Install and Configure Kubernetes on Ubuntu/Debian and CentOS/RHEL
Kubernetes has emerged as the leading open-source platform for container orchestration, streamlining the deployment, scaling, and overall management of containerized applications. This comprehensive guide provides a step-by-step walkthrough of installing Kubernetes on both Ubuntu/Debian and CentOS/RHEL operating systems. We’ll leverage essential tools like kubeadm, kubectl, and kubelet to establish a fully functional Kubernetes cluster.
Prerequisites
Before embarking on the installation journey, ensure the following prerequisites are met:
- A minimum of two machines: one designated as the master node and one or more as worker nodes.
- Each machine should have at least 2 GB of RAM and 2 CPUs.
- A stable network connection between all machines.
- Docker or another compatible container runtime installed on all machines.
- Root privileges or
sudoaccess on all machines.
Installing Kubernetes on Ubuntu/Debian
Step 1: Update Your System
Begin by updating your system packages to the latest versions:
$ sudo apt update && sudo apt upgrade -yStep 2: Install Docker
Kubernetes relies on a container runtime to manage containers. We’ll use Docker in this guide. You can follow this article to learn how to install and use Docker on Ubuntu LTS. Once Docker is installed, return to this guide to continue with the Kubernetes installation process.
Step 3: Disable Swap
For optimal performance, Kubernetes requires swap to be disabled:
$ sudo swapoff -a
$ sudo sed -i '/ swap / s/^/#/' /etc/fstabStep 4: Install Kubernetes Components
Install the required Kubernetes components: kubelet, kubeadm, and kubectl:
$ sudo apt install -y kubelet kubeadm kubectl
$ sudo systemctl enable kubeletStep 5: Initialize Kubernetes with kubeadm
Initialize Kubernetes on the master node using kubeadm. Replace <your-pod-network-cidr> with your desired Pod network CIDR (e.g., 192.168.0.0/16):
$ sudo kubeadm init --pod-network-cidr=<your-pod-network-cidr>Step 6: Set Up Kubectl
Configure kubectl to interact with your Kubernetes cluster:
$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/configStep 7: Configure Pod Network
Install a Pod network add-on. We’ll use Calico in this example:
$ kubectl apply -f https://docs.projectcalico.org/manifests/calico.yamlStep 8: Join Worker Nodes (Optional)
Join worker nodes to the cluster using the kubeadm join command displayed during master initialization. This command will look similar to this:
kubeadm join <master-ip>:<port> --token <token> --discovery-token-ca-cert-hash sha256:<hash>Installing Kubernetes on CentOS/RHEL
Step 1: Update Your System
Ensure your system is up-to-date:
$ sudo yum update -yStep 2: Install Docker
Install Docker, the container runtime for Kubernetes:
$ sudo yum install docker -y
$ sudo systemctl enable docker
$ sudo systemctl start dockerStep 3: Disable Swap
Disable swap to improve Kubernetes performance:
$ sudo swapoff -a
$ sudo sed -i '/ swap / s/^/#/' /etc/fstabStep 4: Install Kubernetes Components
Install kubeadm, kubectl, and kubelet:
$ sudo tee /etc/yum.repos.d/kubernetes.repo <<EOF
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF
$ sudo yum install -y kubelet kubeadm kubectl
$ sudo systemctl enable kubeletStep 5: Initialize Kubernetes with kubeadm
Initialize Kubernetes on the master node, specifying your Pod network CIDR:
$ sudo kubeadm init --pod-network-cidr=<your-pod-network-cidr>Step 6: Set Up Kubectl
Configure kubectl for your user:
$ mkdir -p $HOME/.kube
$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
$ sudo chown $(id -u):$(id -g) $HOME/.kube/configStep 7: Configure Pod Network
Deploy a Pod network add-on, such as Calico:
$ kubectl apply -f https://docs.projectcalico.org/manifests/calico.yamlStep 8: Join Worker Nodes (Optional)
Add worker nodes to the cluster using the kubeadm join command obtained during master initialization. The command will be similar to what was shown for Ubuntu/Debian.
Alternative Solutions for Kubernetes Installation
While kubeadm offers a straightforward approach to Kubernetes installation, alternative solutions provide different levels of abstraction and flexibility. Here are two alternatives:
1. Using Minikube:
Minikube is a lightweight Kubernetes distribution designed for local development and testing. It creates a single-node Kubernetes cluster within a virtual machine on your local machine. This approach simplifies the installation process, especially for developers who want to experiment with Kubernetes without setting up a full-fledged cluster.
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Explanation: Minikube abstracts away much of the complexity of manual Kubernetes installation. It handles the installation of the Kubernetes components, container runtime, and networking configuration. It’s ideal for quickly setting up a development environment.
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Installation Example (Ubuntu/Debian):
First install a hypervisor like KVM2 or VirtualBox. Then install minikube.
curl -Lo minikube https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64 chmod +x minikube sudo mv minikube /usr/local/bin/ minikube start --driver=kvm2This will download and install Minikube, start a Kubernetes cluster using KVM2 as the driver. You can then interact with the cluster using
kubectl. -
Advantages: Very easy to install and use, ideal for local development, requires minimal resources.
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Disadvantages: Limited to a single node, not suitable for production environments.
2. Using Rancher Kubernetes Engine (RKE):
RKE is a CNCF-certified Kubernetes distribution that runs entirely within Docker containers. It allows you to provision Kubernetes clusters on bare metal, virtual machines, or cloud providers. RKE automates the installation and configuration of Kubernetes components, providing a more flexible and customizable solution compared to kubeadm.
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Explanation: RKE uses a declarative configuration file to define the desired state of the Kubernetes cluster. It then uses Docker containers to deploy and manage the Kubernetes components. This approach allows for greater control over the cluster configuration and simplifies cluster upgrades.
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Installation Example:
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Install Docker: Ensure Docker is installed on all nodes in the cluster.
-
Download RKE CLI: Download the RKE CLI tool on your local machine.
curl -O https://github.com/rancher/rke/releases/download/v1.4.6/rke_linux-amd64 chmod +x rke_linux-amd64 sudo mv rke_linux-amd64 /usr/local/bin/rke -
Create a Cluster Configuration File (cluster.yml):
nodes: - address: <node1-ip> user: ubuntu role: [controlplane,worker,etcd] - address: <node2-ip> user: ubuntu role: [worker] - address: <node3-ip> user: ubuntu role: [worker] services: etcd: snapshot: true creation: 12h retention: 72h system_images: etcd: rancher/mirrored-coreos-etcd:v3.5.5Replace
<node1-ip>,<node2-ip>, and<node3-ip>with the IP addresses of your nodes. Adjust theuserandrolesettings as needed. -
Provision the Cluster:
rke up --config cluster.ymlRKE will then connect to the nodes and provision the Kubernetes cluster based on the configuration file.
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Advantages: Flexible and customizable, supports various infrastructure providers, simplifies cluster upgrades, built to be secure.
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Disadvantages: More complex than
kubeadmor Minikube, requires a deeper understanding of Kubernetes concepts.
Conclusion
This guide has covered the installation of Kubernetes on Ubuntu/Debian and CentOS/RHEL using kubeadm. We have also explored two alternative solutions: Minikube and RKE. Choosing the right approach depends on your specific needs and experience level. kubeadm provides a solid foundation for learning and deploying Kubernetes, while Minikube is ideal for local development. RKE offers greater flexibility and control for production deployments. Remember to secure your cluster and explore Kubernetes features to maximize its potential.