kubectl Mastery

# View current context
kubectl config current-context

# List all contexts
kubectl config get-contexts

# Switch context
kubectl config use-context production-cluster

# Set default namespace for current context
kubectl config set-context --current --namespace=production

# View full kubeconfig
kubectl config view

# Merge kubeconfig files
KUBECONFIG=~/.kube/config:~/new-cluster.yaml kubectl config view --merge --flatten > ~/.kube/merged-config
mv ~/.kube/merged-config ~/.kube/config

# List resources
kubectl get pods
kubectl get pods -n production
kubectl get pods -A                          # All namespaces
kubectl get pods -l app=api-server           # By label
kubectl get pods --field-selector status.phase=Running

# Wide output with extra info
kubectl get pods -o wide

# YAML output
kubectl get pod my-pod -o yaml

# JSON output
kubectl get pod my-pod -o json

# Custom columns
kubectl get pods -o custom-columns='NAME:.metadata.name,STATUS:.status.phase,IP:.status.podIP,NODE:.spec.nodeName'

# JSONPath for specific fields
kubectl get pods -o jsonpath='{.items[*].metadata.name}'
kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="InternalIP")].address}'

# Sort by field
kubectl get pods --sort-by=.metadata.creationTimestamp
kubectl get pods --sort-by=.status.startTime

# Watch for changes in real time
kubectl get pods -w

# Detailed info about a resource
kubectl describe pod my-pod
kubectl describe deployment api-server
kubectl describe node worker-node-1

# View events (recent activity)
kubectl get events --sort-by=.lastTimestamp
kubectl get events -n production --field-selector reason=Failed

# Explain a resource type and its fields
kubectl explain pod.spec.containers.resources
kubectl explain deployment.spec.strategy

# Apply manifests (declarative)
kubectl apply -f deployment.yaml
kubectl apply -f ./manifests/          # Apply all files in a directory
kubectl apply -f https://raw.githubusercontent.com/...  # Apply from URL

# Create resources (imperative)
kubectl create deployment nginx --image=nginx:1.25 --replicas=3
kubectl create service clusterip my-svc --tcp=80:8080
kubectl create configmap app-config --from-literal=key=value
kubectl create secret generic db-pass --from-literal=password=secret

# Edit a resource in your editor
kubectl edit deployment api-server -n production

# Patch a resource
kubectl patch deployment api-server -n production -p '{"spec":{"replicas":5}}'

# Label resources
kubectl label pods my-pod environment=production
kubectl label pods -l app=api tier=backend

# Annotate resources
kubectl annotate deployment api-server description="Main API server"

# View container logs
kubectl logs my-pod
kubectl logs my-pod -c sidecar-container   # Specific container
kubectl logs my-pod --previous              # Previous container (after crash)
kubectl logs -l app=api-server --all-containers  # All pods matching label
kubectl logs my-pod -f                      # Follow/stream logs
kubectl logs my-pod --tail=100              # Last 100 lines
kubectl logs my-pod --since=1h              # Last hour

# Execute commands in a container
kubectl exec my-pod -- ls /app
kubectl exec -it my-pod -- /bin/sh          # Interactive shell
kubectl exec -it my-pod -c web -- bash      # Specific container

# Port forwarding
kubectl port-forward pod/my-pod 8080:3000
kubectl port-forward svc/api-service 8080:80
kubectl port-forward deployment/api-server 8080:3000

# Copy files to/from a container
kubectl cp my-pod:/var/log/app.log ./app.log
kubectl cp ./config.yaml my-pod:/app/config.yaml

# Run a debug pod
kubectl run debug --image=busybox --rm -it -- /bin/sh
kubectl run debug --image=nicolaka/netshoot --rm -it -- /bin/bash

# Debug a node
kubectl debug node/worker-node-1 -it --image=busybox

# Top (resource usage)
kubectl top pods -n production
kubectl top nodes

# Shell aliases (add to ~/.bashrc or ~/.zshrc)
alias k='kubectl'
alias kgp='kubectl get pods'
alias kgs='kubectl get services'
alias kgd='kubectl get deployments'
alias kga='kubectl get all'
alias kdp='kubectl describe pod'
alias kaf='kubectl apply -f'
alias kdf='kubectl delete -f'
alias kl='kubectl logs'
alias klf='kubectl logs -f'
alias ke='kubectl exec -it'
alias kns='kubectl config set-context --current --namespace'

# Enable kubectl autocompletion
source <(kubectl completion bash)  # bash
source <(kubectl completion zsh)   # zsh

# Dry run to generate YAML
kubectl create deployment nginx --image=nginx --dry-run=client -o yaml > deployment.yaml
kubectl create service clusterip my-svc --tcp=80:8080 --dry-run=client -o yaml > service.yaml

# Diff before applying
kubectl diff -f deployment.yaml