Kubernetes is a popular open-source platform for managing containerized workloads and services. It enables you to automate, scale, and orchestrate the deployment, configuration, and operation of your applications across multiple clusters of nodes. Kubernetes also provides features such as service discovery, load balancing, storage orchestration, self-healing, and secret management.
In this blog article, we will introduce some of the key concepts and components of Kubernetes, and show you how to install it on different operating systems.
What is Kubernetes?
Kubernetes is derived from the Greek word for “helmsman” or “pilot”. It was originally developed by Google as a project called Borg, which ran millions of containers in production for over a decade. In 2014, Google donated the project to the Cloud Native Computing Foundation (CNCF), which is a vendor-neutral organization that promotes the development and adoption of cloud-native technologies.
Kubernetes is based on the principle of declarative configuration, which means that you specify the desired state of your system using YAML or JSON files, and Kubernetes will take care of making it happen. You don’t need to worry about the details of how to create, update, or delete your resources; Kubernetes will handle that for you.
Kubernetes also follows the principle of modularity and extensibility, which means that you can customize and extend its functionality using various tools and plugins. For example, you can use different container runtimes (such as Docker or containerd), networking plugins (such as Calico or Flannel), storage plugins (such as NFS or GlusterFS), or service meshes (such as Istio or Linkerd).
What are the benefits of Kubernetes?
Kubernetes offers many benefits for developers and operators who want to run their applications in a reliable, scalable, and portable way. Some of the main benefits are:
- High availability: Kubernetes ensures that your applications are always up and running by automatically restarting failed containers, rescheduling them when nodes die, and replicating them across multiple nodes.
- Scalability: Kubernetes allows you to easily scale your applications up or down by adding or removing pods (the basic units of deployment in Kubernetes) based on demand or metrics. You can also use horizontal pod autoscaling (HPA) or vertical pod autoscaling (VPA) to automatically adjust the number or size of your pods.
- Load balancing: Kubernetes distributes the traffic among your pods using services (the logical abstractions of your applications) and ingress controllers (the components that expose your services to external clients). You can also use network policies to control the communication between your pods and services.
- Service discovery: Kubernetes assigns unique names and IP addresses to your pods and services, and maintains a DNS server that resolves them. You can also use labels and selectors to group and filter your resources based on various criteria.
- Storage orchestration: Kubernetes allows you to mount different types of storage volumes (such as local disks, network-attached storage, or cloud storage) to your pods, and dynamically provision them using persistent volume claims (PVCs) and storage classes.
- Self-healing: Kubernetes monitors the health of your pods and services using liveness probes and readiness probes, and takes corrective actions such as restarting, rescheduling, or replacing them if they are not healthy.
- Secret management: Kubernetes allows you to store and manage sensitive information such as passwords, tokens, or certificates using secrets, which are encrypted at rest and in transit. You can also use config maps to store and manage non-sensitive configuration data such as environment variables or files.
- Portability: Kubernetes runs on any platform that supports its minimum requirements, such as Linux, Windows, macOS, or cloud providers. You can also use tools such as Helm or Kustomize to package and deploy your applications across different environments.
What are the components of Kubernetes?
Kubernetes consists of two main types of components: master components and node components. Master components are responsible for managing the cluster state and coordinating the actions among the nodes. Node components are responsible for running the containers and providing the runtime environment for them.
The following diagram shows an overview of the Kubernetes architecture:
The master components include:
- API server: The API server is the central component that exposes the Kubernetes API, which is used by users, administrators, and other components to communicate with the cluster. The API server validates and processes the requests, and updates the cluster state accordingly.
- etcd: etcd is a distributed key-value store that stores the cluster data in a consistent and reliable way. It acts as the source of truth for the cluster state and configuration.
- Scheduler: The scheduler is responsible for assigning pods to nodes based on various factors such as resource availability, affinity/anti-affinity rules, taints/tolerations, etc. The scheduler watches for new pods that have no node assigned, and selects a suitable node for them.
- Controller manager: The controller manager is a collection of controllers that run in the background and perform various tasks such as replicating pods, updating endpoints, creating service accounts, etc. Each controller is a control loop that watches for changes in the cluster state, and tries to bring the current state closer to the desired state.
- Cloud controller manager: The cloud controller manager is an optional component that integrates Kubernetes with various cloud providers. It allows you to use cloud-specific features and resources such as load balancers, storage volumes, or networking routes.
The node components include:
- Kubelet: The kubelet is the agent that runs on each node and communicates with the API server. It manages the pods and containers on the node, and reports their status and metrics to the master. It also executes the instructions from the scheduler and the controller manager, such as creating, starting, stopping, or deleting pods and containers.
- Container runtime: The container runtime is the software that runs and manages the containers on the node. Kubernetes supports various container runtimes such as Docker, containerd, CRI-O, etc. The container runtime interacts with the kubelet through the container runtime interface (CRI).
- Kube-proxy: The kube-proxy is a network proxy that runs on each node and maintains the network rules and connections for the pods and services. It implements part of the Kubernetes service concept using iptables, ipvs, or other mechanisms.
- CNI plugins: The CNI plugins are responsible for providing the network connectivity for the pods on the node. Kubernetes supports various CNI plugins such as Calico, Flannel, Weave Net, etc. The CNI plugins interact with the kubelet through the container network interface (CNI).
How to install Kubernetes on different operating systems?
There are many ways to install Kubernetes on different operating systems, depending on your needs and preferences. You can use tools such as kubeadm, minikube, microk8s, kind, k3s, etc. to set up a single-node or multi-node cluster on your local machine or in a virtual environment. You can also use tools such as kops, kubespray, eksctl, gcloud, etc. to set up a cluster on a cloud provider or a bare-metal server.
In this section, we will show you how to install Kubernetes using kubeadm on Linux, minikube on macOS, and Docker Desktop on Windows.
How to install Kubernetes using kubeadm on Linux?
kubeadm is a tool that helps you bootstrap a Kubernetes cluster using best practices. It requires you to have a container runtime and a CNI plugin installed on your nodes. It also requires you to have at least one master node and one or more worker nodes.
The following steps will guide you through installing Kubernetes using kubeadm on Linux:
- Install Docker as the container runtime on each node. You can follow the official instructions for your Linux distribution [here]
- Install kubeadm, kubelet, and kubectl on each node. You can follow the official instructions for your Linux distribution [here]
- Initialize the cluster on the master node using kubeadm init command. You can specify various options such as pod network CIDR, control plane endpoint, API server advertise address, etc. For example:
This command will generate a join token and a certificate key that you will need to join the worker nodes to the cluster later.
- Set up the kubeconfig file for your user account on the master node using the following commands:
- Install a CNI plugin of your choice on the master node. You can choose from various CNI plugins such as Calico, Flannel, Weave Net, etc. For example, to install Calico, you can run:
- Join the worker nodes to the cluster using kubeadm join command with the token and certificate key generated by kubeadm init command earlier. For example:
- Verify that all nodes are ready and joined to the cluster using kubectl get nodes command on the master node:
- You can now start deploying your applications on the cluster using kubectl or other tools. You can also use kubeadm to upgrade, reset, or remove nodes from the cluster. For more details, you can refer to the official documentation [here].
How to install Kubernetes using minikube on macOS?
minikube is a tool that helps you run a single-node Kubernetes cluster on your local machine. It supports various drivers such as virtualbox, hyperkit, docker, etc. to create and manage the cluster. It also provides features such as addons, profiles, dashboard, etc. to enhance your experience.
The following steps will guide you through installing Kubernetes using minikube on macOS:
- Install Homebrew if you don’t have it already. You can follow the official instructions [here].
- Install Docker as the container runtime on your machine. You can follow the official instructions [here].
- Install minikube using Homebrew:
- Start the cluster using minikube start command. You can specify various options such as driver, memory, cpu, kubernetes version, etc. For example:
This command will download the required images and binaries, and create a virtual machine with Kubernetes running on it.
- Set up the kubeconfig file for your user account using the following command:
- Verify that the cluster is running and ready using minikube status command:
- You can now start deploying your applications on the cluster using kubectl or other tools. You can also use minikube to stop, delete, or restart the cluster. If you are stuck, please feel free to leave a comment below or contact us at [email protected]. We will help you.
How to install Kubernetes using Docker Desktop on Windows?
Docker Desktop is a tool that helps you run Docker and Kubernetes on your Windows machine. It provides an easy-to-use graphical interface and a command-line tool to manage your containers and clusters. It also integrates with other tools such as Visual Studio Code, Helm, etc.
The following steps will guide you through installing Kubernetes using Docker Desktop on Windows:
- Install Docker Desktop if you don’t have it already. You can follow the official instructions [here].
- Open Docker Desktop and go to Settings > Kubernetes.
- Check the box “Enable Kubernetes” and click “Apply & Restart”.
- Wait for a few minutes until Docker Desktop downloads the required images and binaries, and creates a single-node Kubernetes cluster on your machine.
- Verify that the cluster is running and ready using docker desktop status command in PowerShell:
- Set up the kubeconfig file for your user account using the following command:
- You can now start deploying your applications on the cluster using kubectl or other tools. You can also use Docker Desktop to stop, start, or reset the cluster. For more details, you can refer to the official documentation [here].
In this blog article, we have introduced some of the key concepts and components of Kubernetes, and showed you how to install it on different operating systems using kubeadm, minikube, and Docker Desktop. We hope that this article has helped you understand the basics of Kubernetes and how to get started with it.
But this merely scratches the surface of Kubernetes. It’s a robust and complex platform that offers many advanced features. Ready to dive deeper into Kubernetes? Join our advanced Devops Architect training course in which you can explore more advanced topics and concepts and tackle real-world challenges . . Here are some advanced Kubernetes terms and topics to consider: