RBAC Mental Model

Roles grant verbs on resources within a namespace; ClusterRoles can grant cluster-scoped or reusable permissions. Bindings connect subjects to roles. Permissions are additive - there is no deny rule. Distinguish get, list and watch; avoid wildcards; test with kubectl auth can-i including --as during design.

Analogy: Kubernetes is a thermostat, not a remote control. You declare the temperature; independent controllers measure reality and keep acting. Debugging means finding which sensor, rule or actuator prevents convergence.

Read the object as evidence

kubectl get RESOURCE NAME -n NAMESPACE -o yaml
kubectl describe RESOURCE NAME -n NAMESPACE
kubectl get events -n NAMESPACE --sort-by=.metadata.creationTimestamp
kubectl explain RESOURCE.spec

Do not memorize these as a ritual. The first command exposes desired and observed state, the second connects conditions and events, the third supplies a timeline, and the fourth checks the server's schema. Compare what the controller was asked to do with what it reports doing. Then test the narrowest hypothesis.

Scenario: A support account can list Secrets to diagnose Pods. Base64 values make that credential access. Create a narrower diagnostic role around Pods, logs and events.

Reduce permissions by observed operations

Model RBAC as subject plus verb plus resource plus scope. get reads one object, list reads collections, and watch streams changes; subresources such as pods/log and pods/exec require distinct grants. Test exact identities with kubectl auth can-i --list --as=... -n ... and review wildcard grants whenever APIs grow.

Scenario: A viewer can create Pods but cannot read Secrets. It creates a Pod mounting a privileged ServiceAccount token and escapes the intended boundary. Authorization review must consider privilege-escalation paths, not isolated verbs.
Warning: Kubernetes RBAC is additive. A narrow RoleBinding does not subtract permissions inherited from another binding; enumerate the subject's complete effective access.

Production reasoning

Ask four questions: Who owns this object? What dependency must become ready next? Which controller reports the blocking condition? What evidence would disprove my current theory? This prevents symptom-driven changes. Record the context, namespace, object generation, image digest and recent rollout before mutation; a recreated Pod may erase the evidence you needed.

Warning: Running is not the same as ready, healthy, durable or correct. Kubernetes status is layered. Confirm the application-level outcome as well as the object state.
Goal: Put this model into practice in the Kubernetes lab rbac-least-privilege. Open /labs/kubernetes, choose rbac-least-privilege, predict the failure path before changing anything, then use the simulator's check command to validate the finished state.

Deliberate practice

Before the lab, write the expected object relationship and the first three commands you will run. Afterward, explain why the fix converged and name one tempting change that would only mask the symptom. Repeat using an explicit namespace and a structured output format. This prediction-observation-explanation loop is what turns command familiarity into production judgment.

45-minute investigation

  1. Map (5 min): draw the owner-to-child chain and mark every namespace, selector, identity and dependency involved.
  2. Predict (5 min): write one expected status condition, one likely event and one log or metric signal before opening the lab.
  3. Observe (10 min): collect YAML, describe output and ordered events. Do not mutate state. Record which observation disproves your first theory.
  4. Repair (15 min): make the smallest declarative correction, watch the responsible controller converge, and verify the user-facing path rather than stopping at Running.
  5. Stress (10 min): change one relevant constraint - replica count, label, readiness, resource value or placement rule - predict the outcome, observe it, then restore the known-good declaration.
Tip: Keep a short incident note with symptom, evidence, hypothesis, change, result. Across four sections this produces a reusable runbook instead of a pile of remembered commands.