Cheatsheet

# ===== Contexts + namespaces =====
kubectl config get-contexts
kubectl config use-context prod
kubectl config set-context --current --namespace=apps

# ===== Get =====
kubectl get pods
kubectl get pods -A                  # all namespaces
kubectl get pods -l app=shop          # by label
kubectl get pods -o wide              # IPs + nodes
kubectl get pods -o yaml              # full YAML
kubectl get all                       # everything in current ns

# ===== Describe + events =====
kubectl describe pod my-pod
kubectl get events --sort-by=.metadata.creationTimestamp -A | tail -20

# ===== Logs =====
kubectl logs my-pod
kubectl logs my-pod -c api            # specific container
kubectl logs -f my-pod                # follow
kubectl logs --previous my-pod        # crashed previous container
kubectl logs -l app=shop --tail=100

# ===== Exec =====
kubectl exec -it my-pod -- sh
kubectl exec my-pod -- env

# ===== Apply / delete =====
kubectl apply -f deploy.yaml
kubectl apply -f ./k8s/                # folder
kubectl delete -f deploy.yaml
kubectl delete pod my-pod
kubectl diff -f deploy.yaml            # preview changes

# ===== Rollout =====
kubectl rollout status deploy/shop
kubectl rollout history deploy/shop
kubectl rollout undo deploy/shop
kubectl rollout restart deploy/shop

# ===== Scale =====
kubectl scale deploy/shop --replicas=5
kubectl autoscale deploy/shop --min=2 --max=10 --cpu-percent=75

# ===== Port forward =====
kubectl port-forward svc/shop 8080:80

# ===== Resource basics =====
# Deployment + Service + Ingress = HTTP app
# StatefulSet = ordered, persistent identity
# DaemonSet = one pod per node (loggers, agents)
# Job + CronJob = one-shot / scheduled
# ConfigMap = non-secret config
# Secret = sensitive config
# PersistentVolumeClaim = storage

# ===== Manifest skeleton =====
apiVersion: apps/v1
kind: Deployment
metadata: { name: app }
spec:
  replicas: 3
  selector: { matchLabels: { app: x } }
  template:
    metadata: { labels: { app: x } }
    spec:
      containers:
        - name: app
          image: ghcr.io/me/app:v1
          ports: [{ containerPort: 3000 }]
          resources:
            requests: { cpu: '100m', memory: '128Mi' }
            limits: { cpu: '500m', memory: '512Mi' }
          readinessProbe: { httpGet: { path: /healthz, port: 3000 } }
          livenessProbe: { httpGet: { path: /healthz, port: 3000 } }

# ===== Troubleshooting common errors =====
# ImagePullBackOff -> wrong image or registry auth
# CrashLoopBackOff -> app crashes; check logs --previous
# Pending -> insufficient resources / PVC unbound / taints
# 503 from Service -> selector mismatch or readiness probe failing
# OOMKilled -> memory limit too low

# ===== Aliases =====
alias k=kubectl
alias kgp='kubectl get pods'
alias kgs='kubectl get svc'
alias kd='kubectl describe'
alias kex='kubectl exec -it'

# ===== Tools =====
kubectx       fast context switching
kubens        fast namespace switching
stern         multi-pod log tailing
k9s           terminal UI dashboard
helm          package manager

kubectl get pods
kubectl describe pod NAME
kubectl logs NAME
kubectl exec -it NAME -- sh
kubectl apply -f file.yaml