Kubernetes Cluster Setup Guide

Master Node Configuration:
To set the hostname for your master node, execute the following command:

sudo hostnamectl set-hostname "kubemaster01.abcxyz.com"  
exec bash

Worker Nodes Configuration:
To set the hostname for the worker nodes, execute the following commands:

sudo hostnamectl set-hostname "kubenode01.abcxyz.com"   # 1st worker node  
sudo hostnamectl set-hostname "kubenode03.abcxyz.com"   # 2nd worker node  
exec bash  

Make sure to replace the placeholders with the appropriate node names as needed.

===
To configure each node, please add the following lines to the /etc/hosts file:

192.168.0.26   [kubemaster01.abcxyz.com](http://kubemaster01.abcxyz.com) kubemaster01  
192.168.0.25   [kubenode01.abcxyz.com](http://kubenode01.abcxyz.com) kubenode01  
192.168.0.28   [kubenode03.abcxyz.com](http://kubenode03.abcxyz.com) kubenode03 

This setup ensures that each node can correctly resolve the specified hostnames.

===
Run the following commands on all nodes:

1. Disable Swap and Add Kernel Parameters
   Execute the commands:

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

2. Load the Required Kernel Modules
   Ensure that you load the specified 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
$ sudo tee /etc/sysctl.d/kubernetes.conf <<EOT
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
EOT

Reload the changes mentioned above by executing the following command:

sudo sysctl --system

======

Install Containerd Runtime

We will be utilizing the containerd runtime for our Kubernetes cluster. To begin the installation of containerd, first, install its dependencies:

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

Enable Docker Repository

Next, enable the Docker repository by running the following commands:

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] <custom data-type="smartlink" data-id="id-0">https://download.docker.com/linux/ubuntu</custom> $(lsb_release -cs) stable"

Install Containerd

Now, execute the following commands to install containerd:

sudo apt update  
sudo apt install -y <custom data-type="smartlink" data-id="id-1">http://containerd.io</custom>

Configure Containerd

Configure containerd to start using systemd as the 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

Finally, complete the installation and start the containerd service:

sudo apt-get update  
sudo apt-get install -y containerd  
sudo systemctl start containerd  
sudo systemctl enable containerd

=====================

Add Apt Repository for Kubernetes

To add the apt repository for Kubernetes, execute:

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

=========

Install Kubectl, Kubeadm, and Kubelet on All Nodes

Run the following commands to install kubectl, kubeadm, and kubelet on all nodes:

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

• kubectl will be used for CLI commands.

• kubeadm will be used for Kubernetes.

• kubelet acts as the agent for worker nodes to communicate with the master.

=========

Initialize the Kubernetes Cluster

Now, we are ready to initialize the Kubernetes cluster. Run the following kubeadm command on the master node only:

sudo kubeadm init --control-plane-endpoint=[kubemaster01.abcxyz.com](http://kubemaster01.abcxyz.com)

===========

Configure Access to the Cluster

To start interacting with the cluster, execute 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

You can now run the following kubectl commands to view the cluster and node status:

kubectl cluster-info  
kubectl get nodes

===============

Install Calico Network Plugin

A network plugin is essential for enabling communication between pods in the cluster. To install the Calico network plugin from the master node, run:

kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.26.0/manifests/calico.yaml

Finally, verify the status of the pods in the kube-system namespace:

kubectl get pods -n kube-system

====================

# Test Your Kubernetes Cluster Installation

To verify your Kubernetes cluster installation, follow these steps:

1. **Deploy an NGINX-based application** and attempt to access it:
   ```bash
   kubectl create deployment nginx-app --image=nginx --replicas=2

2. Check the status of the NGINX application deployment:

   kubectl get deployment nginx-app

3. Expose the deployment as a NodePort:

   kubectl expose deployment nginx-app --type=NodePort --port=80

4. Run the following commands to view the service status:

   kubectl get svc nginx-app  
   kubectl describe svc nginx-app

Connecting to the Worker Nodes

To start using your cluster, execute the following commands as a regular user:

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

Alternatively, if you are the root user, you can run:

export KUBECONFIG=/etc/kubernetes/admin.conf

Next, you should deploy a pod network to the cluster. Execute the following command with one of the options listed at:
https://kubernetes.io/docs/concepts/cluster-administration/addons/

To join any number of control-plane nodes, copy the certificate authorities and service account keys on each node, then run the following command as root:

kubeadm join [kubemaster01.abcxyz.com:6443](http://kubemaster01.abcxyz.com:6443) --token 7c7581.yu5oehlvyrsh8vlz \\  
      --discovery-token-ca-cert-hash sha256:ab86309ee7e81976c23ca7be305d7788d180e2b6f8553052b2104733b277ed8c \\  
      --control-plane

To join any number of worker nodes, run the following command on each as root:

kubeadm join [kubemaster01.abcxyz.com:6443](http://kubemaster01.abcxyz.com:6443) --token 7c7581.yu5oehlvyrsh8vlz \\  
      --discovery-token-ca-cert-hash sha256:ab86309ee7e81976c23ca7be305d7788d180e2b6f8553052b2104733b277ed8c  

Output after Joining

After executing the join command, you should see output similar to the following:

root@kubenode01:/home/hcloud# kubeadm join [kubemaster01.abcxyz.com:6443](http://kubemaster01.abcxyz.com:6443) --token 7c7581.yu5oehlvyrsh8vlz \\  
      --discovery-token-ca-cert-hash sha256:ab86309ee7e81976c23ca7be305d7788d180e2b6f8553052b2104733b277ed8c  
[preflight] Running pre-flight checks  
[preflight] Reading configuration from the cluster...  
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'  
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"  
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"  
[kubelet-start] Starting the kubelet  
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has successfully joined the cluster:

• A certificate signing request was sent to the API server, and a response was received.

• The Kubelet was informed of the new secure connection details.

Run kubectl get nodes on the control-plane to see this node join the cluster.