Core Objects

First PublishedFeb 16, 2026ByAtif Alam

Kubernetes manages everything as objects — records of intent stored in etcd. You create them with YAML manifests and kubectl apply.

Pods

The smallest deployable unit. A pod wraps one or more containers that share:

• A network namespace (same IP, can talk via localhost).
• Storage volumes (shared directories).

You rarely create pods directly; you use a Deployment or other controller.

apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
    - name: app
      image: nginx:1.25
      ports:
        - containerPort: 80

ReplicaSets

Ensures a specified number of pod replicas are running at all times. If a pod dies, the ReplicaSet creates a new one.

You almost never create a ReplicaSet directly — Deployments manage them for you.

Deployments

The most common way to run stateless workloads. A Deployment manages a ReplicaSet and provides:

• Rolling updates — replace pods gradually, zero downtime.
• Rollbacks — revert to a previous version if something breaks.
• Scaling — change the number of replicas.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: app
          image: nginx:1.25
          ports:
            - containerPort: 80

Namespaces

Virtual partitions inside a cluster. Use them to isolate teams, environments, or projects.

• default — where objects go if you don’t specify a namespace.
• kube-system — Kubernetes system components.
• kube-public — readable by everyone (rarely used directly).

kubectl get namespaces
kubectl create namespace staging
kubectl get pods -n staging

Labels and Selectors

Labels are key-value pairs attached to objects. Selectors filter objects by their labels.

metadata:
  labels:
    app: my-app
    env: production

Selectors are how Services find pods, how Deployments manage ReplicaSets, and how you query with kubectl:

kubectl get pods -l app=my-app
kubectl get pods -l env=production

YAML Anatomy

Every Kubernetes resource is defined in a manifest with four top-level fields: apiVersion, kind, metadata, and spec. For full details on manifest structure, multi-resource files, spec vs status, and how to apply them, see Manifests.