Module 3: Container Orchestration: Mistake Clinic

This clinic turns wrong moves into reusable judgment. Use it after each practice page and again before the quiz or checkpoint.

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Module-Specific Mistake Radar

Start with these traps. Replace or extend them with real mistakes from your own work.

Mistake to look for	Where it shows up	Symptom	Repair evidence
Finishing Container Fundamentals Lab with only a final answer	Container Fundamentals Lab	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Kubernetes Primitives Workshop with only a final answer	Kubernetes Primitives Workshop	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Services and Storage Clinic with only a final answer	Services and Storage Clinic	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing K8s Katas with only a final answer	K8s Katas	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Treating Namespaces and Cgroups: The Two Kernel Features Behind Containers as vocabulary instead of a tool	Namespaces and Cgroups: The Two Kernel Features Behind Containers	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.
Treating OCI Images, Layers, and the Runtime as vocabulary instead of a tool	OCI Images, Layers, and the Runtime	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.

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Practice Mistake Checks

Pull any miss from these checks into your mistake log.

Container Fundamentals Lab

Source: practice/01-container-fundamentals-lab.md

For each statement, identify the error:

1. "A container is a lightweight VM because it isolates the kernel."
2. "I squashed my Dockerfile to one layer to make it smaller."
3. "Secrets in a ConfigMap are fine because they're in etcd."
4. "latest is the most recent version of this image."
5. "cgroups stop a compromised container from escaping."

Kubernetes Primitives Workshop

Source: practice/02-kubernetes-primitives-workshop.md

For each, identify the error:

1. "I ran kubectl delete pod and it restarted itself, so the cluster must have a bug."
2. "I edited status.replicas directly to force it."
3. "A Deployment with replicas: 3 gives me high availability."
4. "If I apply the same YAML again, nothing happens, so the apply must be idempotent in all cases."
5. "I scaled the ReplicaSet directly instead of the Deployment; it's the same thing."

Services and Storage Clinic

Source: practice/03-services-and-storage-clinic.md

For each, identify the error:

1. "My Service has no endpoints because the selector is wrong." (Is that always the reason?)
2. "I'll just use Ingress; I don't need to install anything."
3. "ReadWriteOnce means one Pod at a time can mount the volume."
4. "Deleting a PVC deletes the disk."
5. "A StatefulSet gives me automatic database failover."

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Repair Protocol

For each real mistake:

1. Reproduce the failure on the smallest example, trace, proof, query, command, or design sketch.
2. Name the hidden assumption.
3. Repair the artifact.
4. Save evidence that changed: failing then passing test, corrected proof step, revised diagram, safer command, benchmark, or review note.
5. Add one retrieval card beginning with Check... before... or Do not use... when....

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Mistake Log

Date	Mistake	Symptom	Root cause	Repair evidence	Retrieval card
Starter	Pick one radar row above	Explain how it would fail in this module	Name the assumption	Add a counterexample or corrected artifact	Write the card before closing the page

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Completion Standard

• At least five real mistakes are logged.
• At least two mistakes include a counterexample or failing test.
• At least one mistake connects to an older semester skill.
• At least one correction changes code, a proof, a diagram, a command transcript, a query, or a design decision.