Jobs and CronJobs

Jobs

• Job: run workload until N successful completions; Pod stops when work finishes
• Completed Jobs/Pods not auto-deleted: delete manually or use ttlSecondsAfterFinished
• Pod template inside spec.template: same fields as Pod
• restartPolicy: only OnFailure or Never (not Always)

• backoffLimit: retries before failed (default 6)

Job YAML skeleton

apiVersion: batch/v1
kind: Job
metadata:
  name: counter
spec:
  completions: 1
  parallelism: 1
  backoffLimit: 6
  ttlSecondsAfterFinished: 100
  template:
    spec:
      restartPolicy: Never
      containers:
      - name: counter
        image: nginx:1.25.1
        command: ["/bin/sh", "-c", "echo done"]

CronJobs

• CronJob → creates Job → creates Pod on schedule
• spec.schedule: cron expression (* * * * * = every minute)
• spec.jobTemplate: Job template (not Pod directly)
• Default history: 3 successful Jobs, 1 failed Job retained

apiVersion: batch/v1
kind: CronJob
metadata:
  name: current-date
spec:
  schedule: "*/2 * * * *"
  successfulJobsHistoryLimit: 7
  failedJobsHistoryLimit: 3
  concurrencyPolicy: Forbid    # skip if previous still running
  jobTemplate:
    spec:
      template:
        spec:
          restartPolicy: OnFailure
          containers:
          - name: current-date
            image: nginx:1.25.1
            args: ["/bin/sh", "-c", 'echo $(date)']

Cron schedule shortcuts

kubectl

• kubectl create job <n> --image=<img> -- <cmd>
• kubectl get jobs: watch COMPLETIONS (e.g. 1/1)
• kubectl logs <pod-from-job>
• kubectl create cronjob <n> --schedule="* * * * *" --image=<img> -- <cmd>
• kubectl get cronjobs / kubectl get jobs,po
• kubectl create job <n> --from=cronjob/<cronjob>: trigger now

kubectl create cronjob backup \
  --image=busybox \
  --schedule="0 2 * * *" \
  -- sh -c 'echo backup'

kubectl create job backup-now --from=cronjob/backup
kubectl patch cronjob backup -p '{"spec":{"suspend":true}}'
kubectl patch cronjob backup -p '{"spec":{"suspend":false}}'

Key fields

Exam tips

• Job Pod restartPolicy must be OnFailure or Never
• CronJob Pods prefixed with CronJob name: use kubectl get jobs,po to trace
• Exam clusters use UTC for schedules unless stated otherwise
• If no Jobs appear, check .spec.suspend, schedule syntax, and describe cronjob