Topic 01: Pods Link to heading

A Pod is the smallest deployable unit in Kubernetes. You don’t deploy containers directly — you deploy Pods that contain containers. Containers in the same Pod share a network namespace (same IP, same localhost) and can share volumes. Usually one container per Pod — multiple containers is the sidecar pattern.

Pods are ephemeral. If a Pod dies, a controller replaces it — it’s not restarted in place.

YAML Link to heading

apiVersion: v1
kind: Pod
metadata:
  name: web
  labels:
    app: web
    tier: frontend
spec:
  containers:
  - name: web # container name — cannot be set imperatively
    image: nginx
    ports:
    - containerPort: 80
    resources:
      requests:
        cpu: 100m
        memory: 64Mi
      limits:
        cpu: 200m
        memory: 128Mi

Common Patterns Link to heading

Command and args Link to heading

spec:
  containers:
  - name: runner
    image: busybox
    command: ["sh", "-c", "echo hello && sleep 3600"]

command overrides Docker ENTRYPOINT. args overrides Docker CMD. Both together override both.

Environment variables Link to heading

spec:
  containers:
  - name: app
    image: nginx
    env:
    - name: PORT
      value: "8080" # numeric values must be quoted
    - name: DEBUG
      value: "true"

Volume mount Link to heading

spec:
  containers:
  - name: app
    image: nginx
    volumeMounts:
    - name: data
      mountPath: /data
  volumes:
  - name: data
    emptyDir: {}

Imperative Link to heading

# Basic
k run web --image=nginx

# With labels
k run web --image=nginx --labels=app=web,tier=frontend

# With env vars
k run web --image=nginx --env=PORT=8080 --env=DEBUG=true

# With port
k run web --image=nginx --port=80

# In namespace
k run web --image=nginx -n production

# Generate YAML
k run web --image=nginx $do

# Force delete
k delete pod web --force --grace-period 0

# Exec into pod
k exec -it web -- sh
k exec -it web -c nginx -- sh # specific container in multi-container pod

# Logs
k logs web
k logs web -c nginx # specific container
k logs web --previous # crashed container
k logs web -f # follow

# Resource usage
k top pods
k top pod web

Common Mistakes Link to heading

  • Numeric env values not quoted — value: "8080" not value: 8080
  • containerPort is informational only — it doesn’t open or expose the port
  • Cannot name a container imperatively — container name defaults to pod name. Use $do and edit YAML if a specific container name is required.

Exam Tips Link to heading

  • k describe pod <n> → Events section shows scheduling or image pull failures
  • k get pod <n> -o wide → shows node and pod IP
  • k get pods --show-labels → always run before writing a NetworkPolicy
  • Pod lifecycle: Pending → Running → Succeeded / Failed
  • restartPolicy defaults to Always — Jobs require Never or OnFailure