OS Preparation (Ubuntu Server)¶

This section describes all system-level prerequisites required before installing Kubernetes using kubeadm.

The goal is to ensure:

system stability
Kubernetes compatibility
predictable and reproducible behavior across all nodes

All steps below must be applied on every node:

control plane
worker nodes

Base assumptions¶

OS: Ubuntu Server 22.04 LTS (or newer)
Architecture: amd64
Network: static IP or DHCP reservation
User has sudo privileges

Disable swap¶

Kubernetes requires swap to be disabled.
The kubelet will refuse to start if swap is enabled.

Disable swap immediately¶

sudo swapoff -a

Disable swap permanently¶

Edit /etc/fstab and comment out any swap entry:

sudo sed -i '/ swap / s/^/#/' /etc/fstab

Verify swap status¶

free -h

Expected output: Swap: 0B

swapon --show

Expected no output

Load required kernel modules¶

Kubernetes networking requires specific kernel modules.

Configure modules to load at boot¶

sudo tee /etc/modules-load.d/k8s.conf <<EOF
overlay
br_netfilter
EOF

Load modules immediately¶

sudo modprobe overlay
sudo modprobe br_netfilter

Verify loaded modules¶

lsmod | grep -E 'overlay|br_netfilter'

Configure kernel parameters (sysctl)¶

Kubernetes requires proper packet forwarding and bridge traffic handling.

Configure sysctl parameters¶

sudo tee /etc/sysctl.d/k8s.conf <<EOF
net.bridge.bridge-nf-call-iptables  = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward                = 1
EOF

Apply settings¶

sudo sysctl --system

Verify settings¶

sysctl net.bridge.bridge-nf-call-iptables
sysctl net.ipv4.ip_forward

Expected value: 1

Install container runtime (containerd)¶

Kubernetes requires a CRI-compatible container runtime. This lab uses containerd.

Install containerd¶

sudo apt-get update
sudo apt-get install -y containerd

Configure containerd¶

sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml

Enable systemd cgroup driver¶

Edit /etc/containerd/config.toml and ensure:

SystemdCgroup = true

You can do it automatically:

sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml

Restart and enable containerd¶

sudo systemctl restart containerd
sudo systemctl enable containerd

Verify containerd status¶

systemctl status containerd

Verify system readiness¶

Before moving forward, ensure the following: - swap is disabled - required kernel modules are loaded - sysctl parameters are applied - containerd is running

This node is now ready for Kubernetes installation using kubeadm.

Network ranges¶

Network type	CIDR
Home LAN	192.168.1.0/24
Pod Network	10.244.0.0/16

Key design decisions¶

Wired Ethernet only for cluster nodes
Static addressing for predictability
Dedicated Pod CIDR to avoid routing conflicts
Single control plane (home lab scope)

This topology provides a simple, stable and production-like foundation for Kubernetes experimentation.