Kubernetes Clusters
Users expect applications to be available 24/7, and developers expect to deploy new versions of those applications several times a day. Containerization helps package software to serve these goals, enabling applications to be released and updated without downtime. Kubernetes is used to containerized applications run where and when you want, and helps them find the resources and tools they need to work.
A Kubernetes cluster is a set of node machines for running containerized applications. If you’re running Kubernetes, you’re running a cluster.
At a minimum, a cluster contains a control plane and one or more compute machines, or nodes. The control plane is responsible for maintaining the desired state of the cluster, such as which applications are running and which container images they use. Nodes actually run the applications and workloads.
The cluster is the heart of Kubernetes’ key advantage: the ability to schedule and run containers across a group of machines, be they physical or virtual, on premises or in the cloud.
Control plane: The collection of processes that control Kubernetes nodes. This is where all task assignments originate.
Nodes: These machines perform the requested tasks assigned by the control plane.
Pod: A set of 1 or more containers deployed to a single node. A pod is the smallest and simplest Kubernetes object.
Service: A way to expose an application running on a set of pods as a network service. This decouples work definitions from the pods.
Volume: A directory containing data, accessible to the containers in a pod. A Kubernetes volume has the same lifetime as the pod that encloses it. A volume outlives any containers that run within the pod, and data is preserved when a container restarts.
Namespace: A virtual cluster. Namespaces allow Kubernetes to manage multiple clusters (for multiple teams or projects) within the same physical cluster.
A Kubernetes cluster can be deployed on either physical or virtual machines. To get started with Kubernetes development, you can use Minikube. Minikube is a lightweight Kubernetes implementation that creates a VM on your local machine and deploys a simple cluster containing only one node.
