Kubernetes 기초: 컨테이너 오케스트레이션 시작하기

Control Plane
├── API Server      # 모든 통신의 중심
├── etcd           # 클러스터 상태 저장소
├── Controller     # 상태 관리
├── Scheduler      # Pod 배치 결정
└── Cloud Controller Manager

Worker Node
├── kubelet        # 노드의 에이전트
├── kube-proxy     # 네트워크 프록시
└── Container Runtime (Docker/containerd)

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:1.21
    ports:
    - containerPort: 80

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.21
        ports:
        - containerPort: 80

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
  - port: 80
    targetPort: 80
  type: ClusterIP

# macOS
brew install minikube

# Linux
curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64
sudo install minikube-linux-amd64 /usr/local/bin/minikube

# 클러스터 시작
minikube start

# macOS
brew install kubectl

# Linux
curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl

# 버전 확인
kubectl version --client

# deployment.yaml 파일 생성
cat <<EOF > deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-k8s
spec:
  replicas: 3
  selector:
    matchLabels:
      app: hello-k8s
  template:
    metadata:
      labels:
        app: hello-k8s
    spec:
      containers:
      - name: hello-k8s
        image: nginx:alpine
        ports:
        - containerPort: 80
        env:
        - name: MESSAGE
          value: "Hello Kubernetes!"
EOF

# 배포
kubectl apply -f deployment.yaml

# service.yaml 파일 생성
cat <<EOF > service.yaml
apiVersion: v1
kind: Service
metadata:
  name: hello-k8s-service
spec:
  selector:
    app: hello-k8s
  ports:
  - port: 80
    targetPort: 80
  type: NodePort
EOF

# 서비스 생성
kubectl apply -f service.yaml

# Pod 상태 확인
kubectl get pods

# Service 확인
kubectl get services

# Minikube에서 서비스 접속
minikube service hello-k8s-service

# 리소스 조회
kubectl get pods                    # Pod 목록
kubectl get deployments             # Deployment 목록
kubectl get services               # Service 목록
kubectl get nodes                  # Node 목록

# 상세 정보
kubectl describe pod <pod-name>
kubectl describe deployment <deployment-name>

# 로그 확인
kubectl logs <pod-name>
kubectl logs -f <pod-name>         # 실시간 로그

# Pod 접속
kubectl exec -it <pod-name> -- /bin/bash

# 스케일링
kubectl scale deployment <deployment-name> --replicas=5

# 롤링 업데이트
kubectl set image deployment/<deployment-name> <container-name>=<new-image>

# 삭제
kubectl delete pod <pod-name>
kubectl delete deployment <deployment-name>
kubectl delete service <service-name>

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  database_url: "mysql://localhost:3306/mydb"
  api_key: "development-key"

apiVersion: v1
kind: Secret
metadata:
  name: app-secret
type: Opaque
data:
  username: YWRtaW4=  # base64 encoded
  password: MWYyZDFlMmU2N2Rm  # base64 encoded

apiVersion: v1
kind: Pod
metadata:
  name: app-pod
spec:
  containers:
  - name: app
    image: myapp:latest
    env:
    - name: DB_URL
      valueFrom:
        configMapKeyRef:
          name: app-config
          key: database_url
    - name: DB_PASSWORD
      valueFrom:
        secretKeyRef:
          name: app-secret
          key: password

# 네임스페이스 생성
kubectl create namespace development
kubectl create namespace production

# 네임스페이스 지정하여 리소스 생성
kubectl apply -f deployment.yaml -n development

# 네임스페이스의 모든 리소스 조회
kubectl get all -n development

# 기본 네임스페이스 변경
kubectl config set-context --current --namespace=development

# Node 리소스 사용량
kubectl top nodes

# Pod 리소스 사용량
kubectl top pods

# 특정 Pod의 상세 메트릭
kubectl top pod <pod-name> --containers

# Pod가 시작되지 않을 때
kubectl describe pod <pod-name>
kubectl logs <pod-name> --previous

# 이벤트 확인
kubectl get events --sort-by=.metadata.creationTimestamp

# Pod 재시작
kubectl rollout restart deployment <deployment-name>

# 레이블로 필터링
kubectl get pods -l app=nginx
kubectl get pods -l 'environment in (production, staging)'

kubectl apply -f deployment.yaml --dry-run=client

# 기존 리소스에서 YAML 추출
kubectl get deployment nginx-deployment -o yaml > deployment-backup.yaml

# imperative 명령으로 YAML 생성
kubectl create deployment nginx --image=nginx --dry-run=client -o yaml > deployment.yaml