kubectl Basics

Cluster Info

kubectl cluster-info
kubectl get nodes
kubectl config current-context
kubectl config use-context my-cluster

Essential Commands

kubectl get <resource>	List resources
kubectl describe <resource> <name>	Detailed resource info
kubectl create -f file.yaml	Create resource from file
kubectl apply -f file.yaml	Create or update resource
kubectl delete -f file.yaml	Delete resource from file
kubectl edit <resource> <name>	Edit resource in-place
kubectl api-resources	List all resource types

Output Formats

-o wide	Extra columns (IP, node)
-o yaml	Full YAML output
-o json	Full JSON output
-o jsonpath='{.spec}'	Extract specific fields
--sort-by=.metadata.name	Sort output by field

Pods

Pod Operations

kubectl get pods
kubectl get pods -A                  # all namespaces
kubectl run nginx --image=nginx      # quick pod
kubectl delete pod nginx

Pod YAML

apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels: { app: myapp }
spec:
  containers:
    - name: app
      image: nginx:1.27
      ports:
        - containerPort: 80

Pod Status Values

Running	All containers started
Pending	Waiting for scheduling or image pull
CrashLoopBackOff	Container keeps crashing and restarting
ImagePullBackOff	Cannot pull container image
Completed	Ran to completion (Jobs)

Deployments

Deployment YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 3
  selector:
    matchLabels: { app: web }
  template:
    metadata:
      labels: { app: web }
    spec:
      containers:
        - name: web
          image: nginx:1.27
          ports:
            - containerPort: 80

Deployment Commands

kubectl get deploy	List deployments
kubectl scale deploy web --replicas=5	Scale replicas
kubectl set image deploy/web web=nginx:1.28	Update image (rolling)
kubectl rollout status deploy/web	Watch rollout progress
kubectl rollout undo deploy/web	Rollback to previous revision
kubectl rollout history deploy/web	View revision history

Services

Service Types

ClusterIP	Internal only (default)
NodePort	Expose on each node's IP at a static port
LoadBalancer	External load balancer (cloud)
ExternalName	DNS alias to external service

Service YAML

apiVersion: v1
kind: Service
metadata:
  name: web-svc
spec:
  type: ClusterIP
  selector: { app: web }
  ports:
    - port: 80
      targetPort: 80

Quick Expose

kubectl expose deploy web --port=80 --type=ClusterIP
kubectl expose deploy web --port=80 --type=NodePort
kubectl get svc

ConfigMaps & Secrets

ConfigMap

kubectl create configmap app-cfg \
  --from-literal=DB_HOST=db.example.com \
  --from-file=config.ini

Secret

kubectl create secret generic db-creds \
  --from-literal=username=admin \
  --from-literal=password=s3cret

Using in Pods

# As environment variables
envFrom:
  - configMapRef: { name: app-cfg }
  - secretRef:    { name: db-creds }

# As volume mount
volumes:
  - name: cfg
    configMap: { name: app-cfg }

Commands

kubectl get cm	List ConfigMaps
kubectl get secret	List Secrets
kubectl describe cm app-cfg	Show ConfigMap data
kubectl get secret db-creds -o yaml	Show Secret (base64-encoded)

Namespaces

Namespace Commands

kubectl get ns	List namespaces
kubectl create ns staging	Create namespace
kubectl delete ns staging	Delete namespace and all resources
kubectl get pods -n staging	List pods in namespace
kubectl get pods -A	List pods across all namespaces

Set Default Namespace

kubectl config set-context --current \
  --namespace=staging

Volumes

PersistentVolumeClaim

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data-pvc
spec:
  accessModes: [ReadWriteOnce]
  resources:
    requests: { storage: 10Gi }

Mount in Pod

volumes:
  - name: data
    persistentVolumeClaim:
      claimName: data-pvc
containers:
  - volumeMounts:
      - name: data
        mountPath: /app/data

Volume Types

emptyDir	Temp dir, deleted with pod
hostPath	Mount host filesystem path
persistentVolumeClaim	Persistent storage (PVC)
configMap	Mount ConfigMap as files
secret	Mount Secret as files

Ingress

Ingress YAML

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: web-ingress
spec:
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: web-svc
                port: { number: 80 }

Ingress Notes

Ingress Controller	Required (nginx-ingress, traefik, etc.)
pathType: Prefix	Match URL prefix
pathType: Exact	Match exact URL path
TLS	Add `tls:` section with secret name

Debugging

Diagnostic Commands

kubectl logs <pod>	Container stdout/stderr
kubectl logs <pod> -c <ctr>	Specific container logs
kubectl logs <pod> --previous	Logs from crashed container
kubectl describe pod <pod>	Events, conditions, status
kubectl exec -it <pod> -- sh	Shell into container
kubectl port-forward <pod> 8080:80	Forward local port to pod
kubectl top pods	CPU/memory usage (metrics-server)
kubectl get events --sort-by=.lastTimestamp	Cluster events timeline

Debug Pod

kubectl run debug --rm -it --image=busybox -- sh
# or attach ephemeral container
kubectl debug -it  --image=busybox

Common Patterns

Labels & Selectors

kubectl get pods -l app=web
kubectl get pods -l 'env in (prod,staging)'
kubectl label pod myapp env=prod

Resource Limits

resources:
  requests: { cpu: 100m, memory: 128Mi }
  limits:   { cpu: 500m, memory: 256Mi }

Liveness & Readiness

livenessProbe:
  httpGet: { path: /healthz, port: 8080 }
  initialDelaySeconds: 5
  periodSeconds: 10
readinessProbe:
  httpGet: { path: /ready, port: 8080 }

Quick Recipes

Dry run	`kubectl apply -f file.yaml --dry-run=client`
Generate YAML	`kubectl create deploy web --image=nginx --dry-run=client -o yaml`
Watch	`kubectl get pods -w`
Copy files	`kubectl cp file.txt pod:/tmp/`
Restart deploy	`kubectl rollout restart deploy/web`

KUBERNETES QUICK REFERENCE