Kubernetes Terminology
This blog will help folks those who all are passionate about learning Kubernetes, Below are the terms which are being used frequently when we start using the Kubernetes.
API Server: Part of the K8s control plane and runs on Masters. All communication with Kubernetes goes through the API Server. kubectl commands and responses go through the API Server.
Container: An application packaged to run on Docker or Kubernetes. As
well as an application, every container is a virtual operating
system with its own process tree, filesystem, shared memory,
and more.
Cloud-native: This is a loaded term and means different things to different
people. I personally consider an application to be cloud-native if
it can self-heal, scale on-demand, perform rolling updates and
rollbacks. They’re usually microservices apps and run on
Kubernetes.
Container runtime: Low-level software running on every cluster Node responsible for pulling container images, and starting and stopping
containers. The most famous container runtime is Docker, however, containerd is becoming the most popular container runtime used by Kubernetes.
Controller : Control plane process running as a reconciliation loop
monitoring the cluster and making the necessary changes so the
observed state of the cluster matches desired state.
Cluster store: Control plane feature that holds the state of the cluster and apps.
Deployment: Controller that deploys and manages a set of stateless Pods.
Performs rolling updates and rollbacks, and can self-heal.
Desired state: What the cluster and apps should be like. For example, the desired state of an application microservice might be 5 replicas of xyz container listening on port 8080/tcp.
K8s: Shorthand way to write Kubernetes. The 8 replaces the eight
characters in Kubernetes between the “K” and the “s”.
Pronounced “Kates”. The reason why people say Kubernetes’
girlfriend is called Kate.
kubectl: Kubernetes command line tool. Sends commands to the API Server and queries state via the API Server.
Kubelet: The main Kubernetes agent running on every cluster Node. It
watches the API Server for new work assignments and
maintains a reporting channel back.
Label: Metadata applied to objects for grouping. For example, Services
send traffic to Pods based on matching labels.
Manifest file: YAML file that holds the configuration of one or more
Kubernetes objects. For example, a Service manifest file is typically a YAML file that holds the configuration of a Service object. When you post a manifest file to the API Server, its configuration is deployed to the cluster.
Master: Cluster node running control plane services. The brains of a
Kubernetes cluster. You should deploy 3 or 5 for high availability.
Microservices: A design pattern for modern applications. Application features are broken into their own small applications (microservices/containers) and communicate via APIs. They work together to form a useful application.
Node: Also known as worker node. The nodes in a cluster that run user
applications. Must run the kubelet process and a container
runtime.
Observed state: Also known as current state or actual state. The most up-to-date view of the cluster and running applications.
Orchestrator: A piece of software that deploys and manages microservices
apps. Kubernetes is the de facto orchestrator of microservices
apps based on containers.
Pod: A thin wrapper that enables containers to run on Kubernetes. Defined in a YAML file.
Reconciliation loop: A controller process watching the state of the cluster, via the API Server, ensuring observed state matches desired state. The
Deployment controller runs as a reconciliation loop.
Service : Capital “S”. Kubernetes object for providing network access to
apps running in Pods. Can integrate with cloud platforms and
provision internet-facing load-balancers.
YAML: Yet Another Markup Language. The configuration language
Kubernetes configuration files are written in.
Thanks for reading…
