500 Essential Ops Terms: Kubernetes, Docker & SRE Glossary

Part 1: Kubernetes Core Concepts

K8s / Kubernetes : Container orchestration platform

Master / Control Plane : Cluster control plane node

Node / Worker Node : Cluster worker node

Pod : Smallest deployable unit in K8s, contains one or more containers

Deployment : Stateless application controller, manages Pod replicas

StatefulSet : Stateful application controller, ensures Pod ordering and stability

DaemonSet : Controller that runs one Pod on each node

Job : One-time task controller

CronJob : Scheduled task controller

ReplicaSet : Replica count maintenance controller, managed by Deployment

Namespace : Virtual cluster for resource isolation

Label : Labels used for resource selection and organization

Selector : Selector, filters resources based on labels

Annotation : Annotations, attaches non-identifying metadata

Ingress : Layer 7 load balancing, manages external access

Service : Pod access policy, stable service exposure

ClusterIP : Default Service type, internal cluster access

NodePort : Service type, exposes via node port

LoadBalancer : Service type, integrates with cloud provider LB

Headless Service : Headless service (ClusterIP set to None), used for stateful services

Endpoint / Endpoints : List of Pod IPs associated with a Service

ConfigMap : Stores non-sensitive configuration data

Secret : Stores sensitive data (passwords, keys, etc.)

PV / PersistentVolume : Persistent volume, cluster-level storage resource

PVC / PersistentVolumeClaim : Persistent volume claim, requests storage resources

Part 2: Kubernetes Components and Networking

API Server / APIServer : K8s core management component, provides REST API

Scheduler : Scheduler, responsible for scheduling Pods to Nodes

Controller Manager : Controller manager, runs various controllers

Kubelet : Node agent, manages container lifecycle

Kube-proxy : Node network proxy, implements Service forwarding

Etcd : Distributed key-value store, stores all cluster data

CoreDNS : Cluster internal DNS resolution

CNI / ContainerNetworkInterface : Container Network Interface specification

Calico : CNI network plugin (supports BGP/IPIP/VXLAN)

Flannel : CNI network plugin (simple and easy to use)

Cilium : CNI network plugin (based on eBPF)

BGP / BorderGatewayProtocol : Border Gateway Protocol (Calico mode)

Part 3: Docker and Container Terminology

Docker : Container engine

Dockerfile : Script for building images

Image : Image / read-only template for containers

Container : Container / running instance of an image

Registry : Image registry / service for storing images (e.g., Harbor, Docker Hub)

Harbor : Enterprise-grade private image registry

Docker-compose : Multi-container orchestration tool (single-host)

Docker Swarm : Docker native cluster management (now marginalized)

Build Context : Build context / path specified during docker build