Building a Kubernetes Cluster from Scratch - Part 1: Environment Setup

There are multiple tools to install Kubernetes. A community supported tool is kubeadm and this lab uses it to install and build a Kubernetes cluster.

Connecting to future control plane and worker nodes

I'm using AWS to launch two instances that will be my Kubernetes cluster. Both instances are Ubuntu 24.04 with 2vCPUs and 8GB of RAM. Using my AWS key pair, the next step is to connect to both instances using ssh.

Installing Kubernetes

The first step is to connect to the first EC2 instance to update and upgrade the control plane or cp.

$ ssh -i /path/to/my-key.pem ubuntu@instance-ip
$ sudo -i
root@cp:~# apt update && apt upgrade -y

With the system updated, the next step is to install a container runtime. A commonly used option, easy to deploy and lightweight is containerd. Also, Kubernetes has deprecated Docker engine as of 2020, and containerd offers simplicity and focus as it doesn't include the additional stuff that Docker includes. This is purely a container runtime which supports the Container Runtime Interface or CRI as expected by Kubernetes.

We need to install some dependencies.

root@cp:~# apt install apt-transport-https software-properties-common ca-certificates socat -y

Next, two kernel modules need to be loaded due to Kubernetes infrastructure requirements. They enable core container and networking functionality that Kubernetes needs. The overlay module relates to storage management and the br_netfilter module relates to networking and packet routing.

root@cp:˜# modprobe overlay
root@cp:˜# modprobe br_netfilter

Finally, we need to tweak the network routing and policies as Kubernetes relies on iptables rules. Without creating the rules below, network packets may bypass iptables rules and inter-pod communication would fail. The below command creates a configuration file kubernetes.conf at /etc/sysctl.d and it's loaded when the system starts. The two lines below, starting with net.bridge… ensure that IPv4 and IPv6 packets follow iptables rules. Finally, ip_forward enables IP forwarding in the Linux kernel.

root@cp:˜# cat << EOF | tee /etc/sysctl.d/kubernetes.conf
> net.bridge.bridge-nf-call-ip6tables = 1
> net.bridge.bridge-nf-call-iptables = 1
> net.ipv4.ip_forward = 1
EOF

Once those rules have been added, we ensure the changes are loaded by the current kernel.

root@cp:~# sysctl --system

That's part 1 on this series. The next part will deal with the installation of the containerd runtime and the Kubernetes software itself.