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Job vs CronJob

Hands-on example​

Assume:

  • A working Kubernetes cluster
  • kubectl is configured

Initial state​

No Jobs or CronJobs exist.

kubectl get jobs
kubectl get cronjobs
No resources found in default namespace.
No resources found in default namespace.

Step 1: Create a Job​

Create a Job that runs once and exits.

kubectl apply -f - <<EOF
apiVersion: batch/v1
kind: Job
metadata:
  name: once-job
spec:
  template:
    spec:
      containers:
      - name: job
        image: busybox
        command: ["sh", "-c", "echo hello && sleep 2"]
      restartPolicy: Never
EOF
job.batch/once-job created

Check Pods.

kubectl get pods
once-job-abcde   0/1   Completed   0   10s

Check Job status.

kubectl get job once-job
NAME       COMPLETIONS   DURATION   AGE
once-job   1/1           2s         15s

What changed:

  • Job completed successfully

What did not change:

  • Job will not run again

Step 2: Create a CronJob​

Create a CronJob that runs every minute.

kubectl apply -f - <<EOF
apiVersion: batch/v1
kind: CronJob
metadata:
  name: repeat-job
spec:
  schedule: "*/1 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: job
            image: busybox
            command: ["sh", "-c", "date"]
          restartPolicy: Never
EOF
cronjob.batch/repeat-job created

Wait and check Jobs.

kubectl get jobs
NAME                 COMPLETIONS   AGE
repeat-job-28672001  1/1           10s
repeat-job-28672002  1/1           70s

What changed:

  • New Jobs are created on schedule

What did not change:

  • Each Job still runs only once

Key observation​

  • Jobs are one-time executions
  • CronJobs only schedule Job creation