Kubectl

Website: https://kubernetes.io CLI Tool: kubectl Authentication: kubectl config use-context

Description

kubectl is the Kubernetes command-line tool for controlling Kubernetes clusters. It communicates with the Kubernetes API server to deploy applications, inspect and manage cluster resources, and view logs. Essential for container orchestration and cloud-native application management.

Commands

Cluster Information

Cluster Info

kubectl cluster-info
kubectl cluster-info dump

Display cluster endpoint information. Use dump for detailed cluster state.

Version

kubectl version
kubectl version --short

Show client and server Kubernetes versions.

Context Management

kubectl config get-contexts
kubectl config current-context
kubectl config use-context <context-name>
kubectl config set-context <context-name> --namespace=<namespace>

Manage kubectl contexts for multiple clusters.

Resource Management

Get Resources

kubectl get <resource>
kubectl get pods
kubectl get pods -o wide
kubectl get pods -o yaml
kubectl get pods -o json
kubectl get pods --all-namespaces
kubectl get pods -n <namespace>
kubectl get pods -l app=myapp
kubectl get all

List resources. Use -o for output format, -n for namespace, -l for label selector, --all-namespaces for all namespaces.

Describe Resources

kubectl describe <resource> <name>
kubectl describe pod myapp-pod
kubectl describe node node-1
kubectl describe service myapp-service

Show detailed information about a resource.

Create Resources

kubectl create -f <file>
kubectl create -f deployment.yaml
kubectl create deployment nginx --image=nginx
kubectl create service clusterip myapp --tcp=80:80
kubectl create namespace dev
kubectl create configmap myconfig --from-literal=key=value
kubectl create secret generic mysecret --from-literal=password=secret123

Create resources from file or command line.

Apply Configuration

kubectl apply -f <file>
kubectl apply -f deployment.yaml
kubectl apply -f . (apply all files in directory)
kubectl apply -k <directory> (kustomize)

Apply configuration to resources (declarative management).

Delete Resources

kubectl delete <resource> <name>
kubectl delete -f <file>
kubectl delete pod myapp-pod
kubectl delete deployment myapp
kubectl delete pods -l app=myapp
kubectl delete all --all

Delete resources by name, file, or label selector.

Edit Resources

kubectl edit <resource> <name>
kubectl edit deployment myapp

Edit resource in default editor.

Patch Resources

kubectl patch <resource> <name> -p '<patch>'
kubectl patch deployment myapp -p '{"spec":{"replicas":3}}'

Update resource fields using strategic merge patch.

Pods

Run Pod

kubectl run <name> --image=<image>
kubectl run nginx --image=nginx --port=80
kubectl run debug --image=busybox -it --rm -- sh

Run a pod. Use --rm for temporary pods, -it for interactive terminal.

Get Pod Logs

kubectl logs <pod-name>
kubectl logs -f <pod-name>
kubectl logs <pod-name> -c <container-name>
kubectl logs --previous <pod-name>
kubectl logs --tail=100 <pod-name>
kubectl logs -l app=myapp

View pod logs. Use -f to follow, -c for specific container, --previous for previous instance.

Execute Command in Pod

kubectl exec <pod-name> -- <command>
kubectl exec -it <pod-name> -- bash
kubectl exec <pod-name> -c <container> -- ls /app

Execute command in container. Use -it for interactive shell.

Port Forward

kubectl port-forward <pod-name> <local-port>:<pod-port>
kubectl port-forward pod/myapp 8080:80
kubectl port-forward service/myapp 8080:80

Forward local port to pod or service port.

Copy Files

kubectl cp <pod-name>:/path/to/file ./local/path
kubectl cp ./local/file <pod-name>:/path/to/destination
kubectl cp <namespace>/<pod>:/path/file ./local

Copy files to/from pod containers.

Deployments

Create Deployment

kubectl create deployment <name> --image=<image>
kubectl create deployment nginx --image=nginx:1.21
kubectl create deployment web --image=myapp --replicas=3

Create deployment with specified image.

Scale Deployment

kubectl scale deployment <name> --replicas=<count>
kubectl scale deployment myapp --replicas=5
kubectl autoscale deployment myapp --min=2 --max=10 --cpu-percent=80

Scale deployment replicas manually or with autoscaling.

Update Deployment

kubectl set image deployment/<name> <container>=<image>
kubectl set image deployment/myapp myapp=myapp:v2
kubectl rollout restart deployment/myapp

Update deployment image or restart.

Rollout Management

kubectl rollout status deployment/<name>
kubectl rollout history deployment/<name>
kubectl rollout undo deployment/<name>
kubectl rollout undo deployment/<name> --to-revision=2

Manage deployment rollouts and rollbacks.

Services

Expose Service

kubectl expose deployment <name> --port=<port> --target-port=<target-port>
kubectl expose deployment myapp --port=80 --target-port=8080 --type=LoadBalancer
kubectl expose pod myapp --port=80 --name=myapp-service

Create service to expose pods.

Get Endpoints

kubectl get endpoints
kubectl get endpoints <service-name>

List service endpoints.

ConfigMaps and Secrets

Create ConfigMap

kubectl create configmap <name> --from-literal=<key>=<value>
kubectl create configmap myconfig --from-file=config.txt
kubectl create configmap myconfig --from-env-file=.env

Create ConfigMap from literals, files, or env files.

Create Secret

kubectl create secret generic <name> --from-literal=<key>=<value>
kubectl create secret generic mysecret --from-file=secret.txt
kubectl create secret docker-registry regcred --docker-server=<server> --docker-username=<user> --docker-password=<pass>
kubectl create secret tls tls-secret --cert=cert.crt --key=cert.key

Create secrets for sensitive data.

Get ConfigMap/Secret Data

kubectl get configmap <name> -o yaml
kubectl get secret <name> -o jsonpath='{.data.password}' | base64 -d

View ConfigMap or Secret contents.

Namespaces

List Namespaces

kubectl get namespaces
kubectl get ns

List all namespaces.

Create Namespace

kubectl create namespace <name>
kubectl create ns dev

Create a new namespace.

Delete Namespace

kubectl delete namespace <name>

Delete namespace and all its resources.

Set Default Namespace

kubectl config set-context --current --namespace=<namespace>

Set default namespace for current context.

Resource Quotas and Limits

Resource Usage

kubectl top nodes
kubectl top pods
kubectl top pods -n <namespace>
kubectl top pods --containers

Show resource usage (requires metrics-server).

Jobs and CronJobs

Create Job

kubectl create job <name> --image=<image>
kubectl create job test --image=busybox -- echo "Hello"

Create a one-time job.

Create CronJob

kubectl create cronjob <name> --image=<image> --schedule="<cron>"
kubectl create cronjob backup --image=backup:latest --schedule="0 2 * * *"

Create scheduled job.

Debugging

Get Events

kubectl get events
kubectl get events --sort-by='.lastTimestamp'
kubectl get events -n <namespace>

View cluster events.

Debug Pod

kubectl debug <pod-name> -it --image=busybox
kubectl debug node/<node-name> -it --image=busybox

Create debugging container for troubleshooting.

Proxy

kubectl proxy
kubectl proxy --port=8080

Create proxy to Kubernetes API server.

Examples

Deploy Application

# Create deployment
kubectl create deployment myapp --image=myapp:v1 --replicas=3

# Expose as service
kubectl expose deployment myapp --port=80 --type=LoadBalancer

# Check status
kubectl get pods -l app=myapp
kubectl get service myapp

# View logs
kubectl logs -l app=myapp -f

Update Application

# Update image
kubectl set image deployment/myapp myapp=myapp:v2

# Watch rollout
kubectl rollout status deployment/myapp

# Check history
kubectl rollout history deployment/myapp

# Rollback if needed
kubectl rollout undo deployment/myapp

Debug Application

# Check pod status
kubectl get pods
kubectl describe pod myapp-abc123

# View logs
kubectl logs myapp-abc123
kubectl logs myapp-abc123 --previous

# Execute commands
kubectl exec -it myapp-abc123 -- sh
kubectl exec myapp-abc123 -- env

# Port forward for testing
kubectl port-forward myapp-abc123 8080:80

ConfigMap and Secret Usage

# Create ConfigMap
kubectl create configmap app-config \
  --from-literal=db_host=localhost \
  --from-literal=db_port=5432

# Create Secret
kubectl create secret generic app-secret \
  --from-literal=db_password=secret123

# Use in deployment (apply from file)
kubectl apply -f deployment-with-config.yaml

Manage Multiple Environments

# Create namespaces
kubectl create namespace dev
kubectl create namespace staging
kubectl create namespace prod

# Deploy to specific namespace
kubectl apply -f deployment.yaml -n dev

# Switch default namespace
kubectl config set-context --current --namespace=dev

# View resources across all namespaces
kubectl get pods --all-namespaces

Notes

Contexts: Use contexts to switch between clusters and namespaces
Declarative Management: Prefer kubectl apply over kubectl create for reproducibility
Labels: Use labels for resource organization and selection
Namespaces: Isolate resources using namespaces
YAML: Most resources are defined in YAML manifests
Selectors: Use -l key=value to filter resources by labels
JSON Path: Use -o jsonpath for precise field extraction
Dry Run: Test changes with --dry-run=client -o yaml
Force Delete: Use --force --grace-period=0 for stuck pods (use carefully)
API Resources: Run kubectl api-resources to list all resource types
Explain: Use kubectl explain <resource> for resource documentation
Completion: Enable shell completion with kubectl completion bash|zsh
Plugins: Extend kubectl with plugins using Krew plugin manager
Config: kubeconfig file location: ~/.kube/config

kubectl