Building a Kubernetes Cluster from Scratch: A Detailed Guide

Anh Trần Tuấn - Aug 23 - - Dev Community

1. Prerequisites

Before we dive into the process, ensure you have the following prerequisites:

+ Linux servers : At least three servers (1 master node, 2 worker nodes) running Ubuntu 20.04 LTS.

+ Access to the internet : The nodes will need internet access to download and install packages.

2. Environment Setup

Ensure that these 3 virtual or physical machines can see each other. If you don't have 3 static IPs for them, you can set them up on the same LAN as follows:

+ Master Node : master-node (IP: 192.168.1.100)

+ Worker Node 1 : worker-node-1 (IP: 192.168.1.101)

+ Worker Node 2 : worker-node-2 (IP: 192.168.1.102)

2.1 Update and Upgrade the Servers

Start by updating and upgrading all your servers:

sudo apt-get update
sudo apt-get upgrade -y
Enter fullscreen mode Exit fullscreen mode

2.2 Install Docker

Kubernetes uses Docker as its container runtime. Install Docker on all three nodes:

sudo apt-get install -y docker.io
sudo systemctl enable docker
sudo systemctl start docker
Enter fullscreen mode Exit fullscreen mode

2.3 Install Kubernetes Components

We need to install kubeadm , kubelet , and kubectl on all nodes:

sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
sudo apt-add-repository "deb http://apt.kubernetes.io/ kubernetes-xenial main"
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
Enter fullscreen mode Exit fullscreen mode

2.4 Initialize the Kubernetes Master Node

On the master node, we'll initialize the cluster. This process sets up the control plane:

sudo kubeadm init --pod-network-cidr=10.244.0.0/16
Enter fullscreen mode Exit fullscreen mode

Once the initialization is complete, you'll see a command to join the worker nodes to the cluster. Save this command as we'll need it later.

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following 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

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/networking/

Then you can join any number of worker nodes by running the following on each as root:

  kubeadm join 192.168.1.100:6443 --token abcdef.0123456789abcdef 
        --discovery-token-ca-cert-hash sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef
Enter fullscreen mode Exit fullscreen mode

When I set up the initial master node, I encountered several errors.

container runtime is not running: output: level=fatal msg="validate service connection: CRI v1 runtime API is not implemented for endpoint "unix:///var/run/containerd/containerd.sock": rpc error: code = Unimplemented desc = unknown service runtime.v1.RuntimeService"
Enter fullscreen mode Exit fullscreen mode

So I do

sudo apt remove containerd
sudo apt update
sudo apt install containerd.io
sudo rm /etc/containerd/config.toml
sudo systemctl restart containerd
Enter fullscreen mode Exit fullscreen mode

When

E0616 21:27:18.529602 14900 run.go:74] "command failed" err="failed to run Kubelet: running with swap on is not supported, please disable swap! or set --fail-swap-on flag to false.
Enter fullscreen mode Exit fullscreen mode

The kubelet is operating with swap enabled, whereas Kubernetes explicitly discourages the use of swap.

So I do

sudo swapoff -a
sudo sed -i '/swap/d' /etc/fstab
sudo systemctl restart kubelet
sudo systemctl status kubelet
Enter fullscreen mode Exit fullscreen mode

If you encounter a port error

sudo fuser -k 6443/tcp
sudo fuser -k 10259/tcp
sudo fuser -k 10257/tcp
sudo fuser -k 10250/tcp
sudo fuser -k 2397/tcp
sudo fuser -k 2380/tcp

sudo rm /etc/kubernetes/manifests/kube-apiserver.yaml
sudo rm /etc/kubernetes/manifests/kube-controller-manager.yaml
sudo rm /etc/kubernetes/manifests/kube-scheduler.yaml
sudo rm /etc/kubernetes/manifests/etcd.yaml
sudo rm -r /var/lib/etcd
Enter fullscreen mode Exit fullscreen mode

3.1 Configure kubectl

To start using your cluster, configure kubectl for the current user:

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

3.2 Deploy a Pod Network

Kubernetes requires a Pod network to allow communication between nodes. We'll use Flannel:

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
Enter fullscreen mode Exit fullscreen mode

4. Join Worker Nodes to the Cluster

On each worker node, run the command provided by the master node after the initialization. It should look something like this:

sudo kubeadm join 192.168.1.100:6443 --token <token> --discovery-token-ca-cert-hash sha256:<hash>
Enter fullscreen mode Exit fullscreen mode

5. Verify the Cluster Setup

To verify that all nodes have joined the cluster, run:

kubectl get nodes -o wide
Enter fullscreen mode Exit fullscreen mode

You should see all three nodes (1 master and 2 workers) listed as ready.

6. Deploying a Sample Application

Let's deploy a simple Nginx application to verify that the cluster is working correctly.

Create a Deployment

We'll create an Nginx deployment:

kubectl create deployment nginx --image=nginx
Enter fullscreen mode Exit fullscreen mode

Expose the Nginx deployment as a service:

kubectl expose deployment nginx --port=80 --type=NodePort
Enter fullscreen mode Exit fullscreen mode

Verify the Deployment

kubectl get pods
Enter fullscreen mode Exit fullscreen mode

The output should show one Nginx pod running

Find the NodePort assigned to the Nginx service:

kubectl get service nginx
Enter fullscreen mode Exit fullscreen mode

Access the Nginx service using the
:

in your browser. You should see the Nginx welcome page.

7. Scaling the Application

Let's scale the Nginx deployment to 3 replicas to see how Kubernetes manages multiple instances:

kubectl scale deployment nginx --replicas=3
Enter fullscreen mode Exit fullscreen mode

Verify the scaling:

kubectl get pods
Enter fullscreen mode Exit fullscreen mode

You should see three Nginx pods running.

8. Cleaning Up

To clean up the deployment and service:

kubectl delete service nginx
kubectl delete deployment nginx
Enter fullscreen mode Exit fullscreen mode

9. Typical installation problems

9.1 When encountering the FORBIDDEN 

sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
 sudo chown $(id -u):$(id -g) $HOME/.kube/config
 kubectl get pv
 kubectl get deploy
Enter fullscreen mode Exit fullscreen mode

9.2 Couldn't get current server API 

E0703 22:36:32.702012 9430 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0703 22:36:32.702614 9430 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0703 22:36:32.705110 9430 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0703 22:36:32.705619 9430 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
E0703 22:36:32.707190 9430 memcache.go:265] couldn't get current server API group list: Get "http://localhost:8080/api?timeout=32s": dial tcp 127.0.0.1:8080: connect: connection refused
The connection to the server localhost:8080 was refused - did you specify the right host or port?
Enter fullscreen mode Exit fullscreen mode

Solution:

Step 1: On “Worker node/Compute node” look for file "/etc/kubernetes/admin.conf ", If it is not available than “Copy paste/SCP” from your “Controller node/master node”.

Step 2: On “Worker Node/Compute node” create a directory called “.kube” on user home directory, if it is already exist than Not to worry and move inside this directory.

mkdir ~/.kube
or,
mkdir -p $HOME/.kube
cd ~/.kube
Enter fullscreen mode Exit fullscreen mode

Step 3: Create file called “config” and paste the content of “/etc/kubernetes/admin.conf”.

vi config
Enter fullscreen mode Exit fullscreen mode

Note:- while Copy the content on config file make sure the below mention parameter has correct master IP mentioned, Some time it is localhost but try to update master IP.

10. Conclusion

In this guide, we've successfully set up a Kubernetes cluster from scratch, deployed a sample application, and verified its functionality. Building a Kubernetes cluster manually gives you a deeper understanding of the underlying infrastructure and how Kubernetes operates. This knowledge is essential for troubleshooting and optimizing your cluster in a production environment.

By following this guide, you're now equipped to create and manage your Kubernetes clusters, deploy applications, and scale them according to your needs. Happy clustering!

Read posts more at : Building a Kubernetes Cluster from Scratch: A Detailed Guide

Image
Transform Your Customer Relationships with the Leading Open Source CRM: Twenty!

opensource, startup, saas, productivity
Image
Avoid Making This Fatal Mistake On Your Mental Health Test
Image
„Meble, które mówią: Stwórz przestrzeń pełną charakteru!”
Image
10 Things You Learned In Preschool That Can Help You In Accidents Lawyer
Image
You Are Responsible For A Lost Car Key Budget? 12 Top Ways To Spend Your Money
Image
Why Accident Lawyers Bronx Is Everywhere This Year
Image
Apple’s iOS 18 Health App Development | Top 10 Features to Revolutionize Healthcare

mobile, ios
Image
Bermacam Keuntungan Taruhan Judi Online Lewat Handphone
Image
7 Small Changes That Will Make A Huge Difference In Your Remote Key Fob Repair
Image
Why Key Repair Is Your Next Big Obsession
Image
An Injury Accident Lawyers Success Story You'll Never Imagine
Image
10 Lost A Car Key-Friendly Habits To Be Healthy
Image
Filament: Modify login or logout response

filament, laravel, authentication
Image
Where Can You Find The Best Bifold Door Repair Near Me Information?
Image
Accident Lawyer Brooklyn's History History Of Accident Lawyer Brooklyn
Image
The 12 Best Built In Electric Fireplace Wall Accounts To Follow On Twitter
Image
A Look At Car Keys Lost Replacement's Secrets Of Car Keys Lost Replacement
Image
Why No One Cares About Keys Repair
Image
How Much to Install a Cat Flap
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .