k8s 离线部署一个busybox，进而创建cronjob执行任务

• 首先创建一个yaml，创建一个名字是busybox-test的容器

  apiVersion: v1
  kind: Pod
  metadata:
  name: busybox-test
  labels:
  purpose: demonstrate-busybox
  spec:
  containers:
  - name: busybox
  image: busybox
  imagePullPolicy: IfNotPresent
  command:
  - sleep
  - "3600"
  resources:
  limits:
  memory: "128Mi"
  cpu: "500m"

• 然后拉取busybox的安装镜像（如果可以连上docker仓库则可以不需要下载）

  sudo docker pull busybox
  sudo docker save busybox -o busybox.tar
  

• 加载busybox镜像

  sudo ctr -n k8s.io images import busybox.tar

• 然后根据yaml启动busybox pod

  kubectl apply -f cronjob.yaml

• 此时busybox的pod已经运行起来了

  $ kubectl get pods
  NAME READY STATUS RESTARTS AGE
  busybox-test 1/1 Running 0 7m10s
  helloworld-nodejs-78c85f6bc8-kvrw6 1/1 Running 1 (5h15m ago) 3d5h
  helloworld-nodejs-78c85f6bc8-l9mxg 1/1 Running 1 (5h15m ago) 3d5h
  nginx-deployment-54b6f7ddf9-vcl6k 1/1 Running 3 (5h15m ago) 6d22h
  nginx-deployment-54b6f7ddf9-x6j7z 1/1 Running 3 (5h15m ago) 6d22h

• 可以进pod中执行一些命令

  $ kubectl exec -it busybox-test -- sh
  / # ps aux
  PID USER TIME COMMAND
  1 root 0:00 sleep 3600
  20 root 0:00 sh
  26 root 0:00 ps aux

然后可以将它拓展为一个cronjob的pod，定时运行，yaml改写成：

apiVersion: batch/v1
kind: CronJob
metadata:
  name: example-cronjob
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: example-container
            image: busybox
            imagePullPolicy: IfNotPresent
            args:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure

这个yaml的意思就是创建一个cronjob，然后每1分钟（schedule: "*/1 * * * *"）会创建一个busybox的pod执行"/bin/sh -c date; echo Hello from the Kubernetes cluster" 命令

• 可以通过下面命令看到cronjob的pods已经创建起来了

  $ kubectl get pods
  NAME READY STATUS RESTARTS AGE
  example-cronjob-28659390-fk9kq 0/1 Completed 0 2m15s
  example-cronjob-28659391-gbkps 0/1 Completed 0 75s
  example-cronjob-28659392-sxzzg 0/1 Completed 0 15s
  helloworld-nodejs-78c85f6bc8-kvrw6 1/1 Running 1 (5h29m ago) 3d5h
  helloworld-nodejs-78c85f6bc8-l9mxg 1/1 Running 1 (5h29m ago) 3d5h
  nginx-deployment-54b6f7ddf9-vcl6k 1/1 Running 3 (5h29m ago) 6d23h
  nginx-deployment-54b6f7ddf9-x6j7z 1/1 Running 3 (5h29m ago) 6d23h

  $ kubectl get cronjobs
  NAME SCHEDULE SUSPEND ACTIVE LAST SCHEDULE AGE
  example-cronjob */1 * * * * False 0 10s 8m22s

  $ kubectl get jobs
  NAME COMPLETIONS DURATION AGE
  example-cronjob-28659393 1/1 3s 2m38s
  example-cronjob-28659394 1/1 3s 98s
  example-cronjob-28659395 1/1 3s 38s

• 查看cronjob的输出， 可以看到yaml里面配置的内容：

  $ kubectl logs example-cronjob-28659396-mklws
  Fri Jun 28 08:36:00 UTC 2024
  Hello from the Kubernetes cluster

• 删除cronjob

  $ kubectl delete cronjobs example-cronjob
  cronjob.batch "example-cronjob" deleted