CKA每日一题 --- Day 1

今日考题

以下 Daemonset yaml 中，哪些是正确的？（多选）

yaml

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: default
  labels: k8s-app: fluentd-logging 
spec:
  selector:
    matchLabels:
      name: fluentd-elasticsearch
  template:
    metadata:
      labels:
        name: fluentd-elasticsearch
    spec:
      containers:
      - name: fluentd-elasticsearch
        image: gcr.io/fluentd-elasticsearch/fluentd:v2.5.1
        restartPolicy: Never

yaml

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: default
  labels:
    k8s-app: fluentd-logging
spec:
  selector:
    matchLabels:
      name: fluentd-elasticsearch
  template:
    metadata: 
      labels: name: fluentd-elasticsearch
    spec: 
      containers: 
      - name: fluentd-elasticsearch 
        image: gcr.io/fluentd-elasticsearch/fluentd:v2.5.1 
        restartPolicy: Onfailure

yaml

apiVersion: apps/v1 
kind: DaemonSet 
metadata: 
  name: fluentd-elasticsearch 
  namespace: default 
  labels: 
    k8s-app: fluentd-logging 
spec: 
  selector: 
    matchLabels: 
  name: fluentd-elasticsearch 
  template: 
    metadata: 
      labels: name: fluentd-elasticsearch 
    spec: 
      containers: 
      - name: fluentd-elasticsearch 
        image: gcr.io/fluentd-elasticsearch/fluentd:v2.5.1 
        restartPolicy: Always

yaml

apiVersion: apps/v1 
kind: DaemonSet 
metadata: 
  name: fluentd-elasticsearch 
  namespace: default 
  labels: 
    k8s-app: fluentd-logging 
spec: 
  selector: 
    matchLabels: 
      name: fluentd-elasticsearch 
  template: 
    metadata: 
      labels: 
        name: fluentd-elasticsearch 
    spec: 
      containers: 
      - name: fluentd-elasticsearch 
        image: gcr.io/fluentd-elasticsearch/fluentd:v2.5.1

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答案： C、D

在考试时，只允许有考试网站和k8s两个标签页。所以平常学习时，尽可能去找文档去学习，才是最权威的。熟悉 https://kubernetes.io/concepts/ 目录下的内容对考试通过非常有帮助。

https://kuboard.cn/learning/ 目录下提供了 https://kubernetes.io/concepts/ 目录下的中文翻译，可以对照着学习。

以这个问题为例，直接打开daemonset的说明文档，见以下链接：

https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/

A Pod Template in a DaemonSet must have a RestartPolicy equal to Always, or be unspecified, which defaults to Always. Daemonset里的pod Template下必须有RestartPolicy，如果没指定，会默认为Always

在 https://kuboard.cn 上也可以找到对应的中文内容：

https://kuboard.cn/learning/k8s-intermediate/workload/wl-daemonset/create.html

restartPolicy 字段，可选值为 Always、OnFailure 和 Never。默认为 Always。一个Pod中可以有多个容器，restartPolicy适用于Pod 中的所有容器。restartPolicy作用是，让kubelet重启失败的容器。

另外Deployment、Statefulset的restartPolicy也必须为Always，保证pod异常退出，或者健康检查 livenessProbe失败后由kubelet重启容器。https://kubernetes.io/zh/docs/concepts/workloads/controllers/deployment 或者 https://kuboard.cn/learning/k8s-intermediate/workload/wl-deployment

Job和CronJob是运行一次的pod，restartPolicy只能为OnFailure或Never，确保容器执行完成后不再重启。https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/ 或者 https://kuboard.cn/learning/k8s-intermediate/workload/wl-job/

实际考试以上机实操为主

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CKA每日一题 --- Day 1