Introduction

Welcome to the “RKE2 the Hard Way” training series! In this series, we’ll embark on a journey to build a Kubernetes cluster from scratch—mimicking the robust features of Rancher Kubernetes Engine 2 (RKE2)—without relying on any distribution-specific tools or installers.

It’s called the “hard way” because we’ll manually configure and set up each component of the Kubernetes cluster. This approach is designed to provide a deep understanding of how Kubernetes works under the hood and to highlight the automation and simplification RKE2 provides.

By the end of this series, you’ll have a functional Kubernetes cluster with the following features:

  • A three-node etcd cluster for high availability.
  • All nodes acting as both control plane and worker nodes.
  • Ingress-Nginx for external access to applications.
  • CoreDNS for cluster DNS resolution.
  • Cilium CNI for networking and network policy.

This series is inspired by Kelsey Hightower’s “Kubernetes the Hard Way”, but adapted to build a cluster with features similar to RKE2. Our goal is to give you a comprehensive understanding of Kubernetes components, their interactions, and how to manually configure them, all while appreciating the work RKE2 does on our behalf.

Prerequisites

Before we begin, ensure you have the following in place:

1. Nodes

You’ll need at least three nodes (virtual machines or physical servers). These nodes should meet the following requirements:

  • Operating System: Ubuntu 24.04 or SUSE Linux Enterprise Server 15 SP5.
  • Architecture: x86_64 (amd64).
  • Container Runtime: containerd
  • CPU: 2+ cores
  • Memory: 4GB+ RAM
  • Disk: 20GB+ storage
  • Network: Connectivity between all nodes.
  • Hostname: Each node should have a unique hostname.
  • Time Synchronization: Ensure time sync is configured (ntpd or systemd-timesyncd).
  • Swap Disabled: Swap should be disabled on all nodes (Kubernetes requires this for optimal performance and scheduling).

⚙️ For the purposes of this training series, we will assume the nodes are named node01, node02, and node03. Adjust accordingly if your nodes have different hostnames.

2. Workstation Tools

Your local machine (workstation) should have the following tools installed:

3. Internet Access

Nodes will need access to the internet to download binaries and container images.

4. Container Runtime

For this guide, we will use containerd as the container runtime. Ensure containerd is installed and configured on all nodes. Refer to the containerd documentation for installation instructions: https://containerd.io/docs/getting-started/

5. Administrative Privileges

Ensure you have sudo privileges on all nodes.

Initial Node Setup

Before we begin installing components, let’s set up some basic configurations on our nodes to ensure they can communicate properly throughout the tutorial.

1. Configure /etc/hosts

On each node, let’s configure the /etc/hosts file to ensure that all nodes can reach each other by hostname:

# Run on all nodes
sudo cat >> /etc/hosts << EOF
# Kubernetes Nodes
192.168.1.101 node01
192.168.1.102 node02
192.168.1.103 node03
EOF

⚠️ Important: Replace the IP addresses above with the actual IP addresses of your nodes. These are just examples.

Verify connectivity by pinging the other nodes by hostname:

# Run these commands on each node to verify
ping -c 3 node01
ping -c 3 node02
ping -c 3 node03

2. Set Up SSH Keys for Certificate Distribution

Since we’ll be generating certificates on node01 and distributing them to the other nodes, let’s set up SSH keys to enable password-less SSH:

# Run these commands on node01

# Generate an SSH key if one doesn't already exist
[ ! -f ~/.ssh/id_rsa ] && ssh-keygen -t rsa -N "" -f ~/.ssh/id_rsa

# Copy the SSH key to node02 and node03
# You'll be prompted for the password of the remote users
ssh-copy-id node02
ssh-copy-id node03

Verify SSH access works correctly:

# Test SSH access (should connect without password prompt)
ssh node02 "hostname"
ssh node03 "hostname"

This will ensure that we can easily copy certificates and other files between nodes when needed.

Next Steps

Next, we will move to Part 2 and set up a Certificate Authority and generate TLS certificates for our Kubernetes cluster. This is a critical step that must be completed before setting up any components!

👉 Continue to Part 2: Certificate Authority and TLS Certificates