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Unni P
Unni P

Posted on • Updated on • Originally published at iamunnip.hashnode.dev

Building a Kubernetes v1.28 Cluster using kubeadm

#kubernetes #cloudnative #opensource #beginners

In this article, we will look how we can set up a three node Kubernetes v1.28 cluster using kubeadm

Introduction

  • kubeadm is a tool used to create Kubernetes clusters

  • It automates the creation of Kubernetes clusters by bootstrapping the control plane, joining the nodes etc

  • Follows Kubernetes release cycle

  • Open-source tool maintained by the Kubernetes community

Prerequisites

  • Create three Ubuntu 20.04 LTS instances for the control plane, node-1 and node-2

  • Each instance has a minimum specification of 2 CPU and 2 GB RAM

  • Networking must be enabled between instances

  • Required ports must be allowed between instances

  • Swap must be disabled on instances

Initial Configuration

Set up unique hostnames on the control-plane, node-1 and node-2

Once the hostnames are set, log out from the current session and log back in to reflect the changes

# control-plane

sudo hostnamectl set-hostname control-plane
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# node-1

sudo hostnamectl set-hostname node-1
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# node-2

sudo hostnamectl set-hostname node-2
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Update the hosts file on the control-plane, node-1 and node-2 to enable communication via hostnames

# control-plane, node-1 and node-2

sudo vi /etc/hosts

172.31.91.254 control-plane
172.31.94.177 node-1
172.31.87.11 node-2
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Disable swap on control-plane, node-1 and node-2 and if a swap entry is present in the fstab file then comment out the line

# control-plane, node-1 and node-2

sudo swapoff -a

sudo vi /etc/fstab
  # comment out swap entry
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To set containerd as our container runtime on control-plane, node-1 and node-2, first, we need to load some Kernel modules and modify system settings

# control-plane, node-1 and node-2

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

sudo modprobe overlay

sudo modprobe br_netfilter
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# control-plane, node-1 and node-2

cat << EOF | sudo tee /etc/sysctl.d/99-kubernetes-cri.conf
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sudo sysctl --system
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Installation

Once the Kernel modules are loaded and the system settings are modified, now we can install containerd runtime on control-plane, node-1 and node-2

# control-plane, node-1 and node-2

sudo apt update

sudo apt install -y containerd
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Once the packages are installed, generate a default configuration file for containerd on control-plane, node-1 and node-2 and restart the containerd service

# control-plane, node-1 and node-2

sudo mkdir -p /etc/containerd

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

sudo systemctl restart containerd
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We need to install some prerequisite packages on control-plane, node-1 and node-2 for configuring the Kubernetes package repository

# control-plane, node-1 and node-2

sudo apt update

sudo apt install -y apt-transport-https ca-certificates curl
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Download the Google Cloud public signing key and configure Kubernetes apt repository on control-plane, node-1 and node-2

# control-plane, node-1 and node-2

sudo mkdir -p /etc/apt/keyrings

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
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Install kubeadm, kubelet and kubectl tools and hold their package version on control-plane, node-1 and node-2

# control-plane, node-1 and node-2

sudo apt update

sudo apt install -y kubeadm kubelet kubectl

sudo apt-mark hold kubeadm kubelet kubectl
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Initialize the cluster by executing the below command on control-plane

# control-plane

sudo kubeadm init --pod-network-cidr 192.168.0.0/16 --kubernetes-version 1.28.0
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Once the installation is completed, set up our access to the cluster on control-plane

# control-plane

mkdir -p $HOME/.kube

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

sudo chown $(id -u):$(id -g) $HOME/.kube/config
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Verify our cluster status by listing the nodes

But our nodes are in a NotReady state because we haven’t set up networking

# control-plane

kubectl get nodes
NAME            STATUS     ROLES           AGE   VERSION
control-plane   NotReady   control-plane   40s   v1.28.0
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Install the Calico network addon to the cluster and verify the status of the nodes

# control-plane

kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.26.1/manifests/calico.yaml
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# control-plane

kubectl get nodes
NAME            STATUS   ROLES           AGE    VERSION
control-plane   Ready    control-plane   101s   v1.28.0
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Once the networking is enabled, join our workload nodes to the cluster

Get the join command from the control-plane

# control-plane

kubeadm token create --print-join-command
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Once the join command is retrieved from the control-plane, execute them in node-1 and node-2

# node-1 and node-2

sudo kubeadm join 172.31.91.254:6443 --token o3in76.aeqii9shr86cem2w --discovery-token-ca-cert-hash sha256:e301651b8930363842b054bafec26aba718dbc724d903c4c73228703622dc5f1
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Verify our cluster and all the nodes will be in a Ready state

# control-plane

kubectl get nodes
NAME            STATUS   ROLES           AGE     VERSION
control-plane   Ready    control-plane   2m55s   v1.28.0
node-1          Ready    <none>          28s     v1.28.0
node-2          Ready    <none>          19s     v1.28.0
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Application Deployment

Deploy an Nginx pod, expose it as ClusterIP and verify its status

# control-plane

kubectl run nginx --image=nginx --port=80 --expose
service/nginx created
pod/nginx created

kubectl get pod nginx -o wide
NAME    READY   STATUS    RESTARTS   AGE   IP              NODE     NOMINATED NODE   READINESS GATES
nginx   1/1     Running   0          17s   192.168.247.1   node-2   <none>           <none>

kubectl get svc nginx
NAME    TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
nginx   ClusterIP   10.97.157.101   <none>        80/TCP    38s
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That's all for now

Reference

https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/

Top comments (1)

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cwprogram profile image
Chris White •

Thanks for the write up! I felt it had a good overview of how the kubernetes installation process works. One thing that caught my eye was swap being disabled. This lead me to find an interesting discussion on the project's GitHub issues. Apparently they're working on support for Linux swap in kubernetes, where it graduate to beta in 1.28. If anyone's interested you can check the current progress in this issue.

Thanks for the solid article!

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