Kubernetes (K8s)

Kubernetes is an open-source container orchestration platform commonly used to manage containerized application workloads. It provides declarative configuration and automation for container-based applications, and it can scale workloads efficiently with features such as Horizontal Pod Autoscaling (HPA).

• Update and upgrade the packages.

  bash

  ~$ sudo apt update && sudo apt upgrade -y && sudo apt autoremove -y
  

• Install the dependencies and add the repository required to install containerd.

  bash

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

• Install and configure containerd.

  bash

  ~$ sudo apt update
  ~$ sudo apt install -y containerd.io
  ~$ 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
  
  ~$ sudo systemctl restart containerd
  ~$ sudo systemctl enable containerd
  

• Load the required kernel modules.

  bash

  ~$ cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
    overlay
    br_netfilter
    EOF
  
  ~$ sudo modprobe overlay
  ~$ sudo modprobe br_netfilter
  

• Configure the required iptables and forwarding settings.

  bash

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

• Add the Kubernetes repository and install kubectl, kubelet, and kubeadm.

  bash

  ~$ sudo apt-get install -y apt-transport-https ca-certificates
  ~$ curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.28/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
  
  ~$ 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
  
  ~$ sudo apt-get update && sudo apt-get install -y kubelet kubeadm kubectl
  ~$ sudo apt-mark hold kubelet kubeadm kubectl
  

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Note: Run the following commands on the master node.

• Initialize the Kubernetes cluster on the master node.

  bash

  ~$ sudo kubeadm init --pod-network-cidr=10.244.XX.0/16
  ~$ mkdir -p $HOME/.kube
  ~$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  ~$ sudo chown $(id -u):$(id -g) $HOME/.kube/config
  

• Install Flannel as the pod network.

  bash

  ~$ wget https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
  ~$ kubectl apply -f kube-flannel.yml
  ~$ kubectl get pods --all-namespaces
  

• Retrieve the join token and CA certificate hash.

  bash

  ~$ sudo kubeadm token list
  ~$ sudo openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
  

"

Note: Run the following command on each worker node.

• Join the worker node to the cluster.
  bash

  ~$ sudo kubeadm join --token [TOKEN] [NODE-MASTER]:6443 --discovery-token-ca-cert-hash sha256:[TOKEN-CA-CERT-HASH]