Kubernetes Cheatsheet

Deployments Reference

Use this Kubernetes reference while you build software engineering projects, review code for technical interview prep, or polish examples for a software engineer resume.

Deployment Manifest

apiVersion: apps/v1
kind: Deployment
metadata:
  name: api
  namespace: production
spec:
  replicas: 3
  selector:
    matchLabels:
      app: api              # must match template labels
  template:
    metadata:
      labels:
        app: api
        version: "2.1"
    spec:
      containers:
      - name: api
        image: myrepo/api:2.1
        ports:
        - containerPort: 8080
        resources:
          requests:
            cpu: "250m"
            memory: "256Mi"
          limits:
            cpu: "1"
            memory: "512Mi"

Rollout Strategy

RollingUpdate (default)

spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1     # or "25%"
      maxSurge: 1           # or "25%"

New Pods come up before old ones go down (zero-downtime).
maxUnavailable: how many Pods can be down at once.
maxSurge: how many extra Pods can exist above replicas.

Recreate

spec:
  strategy:
    type: Recreate          # terminate all old Pods, then create new ones

Use when old and new versions cannot run simultaneously (DB schema breaks backward compat).

kubectl Deployment Commands

Command	What it does
`kubectl apply -f deploy.yaml`	Create or update deployment
`kubectl get deployments`	List deployments
`kubectl describe deployment api`	Events, replica counts, conditions
`kubectl rollout status deployment/api`	Watch rollout progress
`kubectl rollout history deployment/api`	Show revision history
`kubectl rollout undo deployment/api`	Roll back to previous revision
`kubectl rollout undo deployment/api --to-revision=3`	Roll back to revision 3
`kubectl rollout restart deployment/api`	Rolling restart (re-pull image)
`kubectl scale deployment api --replicas=5`	Scale manually
`kubectl set image deployment/api api=myrepo/api:2.2`	Update image
`kubectl delete deployment api`	Delete deployment + pods

Image Update and Rollback

# update image (triggers rolling update)
kubectl set image deployment/api api=myrepo/api:2.2

# annotate so rollout history is readable
kubectl annotate deployment/api kubernetes.io/change-cause="release v2.2"

# check history
kubectl rollout history deployment/api

# undo
kubectl rollout undo deployment/api

# undo to specific revision
kubectl rollout undo deployment/api --to-revision=2

# pause / resume a rollout
kubectl rollout pause deployment/api
kubectl rollout resume deployment/api

Deployment Conditions

Condition	Meaning
`Available`	≥ minReadySeconds after last container restart
`Progressing`	New ReplicaSet scaling up or old one scaling down
`ReplicaFailure`	ReplicaSet failed to create a Pod

kubectl get deployment api -o jsonpath='{.status.conditions[*].type}'

Pod Disruption Budget

Prevent too many replicas going down during voluntary disruptions (drains, upgrades):

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: api-pdb
spec:
  minAvailable: 2         # or maxUnavailable: 1
  selector:
    matchLabels:
      app: api

StatefulSet vs. Deployment

Feature	Deployment	StatefulSet
Pod identity	Random suffix	Stable (`app-0`, `app-1`)
Start/stop order	Parallel	Ordered (0 → n / n → 0)
Storage	Shared or ephemeral	Per-Pod PVC (`volumeClaimTemplates`)
Use case	Stateless apps	DBs, queues, Zookeeper

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: postgres
spec:
  serviceName: postgres     # headless Service required
  replicas: 3
  selector:
    matchLabels:
      app: postgres
  template:
    metadata:
      labels:
        app: postgres
    spec:
      containers:
      - name: postgres
        image: postgres:16
        volumeMounts:
        - name: data
          mountPath: /var/lib/postgresql/data
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 10Gi

DaemonSet

Runs exactly one Pod per (matching) Node:

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: node-exporter
spec:
  selector:
    matchLabels:
      app: node-exporter
  template:
    metadata:
      labels:
        app: node-exporter
    spec:
      containers:
      - name: exporter
        image: prom/node-exporter:latest
        ports:
        - containerPort: 9100
      tolerations:
      - operator: Exists   # run on control-plane nodes too