A job in Kubernetes is a supervisor for pods carrying out batch processes, that is, a process that runs for a certain time to completion, for example a calculation or a backup operation.

Let’s create a job called countdown that supervises a pod counting from 9 down to 1:

$ kubectl apply -f https://raw.githubusercontent.com/openshift-evangelists/kbe/master/specs/jobs/job.yaml

You can see the job and the pod it looks after like so:

$ kubectl get jobs
NAME                      DESIRED   SUCCESSFUL   AGE
countdown                 1         1            5s

$ kubectl get pods --show-all
NAME                            READY     STATUS      RESTARTS   AGE
countdown-lc80g                 0/1       Completed   0          16s

To learn more about the status of the job, do:

$ kubectl describe jobs/countdown
Name:           countdown
Namespace:      default
Image(s):       centos:7
Selector:       controller-uid=ff585b92-2b43-11e7-b44f-be3e8f4350ff
Parallelism:    1
Completions:    1
Start Time:     Thu, 27 Apr 2017 13:21:10 +0100
Labels:         controller-uid=ff585b92-2b43-11e7-b44f-be3e8f4350ff
Pods Statuses:  0 Running / 1 Succeeded / 0 Failed
No volumes.
  FirstSeen     LastSeen        Count   From                    SubobjectPath   Type            Reason                  Message
  ---------     --------        -----   ----                    -------------   --------        ------                  -------
  2m            2m              1       {job-controller }                       Normal          SuccessfulCreate        Created pod: countdown-lc80g

And to see the output of the job via the pod it supervised, execute:

kubectl logs countdown-lc80g

To clean up, use the delete verb on the job object which will remove all the supervised pods:

$ kubectl delete job countdown
job "countdown" deleted

Note that there are also more advanced ways to use jobs, for example, by utilizing a work queue or scheduling the execution at a certain time via cron jobs.

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