# Referensi Cepat Kubernetes

*kubectl, pod, deployment, service, config, debugging*

> Source: Kubernetes Documentation (kubernetes.io/docs) · MIT

## Dasar kubectl

### Info Cluster

```
kubectl cluster-info
kubectl get nodes
kubectl config current-context
kubectl config use-context my-cluster
```

### Perintah Utama

| Command | Description |
|---------|-------------|
| `kubectl get <resource>` | Tampilkan daftar resource |
| `kubectl describe <resource> <name>` | Info detail resource |
| `kubectl create -f file.yaml` | Buat resource dari file |
| `kubectl apply -f file.yaml` | Buat atau perbarui resource |
| `kubectl delete -f file.yaml` | Hapus resource dari file |
| `kubectl edit <resource> <name>` | Edit resource di tempat |
| `kubectl api-resources` | Tampilkan semua tipe resource |

### Format Output

| Command | Description |
|---------|-------------|
| `-o wide` | Kolom tambahan (IP, node) |
| `-o yaml` | Output YAML lengkap |
| `-o json` | Output JSON lengkap |
| `-o jsonpath='{.spec}'` | Ekstrak field tertentu |
| `--sort-by=.metadata.name` | Urutkan output berdasarkan field |

## Pod

### Operasi Pod

```
kubectl get pods
kubectl get pods -A                  # all namespaces
kubectl run nginx --image=nginx      # quick pod
kubectl delete pod nginx
```

### YAML Pod

```
apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels: { app: myapp }
spec:
  containers:
    - name: app
      image: nginx:1.27
      ports:
        - containerPort: 80
```

### Nilai Status Pod

| Command | Description |
|---------|-------------|
| `Running` | Semua container sudah berjalan |
| `Pending` | Menunggu penjadwalan atau pull image |
| `CrashLoopBackOff` | Container terus crash dan restart |
| `ImagePullBackOff` | Gagal mengunduh image container |
| `Completed` | Selesai berjalan (Jobs) |

## Deployment

### YAML Deployment

```
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
spec:
  replicas: 3
  selector:
    matchLabels: { app: web }
  template:
    metadata:
      labels: { app: web }
    spec:
      containers:
        - name: web
          image: nginx:1.27
          ports:
            - containerPort: 80
```

### Perintah Deployment

| Command | Description |
|---------|-------------|
| `kubectl get deploy` | Tampilkan deployment |
| `kubectl scale deploy web --replicas=5` | Skala replica |
| `kubectl set image deploy/web web=nginx:1.28` | Update image (rolling) |
| `kubectl rollout status deploy/web` | Pantau progres rollout |
| `kubectl rollout undo deploy/web` | Rollback ke revisi sebelumnya |
| `kubectl rollout history deploy/web` | Lihat riwayat revisi |

## Service

### Jenis Service

| Command | Description |
|---------|-------------|
| `ClusterIP` | Internal saja (default) |
| `NodePort` | Ekspos di IP setiap node pada port statis |
| `LoadBalancer` | Load balancer eksternal (cloud) |
| `ExternalName` | Alias DNS ke layanan eksternal |

### YAML Service

```
apiVersion: v1
kind: Service
metadata:
  name: web-svc
spec:
  type: ClusterIP
  selector: { app: web }
  ports:
    - port: 80
      targetPort: 80
```

### Ekspos Cepat

```
kubectl expose deploy web --port=80 --type=ClusterIP
kubectl expose deploy web --port=80 --type=NodePort
kubectl get svc
```

## ConfigMap & Secret

### ConfigMap

```
kubectl create configmap app-cfg \
  --from-literal=DB_HOST=db.example.com \
  --from-file=config.ini
```

### Secret

```
kubectl create secret generic db-creds \
  --from-literal=username=admin \
  --from-literal=password=s3cret
```

### Penggunaan dalam Pod

```
# As environment variables
envFrom:
  - configMapRef: { name: app-cfg }
  - secretRef:    { name: db-creds }

# As volume mount
volumes:
  - name: cfg
    configMap: { name: app-cfg }
```

### Perintah

| Command | Description |
|---------|-------------|
| `kubectl get cm` | Tampilkan ConfigMap |
| `kubectl get secret` | Tampilkan Secret |
| `kubectl describe cm app-cfg` | Tampilkan data ConfigMap |
| `kubectl get secret db-creds -o yaml` | Tampilkan Secret (base64-encoded) |

## Namespace

### Perintah Namespace

| Command | Description |
|---------|-------------|
| `kubectl get ns` | Tampilkan namespace |
| `kubectl create ns staging` | Buat namespace |
| `kubectl delete ns staging` | Hapus namespace dan semua resource |
| `kubectl get pods -n staging` | Tampilkan pod di namespace |
| `kubectl get pods -A` | Tampilkan pod di semua namespace |

### Atur Namespace Default

```
kubectl config set-context --current \
  --namespace=staging
```

## Volume

### PersistentVolumeClaim

```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data-pvc
spec:
  accessModes: [ReadWriteOnce]
  resources:
    requests: { storage: 10Gi }
```

### Mount dalam Pod

```
volumes:
  - name: data
    persistentVolumeClaim:
      claimName: data-pvc
containers:
  - volumeMounts:
      - name: data
        mountPath: /app/data
```

### Jenis Volume

| Command | Description |
|---------|-------------|
| `emptyDir` | Direktori sementara, dihapus bersama pod |
| `hostPath` | Mount path filesystem host |
| `persistentVolumeClaim` | Penyimpanan persisten (PVC) |
| `configMap` | Mount ConfigMap sebagai file |
| `secret` | Mount Secret sebagai file |

## Ingress

### YAML Ingress

```
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: web-ingress
spec:
  rules:
    - host: app.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: web-svc
                port: { number: 80 }
```

### Catatan Ingress

| Command | Description |
|---------|-------------|
| `Ingress Controller` | Wajib ada (nginx-ingress, traefik, dll.) |
| `pathType: Prefix` | Cocokkan awalan URL |
| `pathType: Exact` | Cocokkan path URL tepat |
| `TLS` | Tambahkan bagian `tls:` dengan nama secret |

## Debugging

### Perintah Diagnostik

| Command | Description |
|---------|-------------|
| `kubectl logs <pod>` | stdout/stderr container |
| `kubectl logs <pod> -c <ctr>` | Log container tertentu |
| `kubectl logs <pod> --previous` | Log dari container yang crash |
| `kubectl describe pod <pod>` | Event, kondisi, status |
| `kubectl exec -it <pod> -- sh` | Masuk shell ke container |
| `kubectl port-forward <pod> 8080:80` | Forward port lokal ke pod |
| `kubectl top pods` | Penggunaan CPU/memori (metrics-server) |
| `kubectl get events --sort-by=.lastTimestamp` | Timeline event cluster |

### Pod Debug

```
kubectl run debug --rm -it --image=busybox -- sh
# or attach ephemeral container
kubectl debug -it <pod> --image=busybox
```

## Pola Umum

### Label & Selector

```
kubectl get pods -l app=web
kubectl get pods -l 'env in (prod,staging)'
kubectl label pod myapp env=prod
```

### Batas Resource

```
resources:
  requests: { cpu: 100m, memory: 128Mi }
  limits:   { cpu: 500m, memory: 256Mi }
```

### Liveness & Readiness

```
livenessProbe:
  httpGet: { path: /healthz, port: 8080 }
  initialDelaySeconds: 5
  periodSeconds: 10
readinessProbe:
  httpGet: { path: /ready, port: 8080 }
```

### Resep Cepat

| Command | Description |
|---------|-------------|
| `Dry run` | `kubectl apply -f file.yaml --dry-run=client` |
| `Generate YAML` | `kubectl create deploy web --image=nginx --dry-run=client -o yaml` |
| `Watch` | `kubectl get pods -w` |
| `Copy file` | `kubectl cp file.txt pod:/tmp/` |
| `Restart deploy` | `kubectl rollout restart deploy/web` |