Unlocking Kubernetes Mastery with Kubeadm and Calico

Welcome to the world of Kubernetes, often referred to as k8s, where containerized applications meet orchestration excellence. In this guide, we'll embark on a journey to master Kubernetes using Kubeadm and Calico, ensuring your containerized applications thrive in a dynamic and scalable environment.

Prerequisites:

Before we dive into the exciting world of Kubernetes, make sure you have the following prerequisites in place:

Hardware Requirements:

Prepare for Kubernetes mastery by ensuring you have a minimum of two nodes. Each node should meet these hardware specs:

• Minimum of 2GB of RAM

• Minimum of 2 CPU cores

Software Requirements:

Your chosen nodes should be running a Linux distribution that plays well with Kubernetes. For our journey, we recommend Ubuntu 20.04. Additionally, you'll need to equip each node with Docker.

Network Requirements:

Ensure your nodes can communicate seamlessly with each other over a network. A reliable network connection between the nodes is crucial for a successful Kubernetes journey.

Installation of Kubeadm and Calico: Step By Step

Step 1: Setting the Stage with Hostnames

Let's begin by configuring hostnames to ensure smooth communication between nodes. Open the /etc/hosts file on each node using the following command:

sudo nano /etc/hosts

This opens the file in the nano text editor. Append the following lines to the end of the file, replacing the IP addresses with your node's IP addresses:

10.0.0.2        master-node
10.0.0.3        worker-node1
10.0.0.4        worker-node2

Save and close the file.

Step 2: Skipping Swap Memory Tweaks

If you're running your Kubernetes cluster on a cloud VM service like a pro, you can skip this step. Kubernetes will work harmoniously with the memory configurations provided by your cloud provider.

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

Step 3: Crafting the IPV4 Bridge on All Nodes

To establish the IPV4 bridge across all nodes, execute the following commands on each node:

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

sudo modprobe overlay
sudo modprobe br_netfilter

# Sysctl parameters required by the setup; these persist through reboots
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables  = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward                 = 1
EOF

# Apply sysctl parameters without reboot
sudo sysctl --system

These commands set up the necessary network bridge and kernel parameters, orchestrating Kubernetes in harmony.

Step 4: Updating the Repository and Securing Required Packages

Prepare your nodes by updating the package repository and securing essential packages with these commands:

sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl

Step 5: Grasping the Google Cloud Public Signing Key

Secure the Google Cloud public signing key with these commands:

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

Step 6: Adding the Kubernetes APT Repository

Add the Kubernetes APT repository with this command:

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

Step 7: Revving Up the Repo & Deploying kubelet, kubeadm, kubectl, and docker.io

Prepare to deploy Kubernetes and Docker on all nodes with these commands:

sudo apt-get update
sudo apt install -y kubelet=1.28.1-1.1 kubeadm=1.28.1-1.1 kubectl=1.28.1-1.1 docker.io
sudo apt-mark hold kubelet kubeadm kubectl docker.io

This crafts the right environment and ensures that Kubernetes packages remain stable.

Step 8: Orchestrating Containerd Configurations on All Nodes

Create a containerd directory and configure container runtime settings with these commands:

sudo mkdir /etc/containerd
sudo sh -c "containerd config default > /etc/containerd/config.toml"

Now, it's time for some fine-tuning. Edit the config.toml file and locate the entry setting SystemdCgroup to false. Switch it to true, save the file, and restart containerd with these commands:

sudo sed -i 's/            SystemdCgroup = false/            SystemdCgroup = true/' /etc/containerd/config.toml
sudo systemctl restart containerd.service
sudo systemctl restart kubelet.service
sudo systemctl enable kubelet.service

Note that these commands must be executed as root on all nodes in your Kubernetes orchestra.

Step 9: Initiating Kubeadm Magic

On the master node, invoke the magic wand to initialize the Kubernetes control plane:

sudo kubeadm init --pod-network-cidr=10.10.0.0/16

Step 10: Copying Configuration to User's Realm

On the master node, transfer the configuration to the user's realm with these commands:

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

This sets the stage for user interaction with the Kubernetes cluster.

Step 11: Crafting the Calico Network

After the Kubeadm initiation, it's time to weave the Calico network for seamless pod-to-pod communication. Execute these commands on the master node:

kubectl create -f https://raw.githubusercontent.com/projectcalico/calico/v3.26.1/manifests/tigera-operator.yaml
curl https://raw.githubusercontent.com/projectcalico/calico/v3.26.1/manifests/custom-resources.yaml -O
sed -i 's/cidr: 192\.168\.0\.0\/16/cidr: 10.10.0.0\/16/g' custom-resources.yaml
kubectl create -f custom-resources.yaml

Step 12: Welcoming Worker Nodes

With the master node all set, it's time to welcome the worker nodes into the Kubernetes party. During the Kubeadm initialization on the master node, you'll receive a token to invite worker nodes: