, along with real-world examples to help you understand its use in practical scenarios.

1. Installation

Step 1: Update Your System

Ensure your system is up-to-date:

sudo apt update && sudo apt upgrade -y

Step 2: Add Knot DNS Repository

Knot DNS is not included in Ubuntu’s default repositories. Add the Knot DNS repository:


sudo apt install software-properties-common -y
sudo add-apt-repository ppa:cz.nic-labs/knot-dns -y

Step 3: Install Knot DNS

Install Knot DNS using:

sudo apt install knot-dns -y

Step 4: Verify Installation

Check the version to confirm Knot DNS is installed:

knotc --version

2. Configuration

Knot DNS uses configuration files located at /etc/knot. Its main configuration file is knot.conf. Here’s how to configure it step by step:

Step 1: Backup Default Configuration

Before making changes, back up the default configuration:

sudo cp /etc/knot/knot.conf /etc/knot/knot.conf.backup

Step 2: Define Zones

Edit the configuration file to add zones:

sudo nano /etc/knot/knot.conf

Example configuration for a DNS zone:


server:
  listen: [0.0.0.0@53, ::@53]

zone:
  - domain: example.com
    storage: "/var/lib/knot/"
    file: "example.com.zone"

Step 3: Create a Zone File

Create the zone file with DNS records:

sudo nano /var/lib/knot/example.com.zone

Example zone file:


$ORIGIN example.com.
@       3600 IN SOA ns1.example.com. admin.example.com. (
                2024112201 ; Serial
                3600       ; Refresh
                1800       ; Retry
                1209600    ; Expire
                3600 )     ; Minimum TTL
        IN NS   ns1.example.com.
ns1     IN A    192.168.1.10
www     IN A    192.168.1.20

Step 4: Start and Enable Knot DNS

Start Knot DNS and enable it to start at boot:

sudo systemctl start knot
sudo systemctl enable knot

3. Real-World Examples

Example 1: Hosting a Corporate Website

Knot DNS can be used as the authoritative DNS server for a corporate website. For example:

Company domain: company.com
Primary DNS server: ns1.company.com
Web server IP: 203.0.113.10

Configure the zone as:


zone:
  - domain: company.com
    storage: "/var/lib/knot/"
    file: "company.com.zone"

Zone file:


$ORIGIN company.com.
@       3600 IN SOA ns1.company.com. admin.company.com. (
                2024112201 ; Serial
                3600       ; Refresh
                1800       ; Retry
                1209600    ; Expire
                3600 )     ; Minimum TTL
        IN NS   ns1.company.com.
ns1     IN A    203.0.113.1
www     IN A    203.0.113.10

Example 2: DNS for Internal Networks

Knot DNS can serve as a local DNS server for internal networks:

Internal domain: internal.local
DNS server IP: 192.168.1.1

Configure Knot DNS to resolve internal services:


zone:
  - domain: internal.local
    storage: "/var/lib/knot/"
    file: "internal.local.zone"

Zone file:


$ORIGIN internal.local.
@       3600 IN SOA dns.internal.local. admin.internal.local. (
                2024112201 ; Serial
                3600       ; Refresh
                1800       ; Retry
                1209600    ; Expire
                3600 )     ; Minimum TTL
        IN NS   dns.internal.local.
dns     IN A    192.168.1.1
server1 IN A    192.168.1.100

4. Ensuring Stability and Monitoring

Use Systemd for Stability

Enable Knot DNS to restart on failure:


sudo systemctl enable knot
sudo systemctl start knot

Monitor Knot DNS Logs

Check logs to monitor DNS activity and troubleshoot issues:

journalctl -u knot

Integrate Monitoring Tools

Prometheus: Use node exporters to monitor server performance.
Grafana: Visualize Knot DNS metrics and set up alerts for downtime.

5. Testing Knot DNS

Test DNS Resolution

Use the dig command to test DNS resolution:

dig @localhost www.example.com

Validate Zone Configuration

Run the following to validate the zone:

knotc zone-check example.com

6. Restarting Knot DNS After Changes

After making changes, restart Knot DNS to apply them:

sudo systemctl restart knot

7. Uninstalling Knot DNS

If you need to remove Knot DNS:

sudo apt purge knot-dns -y

Remove configuration files:

sudo rm -rf /etc/knot /var/lib/knot

With these steps, you can install, configure, and manage Knot DNS effectively. The real-world examples provide practical insights into how Knot DNS can be used in various scenarios, from hosting websites to managing internal networks. This guide ensures a robust and scalable DNS setup tailored to your needs.

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