Break things safely.A hands-on Kubernetes simulator in your browser.
Hands-on simulators for developers. A real terminal onto a pretend system: deploy it, watch it fail, and fix it — before it happens at work.
Play a free missionCreate a free account
Free to use. 2 missions per simulator without an account — an account keeps your stars and XP.
🚨 PAGE: web — deploy by ci-bot is stuck. New pods are not starting. Customers are fine for now; the pipeline is blocked.$ kubectl get podsNAME READY STATUS RESTARTS AGENAME READY STATUSweb-7ssv97thnv-6bfzk 0/1 ImagePullBackOff 0 34sweb-7ssv97thnv-6bfzk 0/1 ImagePullBackOffweb-7ssv97thnv-g5fb9 0/1 ImagePullBackOff 0 34sweb-7ssv97thnv-g5fb9 0/1 ImagePullBackOffweb-7ssv97thnv-v4zhd 0/1 ImagePullBackOff 0 34sweb-7ssv97thnv-v4zhd 0/1 ImagePullBackOffweb-v66zlj9576-4zttz 1/1 Running 0 2d5hweb-v66zlj9576-4zttz 1/1 Runningweb-v66zlj9576-6h7m6 1/1 Running 0 2d5hweb-v66zlj9576-6h7m6 1/1 Runningweb-v66zlj9576-c8mkv 1/1 Running 0 2d5hweb-v66zlj9576-c8mkv 1/1 Runningweb-v66zlj9576-m92ms 1/1 Running 0 2d5hweb-v66zlj9576-m92ms 1/1 Runningweb-v66zlj9576-wxkfw 1/1 Running 0 2d5hweb-v66zlj9576-wxkfw 1/1 Running$ kubectl rollout undo deployment/webdeployment.apps/web rolled back$ kubectl rollout status deployment/webWaiting for deployment "web" rollout to finish: 5 out of 6 new replicas have been updated...Waiting for deployment "web" rollout to finish: 5 of 6 updated replicas are available...deployment "web" successfully rolled out
How it works
A real terminal
Type the commands you would type at work. The output matches the real tool, byte for byte — and anything we don't simulate says so.
Incidents, not quizzes
Each mission drops you into a broken system with a page going off. Any fix that works, passes: there is no one right answer to guess.
Nothing to install
It runs in your browser. Break it as badly as you like — reset, try again, and earn up to three stars a mission.
Simulators
Guides
The incidents the missions throw at you, and how to fix them on a real cluster.
- How to fix CrashLoopBackOff in Kubernetes
- ImagePullBackOff and ErrImagePull: causes and fixes
- OOMKilled (exit code 137): fixing out-of-memory pods
- Roll back a bad deployment with kubectl rollout undo
- Debugging NetworkPolicy: why pods can't reach each other
- Practising for the CKA and CKAD with a Kubernetes simulator