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cka-sim/weak-spots-cka.md
vumast3r 55ab18f814 fix: repair the CKA bank and harness after a live audit; add Simulator Set D 
Every changed task was seeded, graded untouched, solved and re-graded on a
separate kind cluster. The four sim sets were rehearsed as full sittings (real
baseline, seed everything, solve in order, grade at the end): A 150/150,
B 176/176, C 163/163, D 122/122. Every random-pool task was either passed in a
real session or cycled the same way.

Graders that could never pass, or passed for free:
  Q306 (local-path cannot resize; now graded as an in-place resize), Q314 (GNU
  grep prefixed file names), Q305 (plain `get events` has no SOURCE column and
  events expire; now managedFields), Q410 (kindnet DOES enforce NetworkPolicy;
  the expected answer is now derived from the CNI), Q35, Q212 (missing `]`),
  Q101 (`can-i create pods/exec` asks about a pod NAMED exec; multi-type get),
  Q109 (an emptyDir over nginx's /var/log crash-loops it), Q40 (TTL was
  measured at grading time), Q121, Q106, Q104, Q41, Q26, Q403, Q409, Q417,
  Q113, Q22, Q24/Q108 (flaky right after a rollout), and free points on
  untouched Q24/Q102/Q108/Q119/Q122.

Reference solutions: S[43], S[107], S[121], S[106] rewritten; S[116] (a
Completed Job pod still pins its PVC), S[119] (a pods quota equal to replicas
deadlocks the rollout); DNS checks use FQDNs; the explainer and exam guide
are corrected (etcd restore is etcdutl's job on 3.6+).

Cross-session leaks: the pre-session baseline now also repairs Q114 (the
kube-system NetworkPolicy and CoreDNS replicas), Q117/Q39 kubelet CA paths,
Q317, kubelet drop-in binary paths, a moved scheduler manifest, leftover
static pods and the default StorageClass. Q115 releases its fixed PVs from
claims left by earlier sessions.

Conflicts: `breaks` may be a list and `solo` keeps Q102's etcd restore out of
mixed sessions. Q118, Q5/Q103, Q26 vs the W1 taints, set A 203/204/208/212 and
set B 305/309 no longer sabotage each other. Q317 now disables only CSR
signing (the old break killed the whole controller-manager). Q110/Q311 no
longer compare against the whole cluster at submit time. Two delete/recreate
races in setups are fixed.

Harness: the weak list clears after two clean passes in a row, weak entries
show the latest attempt's failures, domain scores use the exam's own tasks,
history entries can be marked synthetic (entry 11 is), the web UI lists
every sim set, `./exam grade` refuses mid-exam (--force), preflight checks W1.

Set D (`./exam sim d`): 17 original killer.sh-style tasks, ids 501-517,
122 points - control-plane inventory, event forensics with crictl, a broken
kubelet unit, kubelet certificates, manual scheduling with the scheduler
stopped, Helm housekeeping with a stuck release, an enforced AND-vs-OR
NetworkPolicy, dnsPolicy and access-mode troubleshooting, and more.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-09-22 21:59:35 -06:00

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# CKA weak spots
_Generated by exam from 10 attempt(s); regenerated on every `end`._
## Domain scores (latest full exam, 2026-09-08T19:59, 14.3%)
- **ARCH** 12/26 — Cluster Architecture, Installation & Configuration (25%)
- **WORK** 1/16 — Workloads & Scheduling (15%)
- **NET** 0/17 — Services & Networking (20%)
- **STOR** 0/11 — Storage (10%)
- **TSHOOT** 2/35 — Troubleshooting (30%)
## Drill next (`./exam drill weak`)
### Q02 · ARCH · etcd snapshot (1/2 failed, last 0/7 pts, last failed 2026-09-19T12:27)
- ✗ /opt/cka/etcd-snapshot.db exists on the control-plane node
- ✗ snapshot is a real etcd backup (> 100 KB)
### Q06 · ARCH · Certificates: expiry check and user CSR (2/3 failed, last 6/6 pts, last failed 2026-09-12T22:17)
- passed last time (6/6) - one more clean pass takes it off this list
### Q15 · STOR · PersistentVolume, claim and pod (3/4 failed, last 6/6 pts, last failed 2026-09-15T20:55)
- passed last time (6/6) - one more clean pass takes it off this list
### Q16 · STOR · Default StorageClass and dynamic provisioning (4/4 failed, last 0/5 pts, last failed 2026-09-16T19:40)
- ✗ StorageClass fast-local: local-path, WaitForFirstConsumer, Delete
- ✗ fast-local is default and standard is not
- ✗ fast-claim picked up fast-local and is Bound
- ✗ fast-pod Running with claim at /data
### Q17 · TSHOOT · Node NotReady (3/4 failed, last 8/8 pts, last failed 2026-09-13T01:06)
- passed last time (8/8) - one more clean pass takes it off this list
### Q19 · TSHOOT · CrashLoopBackOff diagnosis (4/5 failed, last 6/6 pts, last failed 2026-09-14T16:49)
- passed last time (6/6) - one more clean pass takes it off this list
### Q28 · WORK · Init container prepares content (4/4 failed, last 0/4 pts, last failed 2026-09-16T19:40)
- ✗ pod Running, init container named setup completed
- ✗ emptyDir 'content' shared by both containers
- ✗ nginx serves the init-written content
### Q29 · WORK · Immutable ConfigMap rotation (3/4 failed, last 4/4 pts, last failed 2026-09-15T20:55)
- passed last time (4/4) - one more clean pass takes it off this list
### Q30 · NET · Named ports (2/3 failed, last 4/4 pts, last failed 2026-09-14T16:49)
- passed last time (4/4) - one more clean pass takes it off this list
### Q32 · WORK · ResourceQuota and LimitRange (1/1 failed, last 0/4 pts, last failed 2026-09-19T12:27)
- ✗ ResourceQuota limits pods/6, requests.cpu 1, limits.memory 2Gi
- ✗ LimitRange defaults set
- ✗ worker pods Running with defaulted requests
### Q33 · ARCH · Aggregated ClusterRole (2/3 failed, last 5/5 pts, last failed 2026-09-14T16:49)
- passed last time (5/5) - one more clean pass takes it off this list
### Q37 · TSHOOT · Cluster DNS is broken (4/5 failed, last 6/6 pts, last failed 2026-09-14T16:49)
- passed last time (6/6) - one more clean pass takes it off this list
### Q38 · TSHOOT · Deployments never create pods (2/3 failed, last 7/7 pts, last failed 2026-09-13T01:06)
- passed last time (7/7) - one more clean pass takes it off this list
### Q40 · ARCH · kubeadm join token (4/4 failed, last 0/5 pts, last failed 2026-09-16T19:40)
- ✗ join.sh contains a kubeadm join with token and CA hash
- ✗ the token in the file exists in the cluster with TTL ~24h
### Q42 · NET · Egress-only NetworkPolicy (2/3 failed, last 4/4 pts, last failed 2026-09-14T16:49)
- passed last time (4/4) - one more clean pass takes it off this list
### Q102 · ARCH · etcd restore (1/1 failed, last 2/10 pts, last failed 2026-09-19T12:27)
- ✗ ConfigMap restore-proof-67 exists again with its original data
- ✗ etcd uses a restored data directory (manifest changed)
### Q106 · ARCH · CRD with validation and defaults (4/4 failed, last 0/7 pts, last failed 2026-09-19T12:27)
- ✗ CRD exists, Namespaced, replicas has min/max and is required
- ✗ good created with environment prod
- ✗ replicas 0 is rejected and the message was saved
- ✗ defaulting works: defaulted.spec.environment == dev
### Q109 · WORK · Native sidecar with probes and an exact report (1/1 failed, last 2/8 pts, last failed 2026-09-19T12:27)
- ✗ native sidecar: initContainer agent with restartPolicy Always
- ✗ probes on app as specified
- ✗ Running, shared log written by agent, grace period 5
### Q112 · NET · TLS Ingress with a generated certificate (4/4 failed, last 0/7 pts, last failed 2026-09-19T12:27)
- ✗ Secret secure.lab.local-tls is kubernetes.io/tls with CN secure.lab.local
- ✗ Ingress web: class nginx, host, TLS secret, ssl-redirect annotation
- ✗ fp.txt matches the secret's certificate fingerprint
### Q115 · STOR · Bind the right local volume (3/3 failed, last 1/6 pts, last failed 2026-09-15T20:55)
- ✗ PVC uses a selector and is Bound to lv-nvme
- ✗ consumer Running on the nvme node with /data mounted
### Q120 · TSHOOT · Cluster facts, exactly (3/3 failed, last 0/5 pts, last failed 2026-09-15T20:55)
- ✗ pod-cidr and service-cidr
- ✗ dns-ip and proxy-mode
- ✗ cka-sim-worker3 pod CIDR
### Q121 · WORK · The context's namespace (3/3 failed, last 1/6 pts, last failed 2026-09-15T20:55)
- ✗ Deployment ledger-21 in ac-echo (the context's namespace), 2 available, owner=ac
- ✗ Service ledger-21 port 9000 in the same namespace
- ✗ ns.txt has the namespace
### Q202 · ARCH · Helm chart with CRDs, then a custom resource (1/1 failed, last 3/8 pts, last failed 2026-09-19T12:27)
- ✗ watchAllNamespaces=true reached the pod env
- ✗ Ledger main-ledger has currency USD and retentionDays 30
### Q204 · WORK · Which Pods get evicted first (1/1 failed, last 0/8 pts, last failed 2026-09-19T12:27)
- ✗ evicted-first.txt lists exactly the BestEffort pods
- ✗ api-qos.txt says Burstable
- ✗ guaranteed.txt names orion-ledger
### Q217 · TSHOOT · Inspect a container with crictl (1/1 failed, last 0/10 pts, last failed 2026-09-19T12:27)
- ✗ Pod tiger-probe Running with both labels
- ✗ container.txt holds a real container ID for that Pod
- ✗ container.txt records the runtimeType
- ✗ container.log holds the httpd startup output
### Q313 · NET · Two hosts, TLS, and a default backend (1/1 failed, last 0/11 pts, last failed 2026-09-19T12:27)
- ✗ Secret classic-tls is a TLS secret with CN classic.r700.io
- ✗ both host rules route to the right Services on /
- ✗ TLS covers both hosts with classic-tls
- ✗ defaultBackend points at web-classic:80, class is nginx
## Attempt matrix
| Q | Domain | Title | D1 | E2 | D3 | D4 | D5 | D6 | D7 | D8 | D9 | D10 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | ARCH | RBAC for a deployment bot | 2/6 | · | · | ✓ | · | · | · | · | · | · |
| 2 | ARCH | etcd snapshot | · | ✓ | · | · | · | · | · | · | · | 0/7 |
| 3 | ARCH | Kustomize overlay | · | 0/5 | · | · | · | · | ✓ | · | · | · |
| 4 | ARCH | CustomResourceDefinition | · | ✓ | · | · | · | · | · | · | · | ✓ |
| 5 | ARCH | Static pod | 0/5 | · | · | · | · | · | ✓ | · | · | · |
| 6 | ARCH | Certificates: expiry check and user CSR | 0/6 | · | · | 3/6 | · | · | ✓ | · | · | · |
| 7 | WORK | Rolling update & scaling | · | · | · | · | · | · | · | · | · | · |
| 8 | WORK | Multi-container pod with shared volume | · | 0/4 | · | · | · | · | ✓ | · | · | ✓ |
| 9 | WORK | Scheduling with node affinity and resources | · | · | · | · | · | · | · | · | · | ✓ |
| 10 | WORK | ConfigMap and Secret consumption | · | · | · | · | · | · | · | · | · | · |
| 11 | NET | NetworkPolicy | · | · | · | · | · | · | · | · | · | · |
| 12 | NET | NodePort Service | · | 0/4 | · | · | · | · | ✓ | · | · | · |
| 13 | NET | Ingress routing | · | 0/5 | · | · | · | · | 0/5 | ✓ | · | ✓ |
| 14 | NET | Cluster DNS | · | · | · | · | · | · | · | · | · | · |
| 15 | STOR | PersistentVolume, claim and pod | · | 0/6 | · | · | · | · | 0/6 | 0/6 | ✓ | · |
| 16 | STOR | Default StorageClass and dynamic provisioning | · | 0/5 | · | · | · | · | 0/5 | 0/5 | 0/5 | · |
| 17 | TSHOOT | Node NotReady | · | 0/8 | · | · | 4/8 | 4/8 | ✓ | · | · | · |
| 18 | TSHOOT | Broken deployment and service | · | 0/7 | · | · | · | · | ✓ | · | · | · |
| 19 | TSHOOT | CrashLoopBackOff diagnosis | · | 1/6 | · | · | 1/6 | 1/6 | 4/6 | ✓ | · | · |
| 20 | TSHOOT | Control plane component failure | · | 0/8 | · | · | · | · | ✓ | · | · | · |
| 21 | ARCH | Helm release install and upgrade | · | · | · | ✓ | · | · | · | · | · | · |
| 22 | NET | Gateway API HTTPRoute | · | · | · | · | · | · | · | · | · | · |
| 23 | WORK | metrics-server repair and HPA | · | · | · | · | · | · | · | · | · | · |
| 24 | WORK | PriorityClass | · | · | · | · | · | · | · | · | · | · |
| 25 | WORK | Taints and tolerations | · | 0/4 | · | · | · | · | 0/4 | 0/4 | ✓ | ✓ |
| 26 | WORK | DaemonSet on every node | · | · | · | · | · | · | · | · | · | · |
| 27 | WORK | CronJob with a manual run | · | · | · | · | · | · | · | · | · | · |
| 28 | WORK | Init container prepares content | · | 0/4 | · | · | · | · | 0/4 | 0/4 | 0/4 | · |
| 29 | WORK | Immutable ConfigMap rotation | · | 1/4 | · | · | · | · | 1/4 | 1/4 | ✓ | · |
| 30 | NET | Named ports | · | 0/4 | · | · | · | · | 0/4 | ✓ | · | · |
| 31 | WORK | Parallel Job | · | · | · | · | · | · | · | · | · | · |
| 32 | WORK | ResourceQuota and LimitRange | · | · | · | · | · | · | · | · | · | 0/4 |
| 33 | ARCH | Aggregated ClusterRole | · | 1/5 | · | · | · | · | 1/5 | ✓ | · | · |
| 34 | ARCH | Discover a CRD field with kubectl explain | 0/4 | · | · | ✓ | · | · | · | · | · | ✓ |
| 35 | STOR | Re-bind a Released PersistentVolume | · | · | · | · | · | · | · | · | · | · |
| 36 | STOR | Data survives the pod | · | · | · | · | · | · | · | · | · | · |
| 37 | TSHOOT | Cluster DNS is broken | · | 1/6 | · | · | 1/6 | 1/6 | 1/6 | ✓ | · | · |
| 38 | TSHOOT | Deployments never create pods | · | · | · | · | 0/7 | 0/7 | ✓ | · | · | · |
| 39 | TSHOOT | kubelet misconfiguration | · | · | · | · | 4/7 | 4/7 | 0/7 | ✓ | · | ✓ |
| 40 | ARCH | kubeadm join token | · | 0/5 | · | · | · | · | 0/5 | 0/5 | 0/5 | · |
| 41 | ARCH | Component versions | 0/4 | · | · | ✓ | · | · | · | · | · | · |
| 42 | NET | Egress-only NetworkPolicy | · | 0/4 | · | · | · | · | 0/4 | ✓ | · | · |
| 43 | NET | Headless and ExternalName services | · | · | · | · | · | · | · | · | · | · |
| 101 | ARCH | Exact RBAC with an existing over-grant | · | · | · | · | · | · | · | · | · | · |
| 102 | ARCH | etcd restore | · | · | · | · | · | · | · | · | · | 2/10 |
| 103 | ARCH | Static pod on a relocated manifest path | · | · | · | · | · | · | · | · | · | · |
| 104 | ARCH | User onboarding to a working kubeconfig | · | · | · | · | · | · | · | · | · | · |
| 105 | ARCH | Kustomize with generators and patches | · | · | · | · | · | · | · | · | · | · |
| 106 | ARCH | CRD with validation and defaults | · | · | 0/7 | · | · | · | 0/7 | 0/7 | · | 0/7 |
| 107 | WORK | Spread, tolerate, prioritise — under a quota | · | · | · | · | · | · | · | · | · | · |
| 108 | WORK | Rollback to a specific revision, then pause | · | · | · | · | · | · | · | · | · | · |
| 109 | WORK | Native sidecar with probes and an exact report | · | · | · | · | · | · | · | · | · | 2/8 |
| 110 | WORK | Namespace audit to exact files | · | · | · | · | · | · | · | · | · | · |
| 111 | NET | Zero-trust namespace | · | · | · | · | · | · | · | · | · | · |
| 112 | NET | TLS Ingress with a generated certificate | · | · | 0/7 | · | · | · | 0/7 | 0/7 | · | 0/7 |
| 113 | NET | Gateway API canary with header match | · | · | · | · | · | · | · | · | · | · |
| 114 | NET | DNS down: three faults | · | · | · | · | · | · | · | · | · | · |
| 115 | STOR | Bind the right local volume | · | · | 1/6 | · | · | · | 1/6 | 1/6 | · | · |
| 116 | STOR | Migrate data between claims | · | · | · | · | · | · | · | · | · | · |
| 117 | TSHOOT | Worker node: three things wrong | · | · | · | · | · | · | · | · | · | · |
| 118 | TSHOOT | Two control-plane components down | · | · | · | · | · | · | · | · | · | · |
| 119 | TSHOOT | Application down for four reasons | · | · | · | · | · | · | · | · | · | · |
| 120 | TSHOOT | Cluster facts, exactly | · | · | 0/5 | · | · | · | 0/5 | 0/5 | · | · |
| 121 | WORK | The context's namespace | · | · | 1/6 | · | · | · | 1/6 | 1/6 | · | · |
| 122 | ARCH | Renew control-plane certificates | · | · | · | · | · | · | · | · | · | · |
| 123 | TSHOOT | Nothing works: kube-apiserver itself is down | · | · | · | · | · | · | · | · | · | · |
| 124 | ARCH | Prepare a node join without shell access to the control plane | · | · | · | · | · | · | · | · | · | · |
| 201 | ARCH | kubeconfig forensics | · | · | · | · | · | · | · | · | · | · |
| 202 | ARCH | Helm chart with CRDs, then a custom resource | · | · | · | · | · | · | · | · | · | 3/8 |
| 203 | WORK | Find the controller, then scale it | · | · | · | · | · | · | · | · | · | · |
| 204 | WORK | Which Pods get evicted first | · | · | · | · | · | · | · | · | · | 0/8 |
| 205 | ARCH | Kustomize: drop a ConfigMap, add an HPA, override in prod | · | · | · | · | · | · | · | · | · | · |
| 206 | STOR | PV, PVC and a Deployment that mounts it | · | · | · | · | · | · | · | · | · | · |
| 207 | TSHOOT | Resource usage scripts | · | · | · | · | · | · | · | · | · | · |
| 208 | ARCH | Drain a node for maintenance | · | · | · | · | · | · | · | · | · | · |
| 209 | ARCH | Query the API from inside a Pod | · | · | · | · | · | · | · | · | · | · |
| 210 | ARCH | ServiceAccount limited to two resources | · | · | · | · | · | · | · | · | · | · |
| 211 | WORK | DaemonSet on every node | · | · | · | · | · | · | · | · | · | · |
| 212 | WORK | One Pod per node, on purpose | · | · | · | · | · | · | · | · | · | · |
| 213 | NET | Convert an Ingress to Gateway API, then split on a header | · | · | · | · | · | · | · | · | · | · |
| 214 | ARCH | Certificate expiry, two ways | · | · | · | · | · | · | · | · | · | · |
| 215 | NET | Egress policy with paired destinations | · | · | · | · | · | · | · | · | · | · |
| 216 | NET | CoreDNS: back up, extend, verify | · | · | · | · | · | · | · | · | · | · |
| 217 | TSHOOT | Inspect a container with crictl | · | · | · | · | · | · | · | · | · | 0/10 |
| 301 | ARCH | etcd configuration facts | · | · | · | · | · | · | · | · | · | ✓ |
| 302 | NET | Service rules on the node | · | · | · | · | · | · | · | · | · | · |
| 303 | NET | A second Service CIDR | · | · | · | · | · | · | · | · | · | · |
| 304 | ARCH | Bound tokens versus legacy tokens | · | · | · | · | · | · | · | · | · | · |
| 305 | WORK | Schedule without the scheduler | · | · | · | · | · | · | · | · | · | · |
| 306 | STOR | Grow a volume in place | · | · | · | · | · | · | · | · | · | · |
| 307 | TSHOOT | Node accepts nothing new | · | · | · | · | · | · | · | · | · | · |
| 308 | ARCH | API resource reference card | · | · | · | · | · | · | · | · | · | · |
| 309 | WORK | A PodDisruptionBudget that blocks maintenance | · | · | · | · | · | · | · | · | · | · |
| 310 | NET | Route to something outside the cluster | · | · | · | · | · | · | · | · | · | · |
| 311 | ARCH | Image inventory across the cluster | · | · | · | · | · | · | · | · | · | · |
| 312 | WORK | A Job that fails, then one that doesn't | · | · | · | · | · | · | · | · | · | · |
| 313 | NET | Two hosts, TLS, and a default backend | · | · | · | · | · | · | · | · | · | 0/11 |
| 314 | TSHOOT | A static pod that never starts | · | · | · | · | · | · | · | · | · | · |
| 315 | STOR | Keep the data when the claim goes | · | · | · | · | · | · | · | · | · | · |
| 316 | ARCH | Plan a control-plane upgrade | · | · | · | · | · | · | · | · | · | · |
| 317 | TSHOOT | Certificates stop being issued | · | · | · | · | · | · | · | · | · | · |
| 401 | STOR | Provision geo-fence persistent storage | · | · | · | · | · | · | · | · | · | · |
| 402 | ARCH | Render a chart, then install it | · | · | · | · | · | · | · | · | · | · |
| 403 | TSHOOT | Fix the driver onboarding app | · | · | · | · | · | · | · | · | · | · |
| 404 | NET | Expose and verify the dispatch API | · | · | · | · | · | · | · | · | · | · |
| 405 | STOR | Migrate ride history to a Retain volume | · | · | · | · | · | · | · | · | · | · |
| 406 | TSHOOT | Fix ETA service connectivity | · | · | · | · | · | · | · | · | · | · |
| 407 | NET | Fleet dashboard canary with Gateway API | · | · | · | · | · | · | · | · | · | · |
| 408 | ARCH | Cluster-wide read access for the auth team | · | · | · | · | · | · | · | · | · | · |
| 409 | WORK | Add an init container to the trip logger | · | · | · | · | · | · | · | · | · | · |
| 410 | NET | Audit the CNI, then lock a namespace down | · | · | · | · | · | · | · | · | · | · |
| 411 | WORK | Priority for the rider support portal | · | · | · | · | · | · | · | · | · | · |
| 412 | WORK | Surge pricing configuration | · | · | · | · | · | · | · | · | · | · |
| 413 | ARCH | Plan the control-plane upgrade | · | · | · | · | · | · | · | · | · | · |
| 414 | TSHOOT | Fix the fare calculation pods | · | · | · | · | · | · | · | · | · | · |
| 415 | WORK | Autoscale the route planner on memory | · | · | · | · | · | · | · | · | · | · |
| 416 | NET | NetworkPolicy for the safety monitor | · | · | · | · | · | · | · | · | · | · |
| 417 | ARCH | Enforce TLS 1.3 on the booking portal | · | · | · | · | · | · | · | · | · | · |
| 418 | TSHOOT | Investigate vehicle tracker health | · | · | · | · | · | · | · | · | · | · |
_E = full exam, D = drill, · = not in that session, n/m = partial credit._
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