[CKA][실습] 4. Application Lifecycle Management

Practice Test - Rolling Updates and Rollbacks

$ alias k=kubectl

## Deployment 배포 전략 확인
$ k describe deploy frontend
Name:                   frontend
Namespace:              default
CreationTimestamp:      Sat, 18 Feb 2023 07:02:45 +0000
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               name=webapp
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
StrategyType:           RollingUpdate


## Deployment 이미지 변경 명령어 옵션 확인
$ k set image -h
Update existing container image(s) of resources.

 Possible resources include (case insensitive):

  pod (po), replicationcontroller (rc), deployment (deploy), daemonset (ds), statefulset (sts),
cronjob (cj), replicaset (rs)

Examples:
  # Set a deployment's nginx container image to 'nginx:1.9.1', and its busybox container image to
'busybox'
  kubectl set image deployment/nginx busybox=busybox nginx=nginx:1.9.1
  
  # Update all deployments' and rc's nginx container's image to 'nginx:1.9.1'
  kubectl set image deployments,rc nginx=nginx:1.9.1 --all
  
  # Update image of all containers of daemonset abc to 'nginx:1.9.1'
  kubectl set image daemonset abc *=nginx:1.9.1
  
  # Print result (in yaml format) of updating nginx container image from local file, without hitting
the server
  kubectl set image -f path/to/file.yaml nginx=nginx:1.9.1 --local -o yaml
...

## Container 이름 확인
$ k get deploy frontend -o yaml
...
    spec:
      containers:
      - image: kodekloud/webapp-color:v1
        imagePullPolicy: IfNotPresent
        name: simple-webapp
...
## 이미지 변경
## 옵션 1
$ k set image deploy frontend simple-webapp=kodekloud/webapp-color:v2
## 옵션 2
$ k edit deploy frontend

---

Practice Test - Commands and Arguments

• Pod 시작 시 실행되는 명령어 확인

$ k get po ubuntu-sleeper -o yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-02-18T12:17:43Z"
  name: ubuntu-sleeper
  namespace: default
  resourceVersion: "785"
  uid: d1e21263-5e88-4167-8566-921649ab09a1
spec:
  containers:
  - command:
    - sleep
    - "4800"
    image: ubuntu

• 오류있는 yaml 파일 수정

$ k apply -f ubuntu-sleeper-3.yaml 
Error from server (BadRequest): error when creating "ubuntu-sleeper-3.yaml": Pod in version "v1" cannot be handled as a Pod: json: cannot unmarshal number into Go struct field Container.spec.containers.command of type string

## 수정 전
apiVersion: v1 
kind: Pod 
metadata:
  name: ubuntu-sleeper-3 
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
      - "sleep"
      - 1200
      
## 수정 후
apiVersion: v1 
kind: Pod 
metadata:
  name: ubuntu-sleeper-3 
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
      - sleep
      - "1200"

• command : 명령어, args : 명령어 전달 인자

apiVersion: v1 
kind: Pod 
metadata:
  name: webapp-green
  labels:
      name: webapp-green 
spec:
  containers:
  - name: simple-webapp
    image: kodekloud/webapp-color
    command: ["python", "app.py"]
    args: ["--color", "green"]