Kubernetes is an orchestration solution to manage clusters of cloud services. Also called micro-services.

Big Picture

A Kubernetes cluster consist of a control plane which holds all the processes that manage, orchestrate and schedule nodes. When you use a cloud provider’s K9s service, you use your kubectl command to connect to their hosted control plane.

Hint: https://github.com/ahmetb/kubectx is a great for switching namespaces and clusters through the terminal.

Components

• kubelet - The primary agent that runs on each node. The kubelet takes a set of PodSpecs and ensures that the described containers are running and healthy.
• kube-apiserver - REST API that validates and configures data for API objects such as pods, services, replication controllers.
• kube-controller-manager - Daemon that embeds the core control loops shipped with Kubernetes.
• kube-proxy - Can do simple TCP/UDP stream forwarding or round-robin TCP/UDP forwarding across a set of back-ends.
• kube-scheduler - Scheduler that manages availability, performance, and capacity.
  • Scheduler Policies
  • Scheduler Profiles
• List of ports and protocols that should be open on control plane and worker nodes

API-Resources

Kubernetes has a list of resources that can be used when running a cluster. For example, secrets for storing keys.

To list all available resources:

$ kubectl api-resources

You can call get or describe to get more information about each resource for a cluster and namespace.

$ kubectl describe secretes
$ kubectl get configmap

Under the hood, these API resources are all defined as protobuf files.

Pods