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