Kubeadm is a tool you can use to quickly standup a Kubernetes cluster. Here I will show you how to deploy K8S on Ubuntu 22.04. I will use 2 scripts that you can easily understand if you are fairly conversant with Linux batch scripting but if you're not familiar with scripting, just copy and paste!

Let's take note of the following:

1. The Kubernetes Architecture comprises of a  control node and worker nodes. For High Avaulability (HA ), you can configure  multiple nodes (like 3 nodes) as the control node but here I did'nt show you how to configure HA. You can use this for only 1 master  node and multiple worker nodes.
2. Deploying a kubernetes cluster comprises of 4 major steps:
   • Configure the required prerequisites on the Ubuntu servers (loading the bridge kernel modules, etc)
   • Install and configure the Container Runtime Interface (CRI) ( Docker, cri-o and Containerd). Here we used CRI-O
   • Install and configure Kubernetes components (kube-api, kube-scheduler, kube-controller)
   • install the Container Network Interface (CNI) (Calico, Flannel, Weave). Here we used Calico.
3. Certain actions need to be done on all the nodes
4. Certain actions need to be done on the control node only
5. Certain actions need to be done on the worker nodes only
6. Here you will see 2 scripts, one for the master node and the other for the worker nodes
7. Its best to configure static IP addresses for each of the nodes in your cluster

Here are the step by step instructions

Step 1: Decide where to install your kubernetes cluster (Public cloud (AWS, AZURE, GCP, Digital Ocean)) or VMs on your laptop etc

Step 2: Provision the VMS and ensure that the networking and firewalls are all configured correctly. The VMs should have at least 2CPUs and 2GB of RAM each. The more the better.

Step 3: Decide on your control node and ensure it has Ubuntu 20.04 or 22.04. Here I used Ubuntu 22.04.

Step 4: Login to the master/control node  and become root then run this script

###initialize the system####

sudo swapoff -a

sudo modprobe overlay

sudo modprobe br_netfilter

sudo sysctl -w net.bridge.bridge-nf-call-ip6tables = 1

sudo sysctl -w net.bridge.bridge-nf-call-iptables = 1

sudo sysctl -w net.ipv4.ip_forward=1

sudo sysctl --system

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

###INSTALL THE CONTAINER RUNTIME-containerd

sudo apt update

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

export OS_VERSION=xUbuntu_20.04

export CRIO_VERSION=1.23

curl -fsSL https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS_VERSION/Release.key | sudo gpg --dearmor -o /usr/share/keyrings/libcontainers-archive-keyring.gpg

curl -fsSL https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$CRIO_VERSION/$OS_VERSION/Release.key | sudo gpg --dearmor -o /usr/share/keyrings/libcontainers-crio-archive-keyring.gpg

echo "deb [signed-by=/usr/share/keyrings/libcontainers-archive-keyring.gpg] https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS_VERSION/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list

echo "deb [signed-by=/usr/share/keyrings/libcontainers-crio-archive-keyring.gpg] https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$CRIO_VERSION/$OS_VERSION/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$CRIO_VERSION.list

sudo apt update

sudo apt install -y cri-o cri-o-runc

sudo systemctl daemon-reload

sudo systemctl enable crio

sudo systemctl start crio

sudo apt install -y containernetworking-plugins

sudo systemctl restart crio

sudo apt install -y cri-tools

###INSTALL KUBERNETES

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 update

sudo apt install -y kubelet kubeadm kubectl

sudo apt-mark hold kubelet kubeadm kubectl

###Initialize the master node

sudo kubeadm init

###Configire the user profile

mkdir -p $HOME/.kube

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

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

kubectl get nodes

###Install the Calico CNI

curl https://projectcalico.docs.tigera.io/manifests/calico.yaml -O

kubectl apply -f calico.yaml

kubectl get pods -n kube-system

Step 5: Wait for the installation to complete successsfully. When all is done, it will spit out a script to use in joing the worker nodes. This will look like:

kubeadm join 192.168.1.147:6443 --token svygw2.vxl9qcg0yzrtqlaj \

--discovery-token-ca-cert-hash sha256:5c8840dfe8a72973790a2259b9838016d742e322f8241a10f97dbcdb3b15ffbe

Something should be wrong if you don't see this so you need to troubleshoot and fix the issue before proceeding.

Remember to keep this script securely stored somewhere because you will need it anytime you want to join a worker node to the master node.

Step 6. If all is well with the master node, you can now start to deploy the worker nodes and join them to the cluster. For each of the nodes, login, become root and run this script:

###initialize the system####

sudo swapoff -a

sudo modprobe overlay

sudo modprobe br_netfilter

sudo sysctl -w net.bridge.bridge-nf-call-ip6tables = 1

sudo sysctl -w net.bridge.bridge-nf-call-iptables = 1

sudo sysctl -w net.ipv4.ip_forward=1

sudo sysctl --system

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

###INSTALL THE CONTAINER RUNTIME-containerd

sudo apt update

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

export OS_VERSION=xUbuntu_20.04

export CRIO_VERSION=1.23

curl -fsSL https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS_VERSION/Release.key | sudo gpg --dearmor -o /usr/share/keyrings/libcontainers-archive-keyring.gpg

curl -fsSL https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$CRIO_VERSION/$OS_VERSION/Release.key | sudo gpg --dearmor -o /usr/share/keyrings/libcontainers-crio-archive-keyring.gpg

echo "deb [signed-by=/usr/share/keyrings/libcontainers-archive-keyring.gpg] https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/$OS_VERSION/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list

echo "deb [signed-by=/usr/share/keyrings/libcontainers-crio-archive-keyring.gpg] https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable:/cri-o:/$CRIO_VERSION/$OS_VERSION/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable:cri-o:$CRIO_VERSION.list

sudo apt update -y

sudo apt install -y cri-o cri-o-runc

sudo systemctl daemon-reload

sudo systemctl enable crio

sudo systemctl start crio

#sudo systemctl status crio

sudo apt install -y containernetworking-plugins

sudo systemctl restart crio

sudo apt install -y cri-tools

###INSTALL KUBERNETES

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

sudo apt-add-repository -y "deb http://apt.kubernetes.io/ kubernetes-xenial main"

sudo apt update -y

sudo apt install -y kubelet kubeadm kubectl

sudo apt-mark hold kubelet kubeadm kubectl

Step 7: Run the script you obtained from completing the master node

root@master-22-04:~# kubeadm join 192.168.1.147:6443 --token svygw2.vxl9qcg0yzrtqlaj \

--discovery-token-ca-cert-hash sha256:5c8840dfe8a72973790a2259b9838016d742e322f8241a10f97dbcdb3b15ffbe 

Step 8: Go to the master node and check that your cluster has all the nodes joined. Here is an example with the above scripts

root@master-22-04:~# kubectl get nodes -o wide

NAME              STATUS     ROLES           AGE     VERSION   INTERNAL-IP  EXTERNAL-IP   OS-IMAGE           KERNEL-VERSION      CONTAINER-RUNTIME

master-22-04        Ready      control-plane   22h     v1.24.3   192.168.1.147   none>        Ubuntu 22.04 LTS   5.15.0-41-generic   cri-o://1.23.3

master-22-04-crio   Ready      <none>          6h53m   v1.24.3   192.168.1.148  <none>        Ubuntu 22.04 LTS   5.15.0-41-generic   cri-o://1.23.3

Step 9: Enjoy your new cluster

Conclusion:

Here I have shown you how to deploy a kubernetes cluster with the following services

• Kubernetes version 1.24.3
• Ubuntu 22.04 LTS
• CRI-O Container Runtime Interface
• Calico Container Network Interface