How to create a multi-node Kubernetes local cluster for CKA, CKAD, CKS exams!

For this demo, we will create 2 Ubuntu nodes using Multipass. Also, we can use this cluster environment to practice for CKAD/CKA/CKS exams, because uses Ubuntu nodes.

1. Installing Multipass

We can install it on Linux, Windows and MacOS.

OS	Reference
Windows	https://multipass.run/docs/installing-on-windows
MacOS	https://multipass.run/docs/installing-on-macos
Linux	https://multipass.run/docs/installing-on-linux

I will use Homebrew for MacOS:

brew install --cask multipass

Verify the installation:

multipass

2. Create our Linux nodes (Ubuntu)

You should consider:

• 2 GiB or more of RAM per machine--any less leaves little room for your apps.
• At least 2 CPUs on the machine that you use as a control-plane node.

Launching master node:

multipass launch --name master --mem 2G --cpus 2 --disk 10G

Launching worker node:

multipass launch --name worker --mem 2G --cpus 2 --disk 10G

Verify nodes:

multipass ls

3. Login to the master node and install requirements

I installed k8s v1.22 for simulating CKA/CKAD/CKS exams, you can use another version if needed. Use crictl to manage containers inside the nodes (Docker does not work)

multipass shell master

Scale to root user:

sudo -i

Run those commands:

apt-get upgrade
apt-get update
apt-get install -y apt-transport-https ca-certificates curl

curl -fsSLo /usr/share/keyrings/kubernetes-archive-keyring.gpg https://packages.cloud.google.com/apt/doc/apt-key.gpg

echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" |  tee /etc/apt/sources.list.d/kubernetes.list

apt-get update
apt-get install -y kubeadm=1.22.4-00 kubelet=1.22.4-00 kubectl=1.22.4-00
apt-mark hold kubelet kubeadm kubectl

apt-get install containerd -y
mkdir -p /etc/containerd
containerd config default  /etc/containerd/config.toml

We need verify this file /etc/sysctl.conf and add:

net.bridge.bridge-nf-call-iptables = 1

After that, run:

sudo -s
sysctl --system
modprobe overlay
modprobe br_netfilter
hostnamectl set-hostname master
swapoff -a
echo '1' > /proc/sys/net/ipv4/ip_forward
exit

4. Initialize and configure the control plane node on master

kubeadm init

5. Setting up Kubeconfig file

mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config

6. Install Weave Net for Cluster Networking

kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

7. Generate a token to join our worker node

kubeadm token generate
kubeadm token create [[TOKEN]] --print-join-command

Copy and save the output to run on worker node

8. Login to the worker node and install requirements

multipass shell worker

Scale to root user:

sudo -i

Run those commands:

apt-get upgrade
apt-get update
apt-get install -y apt-transport-https ca-certificates curl

curl -fsSLo /usr/share/keyrings/kubernetes-archive-keyring.gpg https://packages.cloud.google.com/apt/doc/apt-key.gpg

echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" |  tee /etc/apt/sources.list.d/kubernetes.list

apt-get update
apt-get install -y kubeadm=1.22.4-00 kubelet=1.22.4-00
apt-mark hold kubelet kubeadm

apt-get install containerd -y
mkdir -p /etc/containerd
containerd config default  /etc/containerd/config.toml

We need verify this file /etc/sysctl.conf and add:

net.bridge.bridge-nf-call-iptables = 1

After that, run:

sudo -s
sysctl --system
modprobe overlay
modprobe br_netfilter
hostnamectl set-hostname worker
swapoff -a
echo '1' > /proc/sys/net/ipv4/ip_forward
exit

9. Join worker node to the cluster

Paste the output saved in step 6, something like this:

kubeadm join 192.168.64.3:6443 --token dmxxxc.o6n5qh3d561c568n --discovery-token-ca-cert-hash sha256:5ad0a04d3c5f3a1cadcc0720975b40359f58y1c44442000bd312785h1ea72ffc

10. Login to the master node and test your cluster

multipass shell master
sudo -i
kubectl get nodes -o wide

Kubernetes is ready. Now, you can practice on your multi-node cluster.

11. Delete cluster

If you need to delete your cluster, run these commands:

multipass stop master worker
multipass delete master worker

Happy hacking 😄 !!