kubectl Basics

# ===== Contexts + namespaces =====
kubectl config get-contexts
kubectl config use-context my-cluster
kubectl config current-context
kubectl config set-context --current --namespace=dev

# Or use kubectx + kubens for fast switching.

# ===== Get / describe =====
kubectl get pods
kubectl get pods -A                         # all namespaces
kubectl get pods -n kube-system
kubectl get pods -l app=shop                 # label selector
kubectl get pods -o wide                     # IPs, nodes
kubectl get pods -o yaml                     # full YAML
kubectl get pods -o jsonpath='{.items[*].metadata.name}'

kubectl describe pod my-pod
kubectl describe svc shop

# ===== Logs =====
kubectl logs my-pod
kubectl logs my-pod -c api                   # specific container in pod
kubectl logs -f my-pod                       # follow
kubectl logs -l app=shop --tail=200          # by label
kubectl logs my-pod --previous               # previous container's logs

# Stern for multi-pod tail:
stern -n default '.*'

# ===== Exec =====
kubectl exec -it my-pod -- sh
kubectl exec my-pod -- env
kubectl exec my-pod -- cat /etc/hostname

# ===== Apply / delete =====
kubectl apply -f deploy.yaml
kubectl apply -f ./k8s/ -R                   # entire folder
kubectl delete -f deploy.yaml
kubectl delete pod my-pod                     # restarts under Deployment
kubectl delete pods --all                     # all in current namespace

# Server-side apply (idempotent + diffable):
kubectl apply --server-side -f deploy.yaml

# ===== Rollout =====
kubectl rollout status deploy/shop
kubectl rollout history deploy/shop
kubectl rollout undo deploy/shop
kubectl rollout restart deploy/shop          # rolling restart with no spec change

# ===== 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
kubectl port-forward pod/my-pod 5432:5432

# ===== Run + create =====
kubectl run mycurl --rm -it --image=curlimages/curl -- sh
kubectl create job hello --image=busybox -- echo hi

# ===== Diff + dry run =====
kubectl diff -f deploy.yaml                  # show changes before apply
kubectl apply --dry-run=client -f deploy.yaml
kubectl apply --dry-run=server -f deploy.yaml

# ===== Imperative -> declarative export =====
kubectl create deploy nginx --image=nginx -o yaml --dry-run=client > deploy.yaml
# Edit + version + apply.

# ===== Events =====
kubectl get events --sort-by=.metadata.creationTimestamp -A | tail -20

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

# ===== Patterns to internalise =====
# - Set the namespace via context, not -n on every command
# - Use labels + selectors for batch ops (logs / delete / scale)
# - kubectl diff before apply on prod
# - Rollout restart for config / secret changes that need fresh pods

# ===== Pitfalls =====
# - Editing live resources with 'kubectl edit' -> drifts from git
# - Deleting StatefulSet pods to 'restart' (data risk)
# - Running 'kubectl apply' on prod from a wrong context
# - 'kubectl exec' for ops without a record (use audit logs)

kubectl get pods
kubectl get all -A
kubectl apply -f deployment.yaml
kubectl logs -f pod/api-1