freeleaps-ops/docs/examples/kubectl-quick-reference.md

kubectl Quick Reference Guide

🚀 Essential Commands for Junior Engineers

Basic Resource Management

# Get resources
kubectl get pods
kubectl get deployments
kubectl get services
kubectl get namespaces
kubectl get configmaps
kubectl get secrets
kubectl get pvc
kubectl get ingress

# Get all resources in namespace
kubectl get all -n <namespace>

# Get resources with labels
kubectl get pods -l app=web-app
kubectl get pods -l environment=production

# Get resources in wide format
kubectl get pods -o wide
kubectl get nodes -o wide

Resource Creation

# Create from YAML file
kubectl apply -f <file.yaml>

# Create from directory
kubectl apply -f <directory>/

# Create from URL
kubectl apply -f https://raw.githubusercontent.com/...

# Create resources directly
kubectl create namespace my-app
kubectl create deployment nginx --image=nginx:latest
kubectl create service clusterip nginx --tcp=80:80
kubectl create configmap app-config --from-literal=DB_HOST=postgres
kubectl create secret generic db-secret --from-literal=DB_PASSWORD=secret123

Resource Inspection

# Describe resources
kubectl describe pod <pod-name>
kubectl describe deployment <deployment-name>
kubectl describe service <service-name>
kubectl describe namespace <namespace-name>

# Get resource YAML
kubectl get pod <pod-name> -o yaml
kubectl get deployment <deployment-name> -o yaml

# Get resource in specific format
kubectl get pod <pod-name> -o json
kubectl get pod <pod-name> -o jsonpath='{.spec.containers[0].image}'

Logs and Debugging

# View logs
kubectl logs <pod-name>
kubectl logs <pod-name> -f  # Follow logs
kubectl logs <pod-name> --previous  # Previous container
kubectl logs <pod-name> --tail=100  # Last 100 lines

# Execute commands in pods
kubectl exec -it <pod-name> -- /bin/bash
kubectl exec <pod-name> -- ls /app
kubectl exec <pod-name> -- cat /etc/passwd

# Port forwarding
kubectl port-forward <pod-name> 8080:80
kubectl port-forward service/<service-name> 8080:80
kubectl port-forward deployment/<deployment-name> 8080:80

Scaling and Updates

# Scale deployments
kubectl scale deployment <deployment-name> --replicas=5
kubectl scale deployment <deployment-name> --replicas=0  # Scale to zero

# Update deployments
kubectl set image deployment/<deployment-name> <container-name>=<new-image>
kubectl set image deployment/nginx nginx=nginx:1.21

# Rollout management
kubectl rollout status deployment/<deployment-name>
kubectl rollout history deployment/<deployment-name>
kubectl rollout undo deployment/<deployment-name>
kubectl rollout pause deployment/<deployment-name>
kubectl rollout resume deployment/<deployment-name>

Resource Deletion

# Delete resources
kubectl delete pod <pod-name>
kubectl delete deployment <deployment-name>
kubectl delete service <service-name>
kubectl delete namespace <namespace-name>

# Delete from YAML file
kubectl delete -f <file.yaml>

# Delete all resources in namespace
kubectl delete all --all -n <namespace>

# Force delete (use with caution)
kubectl delete pod <pod-name> --force --grace-period=0

Context and Namespace Management

# View current context
kubectl config current-context

# List contexts
kubectl config get-contexts

# Switch context
kubectl config use-context <context-name>

# Set default namespace
kubectl config set-context --current --namespace=<namespace>

# View cluster info
kubectl cluster-info
kubectl cluster-info dump

Resource Monitoring

# Check resource usage
kubectl top pods
kubectl top nodes
kubectl top pods --containers

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

# Check resource quotas
kubectl get resourcequota
kubectl describe resourcequota <quota-name>

Troubleshooting Commands

# Check node status
kubectl get nodes
kubectl describe node <node-name>

# Check service endpoints
kubectl get endpoints <service-name>
kubectl describe endpoints <service-name>

# Check persistent volumes
kubectl get pv
kubectl get pvc
kubectl describe pv <pv-name>

# Check ingress
kubectl get ingress
kubectl describe ingress <ingress-name>

# Check jobs and cronjobs
kubectl get jobs
kubectl get cronjobs
kubectl describe job <job-name>
kubectl describe cronjob <cronjob-name>

Useful Aliases

# Add to your .bashrc or .zshrc
alias k='kubectl'
alias kg='kubectl get'
alias kd='kubectl describe'
alias kl='kubectl logs'
alias ke='kubectl exec -it'
alias kp='kubectl port-forward'
alias ka='kubectl apply -f'
alias kdel='kubectl delete'
alias kctx='kubectl config use-context'
alias kns='kubectl config set-context --current --namespace'

Common Patterns

# Get all pods with their IPs
kubectl get pods -o wide

# Get all services with their endpoints
kubectl get services -o wide

# Get all resources in a namespace
kubectl get all -n <namespace>

# Get resources by label
kubectl get pods -l app=web-app,environment=production

# Get resources sorted by creation time
kubectl get pods --sort-by=.metadata.creationTimestamp

# Get resources in custom columns
kubectl get pods -o custom-columns=NAME:.metadata.name,STATUS:.status.phase,AGE:.metadata.creationTimestamp

Advanced Commands

# Patch resources
kubectl patch deployment <deployment-name> -p '{"spec":{"replicas":5}}'

# Edit resources
kubectl edit deployment <deployment-name>
kubectl edit configmap <configmap-name>

# Copy files
kubectl cp <local-file> <pod-name>:/path/in/pod
kubectl cp <pod-name>:/path/in/pod <local-file>

# Run temporary pods
kubectl run test-pod --image=busybox --rm -it --restart=Never -- wget -O- <service-name>:<port>

# Check API resources
kubectl api-resources
kubectl explain <resource-type>

Context-Specific Commands

# For debugging network issues
kubectl run test-pod --image=busybox --rm -it --restart=Never -- wget -O- <service-name>:<port>

# For checking storage
kubectl run test-pod --image=busybox --rm -it --restart=Never -- ls /data

# For testing DNS
kubectl run test-pod --image=busybox --rm -it --restart=Never -- nslookup <service-name>

# For checking secrets
kubectl run test-pod --rm -it --restart=Never --image=busybox -- env | grep DB_

⚠️ Bad Practices to Avoid

❌ DON'T DO THIS

# ❌ NEVER use kubectl run for production applications
kubectl run my-app --image=my-app:latest --port=8080

# ❌ NEVER create standalone Pods for services
kubectl run database --image=postgres:13 --port=5432

# ❌ NEVER use imperative commands for production
kubectl run nginx --image=nginx:latest

# ❌ NEVER delete Pods directly (they'll be recreated by Deployment)
kubectl delete pod <pod-name>

# ❌ NEVER use --force without understanding the consequences
kubectl delete pod <pod-name> --force --grace-period=0

✅ DO THIS INSTEAD

# ✅ Use Deployments for applications
kubectl create deployment my-app --image=my-app:latest

# ✅ Use Helm charts for complex applications
helm install my-app ./my-app-chart --namespace my-app

# ✅ Use kubectl apply for declarative deployments
kubectl apply -f deployment.yaml

# ✅ Use StatefulSets for databases
kubectl apply -f statefulset.yaml

# ✅ Delete Deployments, not Pods
kubectl delete deployment <deployment-name>

# ✅ Use proper resource management
kubectl scale deployment <deployment-name> --replicas=0

🔧 When kubectl run is Acceptable

# ✅ OK: One-time debugging pods
kubectl run debug-pod --image=busybox --rm -it --restart=Never -- nslookup my-service

# ✅ OK: Temporary testing
kubectl run test-pod --image=nginx --rm -it --restart=Never -- curl http://my-service:80

# ✅ OK: Quick experiments (development only)
kubectl run temp-pod --image=nginx --port=80

# ✅ OK: Troubleshooting network issues
kubectl run test-pod --image=busybox --rm -it --restart=Never -- wget -O- my-service:80

🏭 Your Codebase Best Practices

Your Actual Commands

# 🏭 REAL COMMANDS FROM YOUR CODEBASE
# From freeleaps-devops-reconciler/scripts/deploy.sh

# Helm deployment (primary method)
helm install/upgrade "$RELEASE_NAME" . \
  --namespace "$NAMESPACE" \
  --create-namespace \
  -f "$VALUES_FILE" \
  --set "image.tag=$IMAGE_TAG"

# kubectl apply (secondary method)
kubectl apply -f <directory>/

# Status checking
kubectl get pods -n "$NAMESPACE" -l "app.kubernetes.io/name=freeleaps-devops-reconciler"
kubectl logs -n "$NAMESPACE" deployment/"$RELEASE_NAME"

Best Practices

1. Always use namespaces to organize resources
2. Use labels for better resource management
3. Set resource limits on all containers
4. Use health checks for reliability
5. Use ConfigMaps and Secrets for configuration
6. Test changes in a staging environment first
7. Keep kubectl updated to match your cluster version
8. Use Deployments, not standalone Pods
9. Use Helm charts for complex applications
10. Use declarative YAML files

Common Mistakes to Avoid

# ❌ Don't do this
kubectl run nginx --image=nginx  # Creates a pod, not a deployment

# ✅ Do this instead
kubectl create deployment nginx --image=nginx

# ❌ Don't do this
kubectl delete pod <pod-name>  # Pod will be recreated by deployment

# ✅ Do this instead
kubectl delete deployment <deployment-name>

# ❌ Don't do this
kubectl exec <pod-name> -- rm -rf /  # Dangerous command

# ✅ Do this instead
kubectl exec <pod-name> -- ls /  # Safe inspection command