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All 30 stages in one place — filter by difficulty or verification status, or search. Click any row for the stage's concept note and the diff the reference solution adds at that stage.

  • 30Stages
  • 30✓ Verified
  • 10Hard
  • 1Course
What "verified" means: ✓ Verified — the stage has a reference solution checked in that passed stages 1..N cumulatively against a live kind cluster in CI. CI re-verifies every snapshot on each push, so a drifted assertion fails the build rather than the reader.
✓ Stage Level What it teaches
✓ 1. Find the cluster Easy Before a client can do anything it has to answer "which server, as whom?", and the answer is never hardcoded.▸
✓ 2. Choose a context Easy A context is a named triple: a cluster, a user, and optionally a namespace.▸
✓ 3. Ask the server what it is Medium This is the first request that leaves your machine, and it deliberately goes through the discovery client rather than a typed one.▸
✓ 4. List the pods Easy The first real read. A typed clientset gives you a method per resource — CoreV1().Pods(ns).List(...) — which returns *corev1.PodList with real Go fields.▸
✓ 5. Choose a namespace Medium Namespace resolution has three steps and the middle one is the trap: --namespace, then whatever the current context carries, then "default".▸
✓ 6. Print a table Medium A table is a user interface, and the property that makes it one is that the columns line up when the names do not.▸
✓ 7. Humanise the age Medium The API stores a creation timestamp; a person reading a hundred rows wants "2d".▸
✓ 8. Print the object as JSON Medium -o json is not "your table, as JSON". It is the API's own object, verbatim — apiVersion, kind, metadata, spec, status, managedFields and all.▸
✓ 9. Print the object as YAML Medium Same object, different serializer — and the way you get there matters.▸
✓ 10. Look everywhere at once Medium -A is not a client-side filter and it is not a loop over namespaces.▸
✓ 11. Ask for one object Easy Get and List are different endpoints with different failure modes, and the difference is the lesson. A List of an empty namespace succeeds and returns nothing.▸
✓ 12. Ask what the server serves Medium This is the request that makes a client general. Nothing in your program knows what a Pod is: the server reports its groups, the versions in each, and the resources in those —…▸
✓ 13. Resolve any spelling Hard po, pod, pods, Pod, pods.v1. — five spellings of one thing, and the API accepts exactly one of them in a URL.▸
✓ 14. Get anything at all Hard This is the largest single step in the course: your program stops being a pod client. The dynamic client speaks in GVRs and unstructured.▸
✓ 15. Wider columns Easy -o wide adds the columns that only make sense for a particular resource: a Pod's node and IP, a Service's cluster IP and ports.▸
✓ 16. Filter by label Medium Labels are the identifying metadata everything in Kubernetes coordinates through: a Service finds its pods by selector, a Deployment owns its ReplicaSets by selector.▸
✓ 17. Filter by field Medium Field selectors look like label selectors and are a different axis.▸
✓ 18. A stable order Easy The API returns items in whatever order the storage layer hands them over.▸
✓ 19. Keep watching Hard A watch is a long-lived HTTP response the server keeps appending to, one JSON event per change: ADDED, MODIFIED, DELETED, BOOKMARK, ERROR.▸
✓ 20. Delete an object Easy The first write, and the lesson is that delete is asynchronous. The call returns when the server has accepted the request and marked the object — not when it is gone.▸
✓ 21. Create from a manifest Hard A manifest is self-describing: it carries apiVersion and kind, which is why kubectl create -f needs no flag saying what is in the file.▸
✓ 22. Apply, not create Hard Apply is not "create if missing, update if present". It is a different claim: these fields should look like this, and I am the one saying so.▸
✓ 23. Two managers, one field Hard When your apply sets a field another manager already owns, the server answers 409 Conflict and changes nothing.▸
✓ 24. Change one field Medium Patch is the smallest write verb: the body names only what changes, so nothing has to be read first and there is no resourceVersion to conflict on.▸
✓ 25. Scale through a subresource Medium /scale is a subresource: a separate endpoint on the same object, with its own tiny schema.▸
✓ 26. Describe one object Medium Describe answers a different question from get, and the difference explains the format.▸
✓ 27. Attach its events Hard Events are the cluster's explanation of why, and the surprise is that they are not part of the object they describe.▸
✓ 28. Stream a container's logs Hard There is no Log object to Get. pods/log is a subresource that returns a stream of bytes, and with --follow it never ends — which is why its client-go signature could not have…▸
✓ 29. Run a command inside Hard Exec needs several independent byte streams at once — stdin, stdout, stderr and a terminal-resize channel — multiplexed over a single connection. Ordinary HTTP/1.▸
✓ 30. Forward a local port Hard Port-forward is the same upgrade as exec put to a different use: a local listener whose connections are tunnelled, one stream pair per forwarded port, through the apiserver to the…▸

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From the repo root: — it verifies every stage up to this one, so passing means nothing earlier broke.