You may continue to install Kubernetes on the vm you already installed docker. If you are installing this on a different machine make sure docker is already installed.

Part 1

Installing kubeadm, kubelet, and kubectl:

1. Update the apt package index:

sudo apt-get update

2. Install packages needed to use the Kubernetes apt repository:

sudo apt-get install -y apt-transport-https ca-certificates curl vim git

3. Download the public signing key for the Kubernetes package repositories:

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.28/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

4. Add the Kubernetes apt repository:

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

Update the apt package index again:

sudo apt-get update

5. Install kubelet, kubeadm, and kubectl:`

sudo apt-get install -y kubelet kubeadm kubectl

6. Pin installed versions of kubelet, kubeadm, and kubectl to prevent them from being accidentally updated:

sudo apt-mark hold kubelet kubeadm kubectl

7. Check installed versions:

kubectl version --client

kubeadm version

Disable Swap Space

8. Disable all swaps from /proc/swaps.

sudo swapoff -a

sudo sed -i.bak -r 's/(.+ swap .+)/#\1/' /etc/fstab

9. Check if swap has been disabled by running the free command.

free -h

Install Container runtime

10. Configure persistent loading of modules

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

11. Load at runtime

sudo modprobe overlay

sudo modprobe br_netfilter

12. Ensure sysctl params are set

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

13. Reload configs

sudo sysctl --system

14. Install required packages

sudo apt install -y containerd.io

15. Configure containerd and start service

sudo mkdir -p /etc/containerd

sudo containerd config default | sudo tee /etc/containerd/config.toml

16. Configuring a cgroup driver

Both the container runtime and the kubelet have a property called "cgroup driver", which is essential for the management of cgroups on Linux machines.

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

17. Restart containerd

sudo systemctl restart containerd

sudo systemctl enable containerd

systemctl status containerd

Initialize control plane

18. Make sure that the br_netfilter module is loaded:

lsmod | grep br_netfilter

Output should similar to:

br_netfilter           22256  0 
bridge                151336  1 br_netfilter

19. Enable kubelet service.

sudo systemctl enable kubelet

20. Pull container images (it will take some time):

sudo kubeadm config images pull --cri-socket /run/containerd/containerd.sock

21. Bootstrap the endpoint. Here we use 10.244.0.0/16 as the pod network:

sudo kubeadm init --pod-network-cidr=10.244.0.0/16 --cri-socket /run/containerd/containerd.sock

You will see Your Kubernetes control-plane has initialized successfully!

You need to save the kubeadm join token string on a text document for future use.

22. To start the cluster, you need to run the following as a regular user (For this scenario we will only use a single master):

mkdir -p $HOME/.kube

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

sudo chown $(id -u):$(id -g) $HOME/.kube/config

23. Check cluster info:

kubectl cluster-info

24. Install a simple network plugin.

wget https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml

kubectl apply -f kube-flannel.yml

25. Check the plugin is working

kubectl get pods -n kube-flannel

26. Confirm master node is ready: (If you see the status as Notready, give it a around 10mins)

kubectl get nodes -o wide

27. On a master/ control node to query the nodes you can use:

kubectl get nodes

28. Connecting Worker nodes:
    1. Install docker on both worker nodes as per the guidelines here (Upto step 6).
    2. Install Kubernetes on each worker nodes. Follow above steps 1 to 20.
    3. Use previously saved kubeadm join token string to connect the workers. Run it with sudo.

[OPTIONAL] If you forgot the token, run the following on your master to create a new token:

kubeadm token create --print-join-command

But remember, this will create a new token.

4. After all workers are connected, check status of the cluster: Here after all commands should be run on the master.

kubectl get nodes -o wide

Part 2

Create a file simple-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.14.2
    ports:
    - containerPort: 80

To create the Pod shown above, run the following command:

kubectl apply -f simple-pod.yaml

Check pod

kubectl get pods

Kill the Pod.

kubectl delete pod nginx

Pods are generally not created directly and are created using workload resources.

See Working with Pods​https://kubernetes.io/docs/concepts/workloads/pods/#working-with-pods for more information on how Pods are used with workload resources

Part 3

Deploying a Simple Web Application on Kubernetes

1. Create a Deployment Manifest:

A Deployment ensures that a specified number of pod replicas are running at any given time. Let's create a simple Deployment for a web application using the nginx image. Save the following YAML to a file named webapp-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp-deployment
  labels:
    app: webapp
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80

2. Create a Service Manifest:

A Service is an abstraction that defines a logical set of Pods and enables external traffic exposure, load balancing, and service discovery. For our web application, we'll use a NodePort service.

Save the following YAML to a file named webapp-service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: webapp-service
spec:
  selector:
    app: webapp
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
      nodePort: 30080
  type: NodePort

3. Deploy the Application:

Apply the Deployment and Service manifests:

kubectl apply -f webapp-deployment.yaml

kubectl apply -f webapp-service.yaml

4. Verify the Deployment:

Check the status of the Deployment and Service:

kubectl get deployments

kubectl get services

You should see your webapp-deployment with 2 replicas. Give it a time to take both replicas online.

5. Access the Web Application:

Since we used a NodePort service, the web application should be accessible on node's IP at port 30080. If you're unsure of your node IPs, you can get them with:

kubectl get nodes -o wide

Then, in a web browser or using a tool like curl, access the web application:

curl http://<MASTER/NODE_IP>:30080

You should see the default nginx welcome page, indicating that your web application is running.

Delete all the deployments, run below command:

kubectl delete deployment <deployment name>

Delete all the Services, run below command:

kubectl delete service <service name>

Part 4

Deploying WordPress and MySQL on Kubernetes

Installing dependancies:

Download rancher.io/local-path storage class:

kubectl apply -f https://raw.githubusercontent.com/rancher/local-path-provisioner/master/deploy/local-path-storage.yaml

Check with kubectl get storageclass

Make this storage class (local-path) the default:

kubectl patch storageclass local-path -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

1. Create a PersistentVolumeClaim for MySQL:

MySQL needs persistent storage to store its data. Save the following YAML to a file named mysql-pvc.yaml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Apply the PVC:

kubectl apply -f mysql-pvc.yaml

2. Deploy MySQL:

Save the following YAML to a file named mysql-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - name: mysql
        image: mysql:5.7
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: "password"
        - name: MYSQL_DATABASE
          value: "wordpress"
        ports:
        - containerPort: 3306
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pvc

Apply the Deployment:

kubectl apply -f mysql-deployment.yaml

3. Create a Service for MySQL:

This will allow WordPress to communicate with MySQL. Save the following YAML to a file named mysql-service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  selector:
    app: mysql
  ports:
    - protocol: TCP
      port: 3306
      targetPort: 3306

Apply the Service: kubectl apply -f mysql-service.yaml

4. Deploy WordPress:

Save the following YAML to a file named wordpress-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpress
spec:
  replicas: 1
  selector:
    matchLabels:
      app: wordpress
  template:
    metadata:
      labels:
        app: wordpress
    spec:
      containers:
      - name: wordpress
        image: wordpress:latest
        env:
        - name: WORDPRESS_DB_HOST
          value: mysql
        - name: WORDPRESS_DB_USER
          value: "root"
        - name: WORDPRESS_DB_PASSWORD
          value: "password"
        ports:
        - containerPort: 80

Apply the Deployment: kubectl apply -f wordpress-deployment.yaml

5. Create a Service for WordPress:

This will expose WordPress to external traffic. Save the following YAML to a file named wordpress-service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: wordpress
spec:
  selector:
    app: wordpress
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: NodePort

Apply the Service:

kubectl apply -f wordpress-service.yaml

6. Access WordPress:

Since we used a NodePort service, WordPress should be accessible on node's IP at a dynamically allocated port above 30000. To find the NodePort assigned to WordPress:

kubectl get svc wordpress

Then, in a web browser, access WordPress:

http://< INTERNAL-IP>:<NODE_PORT>

Part 5

Convert your Docker deployment into a Kubernetes deployment, you may compose your own service, deployment manifests as needed. Use the docker images you used previously when creating the pods/deployments.

Additional ref:[ ​https://kubebyexample.com/]