Kubernetes Practice

아래 자료들을 참고해 정리하였다. 특히 총 7강의 영상이 큰 도움이 되었다.

GitHub - subicura/workshop-k8s-basic: 쿠버네티스 기본 실습 가이드 kubernetes basicGitHub

쿠버네티스 시작하기 - Kubernetes란 무엇인가?Subicura's Blog

Install

k3s를 설치한다.

curl -sfL https://get.k3s.io | sh -
sudo chown donghyunlee:donghyunlee /etc/rancher/k3s/k3s.yaml

확인

kubectl get nodes

kube config

cp /etc/rancher/k3s/k3s.yaml ~/.kube/config

기본 storage class가 없기때문에 Local path provisioner를 설치한다.

kubectl apply -f https://raw.githubusercontent.com/rancher/local-path-provisioner/master/deploy/local-path-storage.yaml

Set default

kubectl patch storageclass local-path -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

확인

kubectl get storageclass

kubectl

자주 사용하는 kubectl 명령어를 알아본다. 기본 명령어는 아래와 같다.

• apply

  • Apply a configuration to a resource by filename or stdin

• get

  • Display one or many resources

• describe

  • Show details of a specific resource or group of resources

• delete

  • Delete resources by filenames, stdin, resources and names, or by resources and label selector

• logs

  • Print the logs for a container in a pod

• exec

  • Execute a command in a container

get

# pod, replicaset, deployment, service 조회
kubectl get all

# node 조회
kubectl get no
kubectl get node
kubectl get nodes

# 결과 포맷 변경
kubectl get nodes -o wide
kubectl get nodes -o yaml
kubectl get nodes -o json

describe

# kubectl describe type/name
# kubectl describe type name
kubectl describe node/<node name>
kubectl describe node <node name>

그 외 자주 사용하는 명령

kubectl exec -it <POD_NAME>
kubectl logs -f <POD_NAME|TYPE/NAME>

kubectl apply -f <FILENAME>
kubectl delete -f <FILENAME>

Pod

빠른 예제

kubectl run whoami --image subicura/whoami:1 # deprecated soon..
# kubectl get po
# kubectl get pod
kubectl get pods
kubectl get pods -o wide
kubectl get pods -o yaml
kubectl get pods -o json
kubectl logs whoami-<xxxx>
kubectl logs -f whoami-<xxxx>
kubectl exec -it whoami-<xxxx> sh
kubectl describe pods whoami-<xxxx>
kubectl delete pods whoami-<xxxx>
kubectl get pods
kubectl get all
kubectl delete deployment/whoami

YAML 파일을 아래와 같이 만들 수 있다.

# whoami-pod.yml

apiVersion: v1
kind: Pod
metadata:
  name: whoami
  labels:
    type: app
spec:
  containers:
  - name: app
    image: subicura/whoami:1

다음 명령을 통해 적용 및 삭제가 가능하다.

kubectl apply -f <filename>
kubectl delete -f <filename>

Pod ready 개념은 아래 그림을 통해 도식화 할 수 있다.

livenessProbe 예제 (살아 있는지 조사)

# whoami-pod-lp.yml

apiVersion: v1
kind: Pod
metadata:
  name: whoami-lp
  labels:
    type: app
spec:
  containers:
  - name: app
    image: subicura/whoami:1
    livenessProbe:
      httpGet:
        path: /not/exist
        port: 8080
      initialDelaySeconds: 5
      timeoutSeconds: 2 # Default 1
      periodSeconds: 5 # Defaults 10
      failureThreshold: 1 # Defaults 3

readinessProbe 예제 (준비가 되었는지 조사)

# whoami-pod-rp.yml

apiVersion: v1
kind: Pod
metadata:
  name: whoami-rp
  labels:
    type: app
spec:
  containers:
  - name: app
    image: subicura/whoami:1
    readinessProbe:
      httpGet:
        path: /not/exist
        port: 8080
      initialDelaySeconds: 5
      timeoutSeconds: 2 # Default 1
      periodSeconds: 5 # Defaults 10
      failureThreshold: 1 # Defaults 3

health check 예제

# whoami-pod-health.yml

apiVersion: v1
kind: Pod
metadata:
  name: whoami-redis
  labels:
    type: stack
spec:
  containers:
  - name: app
    image: subicura/whoami-redis:1
    env:
    - name: REDIS_HOST
      value: "localhost"
  - name: db
    image: redis

multi container 예제

# whoami-pod-redis.yml

apiVersion: v1
kind: Pod
metadata:
  name: whoami-redis
  labels:
    type: stack
spec:
  containers:
  - name: app
    image: subicura/whoami-redis:1
    env:
    - name: REDIS_HOST
      value: "localhost"
  - name: db
    image: redis

kubectl get all
kubectl logs whoami-redis
kubectl logs whoami-redis app
kubectl logs whoami-redis db
kubectl exec -it whoami-redis
kubectl exec -it whoami-redis -c db sh
kubectl exec -it whoami-redis -c app sh
  apk add curl busybox-extras # install telnet
  curl localhost:4567
  telnet localhost 6379
    dbsize
    KEYS *
    GET count
    quit
kubectl get pod/whoami-redis
kubectl get pod/whoami-redis -o yaml
kubectl get pod/whoami-redis -o jsonpath="{.spec.containers[0].name}"
kubectl get pod/whoami-redis -o jsonpath="{.spec.containers[*].name}"
kubectl describe pod/whoami-redis

다음 명령어로 정리한다.

kubectl delete -f ./

Replicaset

개념은 다음과 같다.

ReplicaSet -> Find pod by labels -> Create pod from template

기본 예제

# whoami-rs.yml

apiVersion: apps/v1beta2
kind: ReplicaSet
metadata:
  name: whoami-rs
spec:
  replicas: 1
  selector:
    matchLabels:
      type: app
      service: whoami
  template:
    metadata:
      labels:
        type: app
        service: whoami
    spec:
      containers:
      - name: whoami
        image: subicura/whoami:1
        livenessProbe:
          httpGet:
            path: /
            port: 4567

kubectl get pods --show-labels
kubectl label pod/whoami-rs-<xxxx> service-
kubectl label pod/whoami-rs-<xxxx> service=whoami
kubectl scale --replicas=3 -f whoami.yml

스케일 아웃 예제

# whoami-rs-scaled.yml

apiVersion: apps/v1beta2
kind: ReplicaSet
metadata:
  name: whoami-rs
spec:
  replicas: 4
  selector:
    matchLabels:
      type: app
      service: whoami
  template:
    metadata:
      labels:
        type: app
        service: whoami
    spec:
      containers:
      - name: whoami
        image: subicura/whoami:1
        livenessProbe:
          httpGet:
            path: /
            port: 4567

정리

kubectl delete -f ./

Deployment

Deployment using replicaset

기본 예제

# whoami-deploy.yml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: whoami-deploy
spec:
  replicas: 3
  selector:
    matchLabels:
      type: app
      service: whoami
  template:
    metadata:
      labels:
        type: app
        service: whoami
    spec:
      containers:
      - name: whoami
        image: subicura/whoami:1
        livenessProbe:
          httpGet:
            path: /
            port: 4567

kubectl set image deploy/whoami-deploy whoami=subicura/whoami:2
kubectl apply -f whoami-deploy.yml
kubectl get rs -w
kubectl describe deploy/whoami-deploy
kubectl rollout history -f whoami-deploy.yml
kubectl set image deploy/whoami-deploy whoami=subicura/whoami:1 --record=true
kubectl rollout history -f whoami-deploy.yml
kubectl rollout history -f whoami-deploy.yml --revision=2
kubectl rollout status deploy/whoami-deploy
kubectl rollout undo deploy/whoami-deploy
kubectl rollout undo deploy/whoami-deploy --to-revision=3

추가 예제

# whoami-deploy-strategy.yml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: whoami-deploy
spec:
  replicas: 3
  selector:
    matchLabels:
      type: app
      service: whoami
  minReadySeconds: 5
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  template:
    metadata:
      labels:
        type: app
        service: whoami
    spec:
      containers:
      - name: whoami
        image: subicura/whoami:1
        livenessProbe:
          httpGet:
            path: /
            port: 4567

kubectl describe deploy/whoami-deploy
kubectl set image deploy/whoami-deploy whoami=subicura/whoami:2
kubectl get rs -w

정리

kubectl delete -f ./

Service

StaticIP와 NodePort에 대해 실습한다.

기본 예제

# redis-app.yml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: redis
spec:
  selector:
    matchLabels:
      type: db
      service: redis
  template:
    metadata:
      labels:
        type: db
        service: redis
    spec:
      containers:
      - name: redis
        image: redis
        ports:
        - containerPort: 6379
          protocol: TCP
---

apiVersion: v1
kind: Service
metadata:
  name: redis
spec:
  ports:
  - port: 6379
    protocol: TCP
  selector:
    type: db
    service: redis

# whoami-deploy.yml

apiVersion: apps/v1beta2
kind: Deployment
metadata:
  name: whoami
spec:
  selector:
    matchLabels:
      type: app
      service: whoami
  template:
    metadata:
      labels:
        type: app
        service: whoami
    spec:
      containers:
      - name: whoami
        image: subicura/whoami-redis:1
        env:
        - name: REDIS_HOST
          value: "redis"
        - name: REDIS_PORT
          value: "6379"

kubectl get ep
kubectl exec -it whoami-<xxxxx> sh
  apk add curl busybox-extras # install telnet
  curl localhost:4567
  curl localhost:4567
  telnet localhost 6379
  telnet redis 6379
    dbsize
    KEYS *
    GET count
    quit

노드 포트

# whoami-svc.yml

apiVersion: v1
kind: Service
metadata:
  name: whoami
spec:
  type: NodePort
  ports:
  - port: 4567
    protocol: TCP
  selector:
    type: app
    service: whoami

정리

kubectl delete -f ./