Kubernetes Jobs and CronJobs Complete Guide

💡 Quick Answer: Create Kubernetes Jobs for one-time tasks and CronJobs for scheduled work. Covers parallelism, backoff limits, completion tracking, and time zones.

The Problem

This is one of the most searched Kubernetes topics. Having a comprehensive, well-structured guide helps both beginners and experienced users quickly find what they need.

The Solution

Create a Job

apiVersion: batch/v1
kind: Job
metadata:
  name: data-migration
spec:
  backoffLimit: 3               # Retry up to 3 times on failure
  activeDeadlineSeconds: 600    # Timeout after 10 minutes
  ttlSecondsAfterFinished: 3600 # Clean up after 1 hour
  template:
    spec:
      containers:
        - name: migrate
          image: my-app:v1
          command: ["python", "migrate.py"]
          env:
            - name: DATABASE_URL
              valueFrom:
                secretKeyRef:
                  name: db-secret
                  key: url
      restartPolicy: Never       # Required for Jobs

Parallel Jobs

apiVersion: batch/v1
kind: Job
metadata:
  name: process-queue
spec:
  parallelism: 5        # Run 5 pods simultaneously
  completions: 20       # Total tasks to complete
  backoffLimit: 3
  template:
    spec:
      containers:
        - name: worker
          image: worker:v1
      restartPolicy: Never

CronJob (Scheduled Jobs)

apiVersion: batch/v1
kind: CronJob
metadata:
  name: nightly-backup
spec:
  schedule: "0 2 * * *"         # 2 AM daily
  timeZone: "Europe/Paris"      # K8s 1.27+
  concurrencyPolicy: Forbid     # Don't overlap
  successfulJobsHistoryLimit: 3
  failedJobsHistoryLimit: 3
  startingDeadlineSeconds: 300  # Skip if >5min late
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: backup
              image: backup-tool:v1
              command: ["./backup.sh"]
          restartPolicy: OnFailure

Cron Schedule Reference

# Check jobs
kubectl get jobs
kubectl get cronjobs

# Manually trigger a CronJob
kubectl create job manual-backup --from=cronjob/nightly-backup

# Check job logs
kubectl logs job/data-migration

# Delete completed jobs
kubectl delete jobs --field-selector status.successful=1

graph TD
    A[CronJob] -->|Schedule triggers| B[Job created]
    B --> C[Pod 1 - working]
    B --> D[Pod 2 - working]
    B --> E[Pod 3 - working]
    C -->|Success| F[Complete]
    D -->|Failure| G{Retry?}
    G -->|backoffLimit not reached| H[New Pod]
    G -->|backoffLimit reached| I[Failed]

Frequently Asked Questions

What’s the difference between Job and CronJob?

A Job runs once and completes. A CronJob creates Jobs on a schedule (like cron on Linux). CronJobs are for recurring tasks.

Why use restartPolicy: Never vs OnFailure?

Never creates a new pod on failure (good for debugging — you can see logs). OnFailure restarts the same pod in-place.

Best Practices

• Start simple — use the basic form first, add complexity as needed
• Be consistent — follow naming conventions across your cluster
• Document your choices — add annotations explaining why, not just what
• Monitor and iterate — review configurations regularly

Key Takeaways

• This is fundamental Kubernetes knowledge every engineer needs
• Start with the simplest approach that solves your problem
• Use kubectl explain and kubectl describe when unsure
• Practice in a test cluster before applying to production