Kubernetes

Sefism.Kubernetes

Tauseef Fayyaz

A to Z

Glossary

Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.

A

API server: The front door of the cluster. kubectl, controllers, kubelets and CI all read and write objects through its REST API, which authenticates, authorises and validates every request.
apply, diff and dry runs: kubectl apply -f creates or updates objects to match files.

C

Container runtime, kube-proxy and CNI: The runtime (usually containerd, through the CRI) runs containers.

D

Desired state and reconciliation: You declare objects (a Deployment with three replicas) and controllers loop forever, comparing the declared spec with the observed status and acting to close the gap.

E

etcd: A consistent, distributed key-value store holding every object in the cluster.

G

get and describe: kubectl get lists objects in a table, or full YAML with -o yaml.

K

kubeconfig and contexts: kubeconfig (~/.kube/config or $KUBECONFIG) lists clusters, users and contexts.
kubectl explain: Prints the schema and documentation for any field of any resource, straight from the cluster's API.
kubelet: The agent on every node.

L

Labels and selectors: Labels are key and value pairs on objects, like app: api.

M

Managed clusters: Cloud services run and upgrade the control plane for you; you manage node pools (or let the provider manage them too) and your workloads. kind, k3d and minikube run small clusters locally.
Manifest anatomy: Every object has apiVersion, kind, metadata (name, namespace, labels, annotations) and usually spec (what you want).

O

Output formats and jsonpath: -o yaml and -o json print full objects, -o wide adds columns, and -o jsonpath or custom-columns extract exactly the fields you want.

S

Scheduler and controller manager: The scheduler assigns each new Pod to a node that fits its resource requests and constraints.