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Setting Up a Kubernetes Cluster with MetalLB on Bare Metal

In this guide, we’ll walk through setting up a Kubernetes cluster on two Ubuntu VPS servers and using MetalLB to provide LoadBalancer services. This setup is ideal for environments where you don’t have access to cloud-provided load balancers, such as bare-metal or on-premises deployments.

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What You’ll Need

• Two Ubuntu VPS servers with the following:
• Public IP addresses: 203.0.113.10 and 203.0.113.11.
• At least 2 GB RAM and 2 vCPUs per node.
• SSH access to both servers.
• Basic familiarity with Kubernetes and Linux commands.

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Step 1: Set Up the Kubernetes Cluster

1.1 Prepare the Nodes

On both servers:

1. Disable swap:

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

2. Install dependencies:

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

1.2 Install Kubernetes Tools

On both servers:

1. Add the Kubernetes repository:

   curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.29/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:/v1.29/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list
   sudo apt update

2. Install kubeadm, kubelet, and kubectl:

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

1.3 Initialize the Control Plane

On the master node (203.0.113.10):

sudo kubeadm init --pod-network-cidr=10.244.0.0/16

• Save the kubeadm join command for adding worker nodes.

Configure kubectl:

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

1.4 Join the Worker Node

On the worker node (203.0.113.11):

sudo kubeadm join <master-ip>:6443 --token <token> --discovery-token-ca-cert-hash <hash>

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Step 2: Install MetalLB for Load Balancing

2.1 Deploy MetalLB

MetalLB provides LoadBalancer services for bare-metal Kubernetes clusters. Deploy it using the following command:

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.13.12/config/manifests/metallb-native.yaml

2.2 Configure MetalLB

Create a configuration file (metallb-config.yaml) to define the IP address pool:

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: production-public-ips
  namespace: metallb-system
spec:
  addresses:
  - 203.0.113.10-203.0.113.11  # Use your two IPs here
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: l2-advert
  namespace: metallb-system
spec:
  ipAddressPools:
  - production-public-ips

Apply the configuration:

kubectl apply -f metallb-config.yaml

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Step 3: Test the Setup

3.1 Deploy a Test Application

Deploy an nginx application:

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=LoadBalancer

3.2 Verify the Service

Check the service status:

kubectl get svc nginx

Expected Output:

NAME    TYPE           CLUSTER-IP      EXTERNAL-IP       PORT(S)        AGE
nginx   LoadBalancer   10.96.123.45    203.0.113.10      80:30000/TCP   1m

3.3 Access the Application

Use the external IP to access the nginx service:

curl http://203.0.113.10

• You should see the default nginx welcome page.

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Step 4: High Availability and Scaling

4.1 Use Both IP Addresses

You can deploy additional services and assign the second IP (203.0.113.11) to them. For example:

kubectl create deployment nginx2 --image=nginx
kubectl expose deployment nginx2 --port=80 --type=LoadBalancer

4.2 Scale Applications

Scale your applications across both nodes:

kubectl scale deployment nginx --replicas=3
kubectl get pods -o wide

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Step 5: Firewall Rules

Ensure the following ports are open:

• MetalLB: 7946 (TCP/UDP) and 7472 (UDP).
• Kubernetes: 6443 (API server), 10250 (kubelet), and 30000-32767 (NodePort range).

Example ufw rules:

sudo ufw allow 7946/tcp
sudo ufw allow 7946/udp
sudo ufw allow 7472/udp
sudo ufw allow 6443/tcp
sudo ufw allow 10250/tcp
sudo ufw allow 30000:32767/tcp
sudo ufw reload

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Conclusion

With MetalLB, you can provide LoadBalancer services for your Kubernetes cluster even in bare-metal or on-premises environments. This setup is cost-effective and leverages your existing infrastructure. By following this guide, you’ve successfully:

1. Set up a Kubernetes cluster on two nodes.
2. Deployed MetalLB to manage external IPs.
3. Tested the setup with a sample application.

Feel free to explore advanced features like persistent storage, ingress controllers, or RBAC to enhance your cluster further.

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