Day 24. Create Kubernetes Cluster

Prerequisites

Before diving into the installation, ensure that your environment meets the following prerequisites:

• An Ubuntu 22.04 system.

• Minimum 2GB RAM or more.

• Minimum 2 CPU cores (or 2 vCPUs).

• 20 GB of free disk space on /var (or more).

• Custom ICMP rule for all nodes in Security Group

• Ensure machines in the cluster can ping each other via IP and hostname.

• Update and Upgrade Ubuntu (all nodes)

  Begin by ensuring that your system is up to date. Open a terminal and execute the following commands:

sudo apt update
sudo apt upgrade

• Disable Swap (all nodes)

  To enhance Kubernetes performance, disable swap and set essential kernel parameters. Run the following commands on all nodes to disable all swaps:

sudo swapoff -a
sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

• Add Kernel Parameters (all nodes)

  Load the required kernel modules on all nodes:

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

• Configure the critical kernel parameters for Kubernetes using the following

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

• Then, reload the changes:

sudo sysctl --system

• Install Containerd Runtime (all nodes)

  We are using the containerd runtime. Install containerd and its dependencies with the following commands:

sudo apt install -y curl gnupg2 software-properties-common apt-transport-https ca-certificates

• Enable the Docker repository:

sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmour -o /etc/apt/trusted.gpg.d/docker.gpg
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

• Update the package list and install containerd:

sudo apt update
sudo apt install -y containerd.io

• Configure containerd to start using systemd as cgroup:

containerd config default | sudo tee /etc/containerd/config.toml >/dev/null 2>&1
sudo sed -i 's/SystemdCgroup \= false/SystemdCgroup \= true/g' /etc/containerd/config.toml

• Restart and enable the containerd service:

sudo systemctl restart containerd
sudo systemctl enable containerd

• Add Apt Repository for Kubernetes (all nodes)

  Kubernetes packages are not available in the default Ubuntu 22.04 repositories. Add the Kubernetes repositories with the following commands:

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.28/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes.list
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.29/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
sudo apt update

• Install Kubectl, Kubeadm, and Kubelet (all nodes)

  After adding the repositories, install essential Kubernetes components, including kubectl, kubelet, and kubeadm, on all nodes with the following commands:

sudo apt install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

• Initialize Kubernetes Cluster with Kubeadm (master node)

  With all the prerequisites in place, initialize the Kubernetes cluster on the master node using the following Kubeadm command:

sudo kubeadm init

• After the initialization is complete make a note of the kubeadm join command for future reference.

  Run the following commands on the master node:

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

• Next, use kubectl commands to check the cluster and node status:

kubectl get nodes

• Add Worker Nodes to the Cluster (worker nodes)

  On each worker node, use the kubeadm join command you noted down earlier:

  Open port 6443 on all nodes

kubeadm join 172.31.26.104:6443 --token lit28c.xikm96pa63xb1c0k \
        --discovery-token-ca-cert-hash sha256:ef3b21607fc490f882e74366d16780de35bc0b3446af82e5a02f8a0e5bb712f4

• list all nodes on master-node

kubectl get nodes

• Install Kubernetes Network Plugin (master node)

  To enable communication between pods in the cluster, you need a network plugin. Install the Calico network plugin with the following command from the master node:

kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.25.0/manifests/calico.yaml

• Verify the cluster and test (master node)

  Finally, we want to verify whether our cluster is successfully created.

kubectl get pods -n kube-system
kubectl get nodes

• Deploy test application on cluster (master node)

kubectl run nginx --image=nginx