Kubernetes 입문

# Kubernetes 입문 가이드

## 학습 목표
Kubernetes로 컨테이너 오케스트레이션을 구현합니다.

## 1. Kubernetes란?
컨테이너 오케스트레이션 플랫폼입니다.
- 자동 배포 및 스케일링
- 셀프 힐링
- 로드 밸런싱
- 롤링 업데이트

## 2. 핵심 개념
Pod: 최소 배포 단위 (컨테이너 그룹)
Deployment: Pod 관리 및 복제
Service: 네트워크 노출
ConfigMap: 설정 데이터
Secret: 민감한 데이터
Namespace: 리소스 분리

## 3. 로컬 설치
minikube:
minikube start
minikube status
minikube dashboard
minikube stop

kind:
kind create cluster
kind delete cluster

kubectl 설치:
curl -LO https://dl.k8s.io/release/stable.txt

## 4. kubectl 기본 명령어
조회:
kubectl get pods
kubectl get pods -o wide
kubectl get deployments
kubectl get services
kubectl get all

상세 정보:
kubectl describe pod pod-name
kubectl logs pod-name
kubectl logs -f pod-name

실행:
kubectl exec -it pod-name -- sh

삭제:
kubectl delete pod pod-name
kubectl delete -f manifest.yaml

## 5. Pod 생성
pod.yaml:
apiVersion: v1
kind: Pod
metadata:
name: nginx-pod
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:latest
ports:
- containerPort: 80

적용:
kubectl apply -f pod.yaml
kubectl get pods
kubectl delete pod nginx-pod

## 6. Deployment
deployment.yaml:
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
resources:
limits:
memory: "128Mi"
cpu: "500m"

스케일링:
kubectl scale deployment nginx-deployment --replicas=5

업데이트:
kubectl set image deployment/nginx-deployment nginx=nginx:1.22
kubectl rollout status deployment/nginx-deployment
kubectl rollout history deployment/nginx-deployment
kubectl rollout undo deployment/nginx-deployment

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

서비스 타입:
ClusterIP: 클러스터 내부 접근
NodePort: 노드 포트로 외부 노출
LoadBalancer: 클라우드 로드밸런서

NodePort 예시:
spec:
type: NodePort
ports:
- port: 80
targetPort: 80
nodePort: 30080

## 8. ConfigMap
생성:
kubectl create configmap app-config --from-literal=DB_HOST=localhost
kubectl create configmap app-config --from-file=config.txt

yaml:
apiVersion: v1
kind: ConfigMap
metadata:
name: app-config
data:
DB_HOST: localhost
DB_PORT: "3306"

사용:
env:
- name: DB_HOST
valueFrom:
configMapKeyRef:
name: app-config
key: DB_HOST

## 9. Secret
생성:
kubectl create secret generic db-secret --from-literal=password=mysecret

yaml:
apiVersion: v1
kind: Secret
metadata:
name: db-secret
type: Opaque
data:
password: bXlzZWNyZXQ= # base64 인코딩

사용:
env:
- name: DB_PASSWORD
valueFrom:
secretKeyRef:
name: db-secret
key: password

## 10. Ingress
ingress.yaml:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: app-ingress
spec:
rules:
- host: app.example.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: nginx-service
port:
number: 80

## 11. 볼륨
PersistentVolumeClaim:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: data-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi

Pod에서 사용:
volumes:
- name: data
persistentVolumeClaim:
claimName: data-pvc
containers:
- volumeMounts:
- mountPath: /data
name: data

## 12. 모니터링 명령어
리소스 사용량:
kubectl top nodes
kubectl top pods

이벤트:
kubectl get events

로그:
kubectl logs pod-name
kubectl logs -f pod-name --tail=100

디버깅:
kubectl describe pod pod-name
kubectl exec -it pod-name -- sh

## 추천 학습 순서
1. Pod와 기본 명령어
2. Deployment 배포
3. Service 네트워킹
4. ConfigMap/Secret
5. Ingress와 볼륨