vumast3r e07ee1beab refactor: CKA_SOLUTIONS_EXPLAINED.md + 12 files

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CKAD study guide

The 24 objectives of the Certified Kubernetes Application Developer curriculum, in its own words and order: what to know, the fastest commands, the traps, the documentation pages the exam lets you open, and the tasks in this simulator that practise each one.

Generated by ./exam --track ckad notes all --md from tracks/ckad/curriculum.py - edit that file, not this one.

./exam objectives        # the path and your progress
./exam study 3.2         # one objective: these notes, then its tasks, no clock, solutions open
./exam drill 3.2         # the same tasks against the clock

Application Design and Build (20%)

1.1 Define, build and modify container images

./exam study 1.1 (or images)

Know

Read and change a Dockerfile: FROM, COPY, RUN, ENV, ARG (build time only), WORKDIR, USER, LABEL, EXPOSE, ENTRYPOINT, CMD.
ENTRYPOINT is the program, CMD its default arguments. In a Pod, command replaces ENTRYPOINT and args replaces CMD.
Build, tag, list, inspect, run, save and remove images. The exam terminal has docker or podman - the verbs are the same.
A tag is only a pointer: one image can carry several tags, and rebuilding under an old tag moves it.

Fast

podman build -t localhost/app:v1 .                      # -f path/Dockerfile   --build-arg KEY=val
podman tag localhost/app:v1 localhost/app:latest
podman images | grep app
podman inspect localhost/app:v1 --format '{{.Config.User}} {{.Config.Entrypoint}} {{.Config.Cmd}} {{.Config.Env}}'
podman run --rm localhost/app:v1 [args replacing CMD]   # -d --name x keeps it running; podman logs x
podman save --format oci-archive -o app.tar localhost/app:v1     # docker save -o app.tar ...
podman rmi localhost/app:v0

Traps

An ARG is gone at run time unless you copy it into an ENV (ARG V then ENV APP_VERSION=$V).
podman save writes a docker-archive unless you pass --format oci-archive.
Build before you edit when a task wants the old version kept under its own tag.
imagePullPolicy defaults to Always for :latest (or no tag) and IfNotPresent for any other tag.

Docs

Tasks

Q13 Build, change and export a container image
Q60 Entrypoint, default argument and a non-root user
Q41 Build with a build argument, run it detached (Simulator Set A (killer.sh-style))

1.2 Choose and use the right workload resource (Deployment, DaemonSet, CronJob, etc.)

./exam study 1.2 (or workloads)

Know

Choose by behaviour: Deployment (interchangeable replicas, rolling updates), StatefulSet (stable name, DNS and storage per replica), DaemonSet (one Pod per node), Job (run to completion), CronJob (Jobs on a schedule), bare Pod (one-off).
Job: completions, parallelism, backoffLimit, activeDeadlineSeconds, ttlSecondsAfterFinished; restartPolicy must be Never or OnFailure.
CronJob: schedule, startingDeadlineSeconds, concurrencyPolicy (Allow, Forbid, Replace), suspend, successfulJobsHistoryLimit, failedJobsHistoryLimit.
DaemonSet: no replicas; a toleration for node-role.kubernetes.io/control-plane:NoSchedule puts it on control-plane nodes too.

Fast

k create deploy web --image=nginx:1.27 --replicas=3 $do > deploy.yaml
k create job render --image=busybox:1.36 $do -- sh -c 'echo done' > job.yaml
k create cronjob digest --image=busybox:1.36 --schedule='*/5 * * * *' $do -- sh -c 'echo digest' > cj.yaml
k create job digest-manual --from=cronjob/digest      # run a CronJob once, now
k run tmp --image=busybox:1.36 --restart=Never --rm -it -- sh
# DaemonSet has no generator: create a Deployment with $do, change kind, delete replicas/strategy/status
k explain cronjob.spec.jobTemplate.spec --recursive | less

Traps

Three nested specs in a CronJob: spec (schedule, startingDeadlineSeconds) > jobTemplate.spec (completions, activeDeadlineSeconds) > template.spec (containers, restartPolicy).
A Job's Pod template is immutable - delete the Job and create it again instead of editing it.
A StatefulSet needs serviceName naming a headless Service (clusterIP: None) before its Pods get their own DNS names.

Docs

Tasks

Q3 CronJob with deadlines
Q14 Parallel batch Job
Q15 DaemonSet on every node
Q39 A suspended CronJob and a manual run (Simulator Set A (killer.sh-style))
Q38 A Pod and a status one-liner (Simulator Set A (killer.sh-style))
Q44 From a single Pod to a hardened Deployment (Simulator Set A (killer.sh-style))
Q56 Stable DNS names for a StatefulSet (Simulator Set A (killer.sh-style))

1.3 Understand multi-container Pod design patterns (e.g. sidecar, init and others)

./exam study 1.3 (or multicontainer)

Know

Containers of a Pod share its network (they reach each other on localhost) and any volume both mount - that is all a sidecar, adapter or ambassador is.
Init containers run one at a time, in order, each to completion, before any app container starts.
A native sidecar is an init container with restartPolicy: Always: it starts before the app containers, keeps running beside them, and does not keep a Job from completing.
Address one container with -c: k logs POD -c NAME, k exec POD -c NAME -- .... Status Init:0/1 means an init container is still running.

Fast

k run app --image=nginx:1.27 $do > pod.yaml           # then add the second container by hand
spec:
  initContainers:
    - {name: wait, image: busybox:1.36, command: [sh, -c, "until wget -qO- -T2 http://backend; do sleep 2; done"]}
    - {name: shipper, image: busybox:1.36, restartPolicy: Always, command: [sh, -c, "tail -F /logs/app.log"],
       volumeMounts: [{name: logs, mountPath: /logs}]}                      # native sidecar
  containers:
    - {name: app, image: nginx:1.27, volumeMounts: [{name: logs, mountPath: /var/log/app}]}
  volumes: [{name: logs, emptyDir: {}}]
k logs app -c shipper;  k logs app --all-containers --prefix

Traps

kubectl run creates one container only - generate the Pod and add the others in the YAML.
A Service with no endpoints still resolves in DNS, so an init container waiting on nslookup is not waiting for the app. Wait on a real request.
A classic sidecar that never exits keeps a Job running for ever; make it a native sidecar.

Docs

Tasks

Q1 Adapter sidecar
Q2 Init container waits for a dependency
Q16 Native sidecar lets a Job finish
Q40 An init container writes the page (Simulator Set A (killer.sh-style))

1.4 Utilize persistent and ephemeral volumes

./exam study 1.4 (or volumes)

Know

Ephemeral: emptyDir (lives as long as the Pod; medium: Memory is tmpfs, sizeLimit caps it), and the configMap, secret, downwardAPI and projected volumes.
Persistent: a PersistentVolumeClaim asks for storage (accessModes, resources.requests.storage, storageClassName); a StorageClass provisions the PersistentVolume, or a pre-made one binds.
Access modes: ReadWriteOnce, ReadOnlyMany, ReadWriteMany, ReadWriteOncePod.
volumeMounts: mountPath, readOnly, and subPath to mount one file or directory without hiding the rest of the target directory.

Fast

apiVersion: v1
kind: PersistentVolumeClaim
metadata: {name: data}
spec:
  accessModes: [ReadWriteOnce]
  storageClassName: standard
  resources: {requests: {storage: 100Mi}}
---                                                    # in the Pod spec:
volumes:
  - {name: data, persistentVolumeClaim: {claimName: data}}
  - {name: scratch, emptyDir: {medium: Memory, sizeLimit: 32Mi}}
containers:
  - volumeMounts: [{name: data, mountPath: /data}, {name: scratch, mountPath: /scratch}]
k get pvc,pv;  k describe pvc data                     # Pending? the Events say why

Traps

There is no kubectl create pvc - copy the claim from the docs.
With a WaitForFirstConsumer StorageClass (standard here) a claim stays Pending until a Pod uses it. That is not an error.
emptyDir survives a container restart but not a new Pod. To prove data persists, delete the Pod and read the file again.
A non-root container cannot write to a fresh volume unless the Pod sets securityContext.fsGroup.

Docs

Tasks

Q17 Persistent and ephemeral volumes
Q10 Projected volume: config, secret and token
Q52 Two users, one volume: fsGroup (Simulator Set A (killer.sh-style))
Q40 An init container writes the page (Simulator Set A (killer.sh-style))
Q50 An immutable Secret, one file into a busy directory (Simulator Set A (killer.sh-style))

Application Deployment (20%)

2.1 Use Kubernetes primitives to implement common deployment strategies (e.g. blue/green or canary)

./exam study 2.1 (or strategies)

Know

Blue/green: two Deployments, and the Service selector decides which one gets all the traffic. Cut over by changing the selector; roll back by changing it back.
Canary: two Deployments whose Pods share the label the Service selects. Traffic splits by the number of ready Pods: 1 canary beside 4 stable is 20%.
A Deployment's own strategy is RollingUpdate (default) or Recreate (every old Pod stops first - downtime).

Fast

k get svc web -o wide;  k get pods --show-labels
k set selector svc web 'app=web,version=green'           # blue/green cut-over
k scale deploy web-stable --replicas=4                    # canary ratio: 4 stable + 1 canary = 20%
k get endpointslices -l kubernetes.io/service-name=web -o wide
k get pods -l app=web -L version,track

Traps

Wait until the new Deployment is fully available before you switch the selector.
kubectl set selector replaces the whole selector - name every label you want in it.
A canary only shares traffic if the Service selector leaves out the label that tells the two versions apart.

Docs

Tasks

Q5 Blue/green cutover
Q18 Canary by replica ratio

2.2 Understand Deployments and how to perform rolling updates

./exam study 2.2 (or rollouts)

Know

Any change to spec.template starts a rollout: a new ReplicaSet scales up while the old one scales down, within maxSurge and maxUnavailable (25% each by default).
minReadySeconds (how long a Pod must be Ready to count as available), revisionHistoryLimit (old ReplicaSets kept), progressDeadlineSeconds.
kubectl rollout: status, history, undo, pause, resume, restart.

Fast

k set image deploy/web nginx=nginx:1.27                  # CONTAINER=IMAGE
k rollout status deploy/web
k rollout history deploy/web                             # --revision=3 shows that revision's template
k rollout undo deploy/web                                # --to-revision=2
k rollout restart deploy/web                             # same spec, new Pods
k annotate deploy/web kubernetes.io/change-cause='pick 1.27'
k patch deploy web -p '{"spec":{"strategy":{"rollingUpdate":{"maxSurge":1,"maxUnavailable":0}}}}'

Traps

--record is deprecated: write the kubernetes.io/change-cause annotation yourself.
An undo makes a new revision out of the old one, so the active revision number is not the one you rolled back to.
A rollout stuck on a bad image does not fail by itself - rollout status just waits, and the old Pods keep serving.
maxSurge and maxUnavailable cannot both be 0.

Docs

https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

Tasks

Q4 Roll forward, then back
Q19 Rolling update without losing capacity
Q42 Back to the last good revision (Simulator Set A (killer.sh-style))
Q44 From a single Pod to a hardened Deployment (Simulator Set A (killer.sh-style))

2.3 Use the Helm package manager to deploy existing packages

./exam study 2.3 (or helm)

Know

A chart is the package, a release is one installation of it in a Namespace, and every install, upgrade or rollback adds a revision.
Values: the chart's defaults (helm show values), overridden with -f file.yaml and --set key=value; helm get values shows what a release was given.
Life cycle: repo add/update, search, install, upgrade, rollback, uninstall, list, history, status.

Fast

helm repo add NAME URL && helm repo update;  helm search repo nginx --versions
helm show values CHART > values.yaml
helm install REL CHART -n NS --create-namespace -f values.yaml --set replicaCount=2    # --version X
helm upgrade REL CHART -n NS --reuse-values --set replicaCount=4
helm list -n NS               # -A for every Namespace;  --failed, --pending filter by status
helm history REL -n NS;  helm rollback REL 1 -n NS;  helm uninstall REL -n NS
helm get values REL -n NS     # --all adds the defaults;   helm get manifest REL -n NS

Traps

Releases live in a Namespace: without -n Helm looks in default and finds nothing.
An upgrade without --reuse-values (or the same -f/--set again) puts every value back to the chart's default.
A rollback is a new revision, not a step back in the numbering.
Helm 3's helm list leaves out pending releases unless you add -a; Helm 4 (on this machine) lists every status and has no -a. --pending and --failed work in both.

Docs

Tasks

Q6 Helm release lifecycle
Q21 Helm: values file and an upgrade that keeps values
Q43 Helm housekeeping (Simulator Set A (killer.sh-style))

2.4 Kustomize

./exam study 2.4 (or kustomize)

Know

A kustomization.yaml lists resources (files or other kustomizations) and transforms them: namespace, namePrefix, nameSuffix, labels, images, replicas, patches.
Generators build ConfigMaps and Secrets from files, env files or literals, add a content hash to the name and rewrite every reference to it.
Base and overlays: an overlay lists ../../base under resources and changes only what differs.
kubectl kustomize DIR prints the result; kubectl apply -k DIR applies it.

Fast

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources: [../../base]                  # or files: [deployment.yaml, service.yaml]
namespace: prod
namePrefix: prod-
labels: [{pairs: {env: prod}, includeSelectors: false}]
images: [{name: nginx, newTag: "1.27"}]
replicas: [{name: web, count: 3}]
patches: [{path: patch.yaml}]            # a partial Deployment with the same name
configMapGenerator: [{name: settings, envs: [settings.env]}]
secretGenerator: [{name: token, literals: [token=abc]}]
generatorOptions: {disableNameSuffixHash: true}
k kustomize DIR | less;  k apply -k DIR;  k diff -k DIR

Traps

Always read the render before you apply it.
images, replicas and patches name things as the base does, before any prefix or suffix.
Refer to a generated ConfigMap by its plain name - Kustomize appends the hash everywhere it is used.
namespace: does not create the Namespace.

Docs

https://kubernetes.io/docs/tasks/manage-kubernetes-objects/kustomization/

Tasks

Q20 Kustomize overlay
Q61 A kustomization that does not build
Q45 Kustomize: a patch and a generated ConfigMap (Simulator Set A (killer.sh-style))

Application Observability and Maintenance (15%)

3.1 Understand API deprecations

./exam study 3.1 (or deprecations)

Know

Every object is a kind in an API group at a version (apps/v1 Deployment). Versions are deprecated, keep being served for some releases, then are removed.
What this cluster serves: kubectl api-resources (the APIVERSION column), kubectl api-versions, kubectl explain KIND.
A removed version fails with no matches for kind "X" in version "g/v"; a deprecated one still works and prints Warning: ... is deprecated.
Migrating is the new apiVersion plus whatever changed shape: an Ingress backend becomes service: {name, port: {number}} with a required pathType, and an apps/v1 Deployment needs spec.selector.

Fast

k api-resources | grep -i -E 'cronjob|ingress'        # NAME  SHORTNAMES  APIVERSION  NAMESPACED  KIND
k api-versions | grep batch
k explain hpa | head -4                               # GROUP, KIND, VERSION
k apply -f old.yaml --dry-run=server                  # the error or warning, without changing anything
# removed, and what replaced them:
#   extensions/v1beta1, networking.k8s.io/v1beta1 Ingress       -> networking.k8s.io/v1   (1.22)
#   extensions/v1beta1, apps/v1beta1, apps/v1beta2 Deployment   -> apps/v1                (1.16)
#   batch/v1beta1 CronJob                                       -> batch/v1               (1.25)
#   policy/v1beta1 PodDisruptionBudget                          -> policy/v1              (1.25)
#   autoscaling/v2beta1, v2beta2 HorizontalPodAutoscaler        -> autoscaling/v2         (1.25, 1.26)

Traps

The kubectl convert plugin is usually not installed - know the Ingress and Deployment rewrites by hand.
kubectl get shows an object in the API's preferred version whatever version it was written with.
A warning is not an error: the object was created. Read stderr.

Docs

Tasks

Q22 Manifests written for removed APIs
Q58 Removed, and deprecated but still served

3.2 Implement probes and health checks

./exam study 3.2 (or probes)

Know

Liveness: failing restarts the container. Readiness: failing takes the Pod out of Service endpoints, no restart. Startup: holds the other two off until it has passed once.
Handlers: httpGet (path, port), tcpSocket (port), exec (command), grpc (port).
Timing: initialDelaySeconds (0), periodSeconds (10), timeoutSeconds (1), failureThreshold (3), successThreshold (1). A startup probe allows failureThreshold x periodSeconds to come up.

Fast

containers:
  - name: app
    startupProbe:   {httpGet: {path: /, port: 80}, periodSeconds: 5, failureThreshold: 12}     # 60 s to start
    readinessProbe: {httpGet: {path: /ready, port: 8080}, periodSeconds: 5, failureThreshold: 1}
    livenessProbe:  {tcpSocket: {port: 80}, initialDelaySeconds: 15, periodSeconds: 10}
    # exec: readinessProbe: {exec: {command: [cat, /tmp/ready]}, periodSeconds: 5}
k describe pod POD | grep -E 'Liveness|Readiness|Startup'
k get events --field-selector reason=Unhealthy
k explain pod.spec.containers.livenessProbe

Traps

No kubectl flag adds a probe: generate the YAML and edit it, or kubectl edit.
Probes belong to a container, not to the Pod spec.
Restarts climbing with Unhealthy and Killing events but nothing wrong in the logs: the liveness probe is wrong or too impatient, not the app.
Running, 0/1 Ready and no restarts: the readiness probe is failing.

Docs

Tasks

Q7 Three kinds of probe
Q62 Health checks that check the wrong thing
Q46 Probes that match the app's warm-up (Simulator Set A (killer.sh-style))

3.3 Use built-in CLI tools to monitor Kubernetes applications

./exam study 3.3 (or monitoring)

Know

kubectl get output: -o wide, yaml, json, name, jsonpath=, custom-columns=; narrowed with -l (labels), --field-selector, -n / -A; ordered with --sort-by.
kubectl top pod|node shows live CPU and memory from metrics-server; --containers splits a Pod up.
kubectl describe for the story of one object, kubectl get events for the Namespace.

Fast

k top pod -A --sort-by=memory;  k top pod --containers;  k top node
k get pods -o wide --sort-by=.spec.nodeName
k get pods -o custom-columns=POD:.metadata.name,NODE:.spec.nodeName,IMAGE:.spec.containers[0].image
k get pod POD -o jsonpath='{.status.phase}'
k get pods -l tier=web --field-selector=status.phase!=Running -o name
k get pods -A --sort-by='.status.containerStatuses[0].restartCount'
k get events --sort-by=.lastTimestamp;  k events --types=Warning --for pod/POD

Traps

kubectl get --sort-by sorts ascending (the largest is last); kubectl top --sort-by sorts descending (the largest is first).
kubectl top shows usage, not requests or limits, and needs about a minute after a Pod starts.
Quote jsonpath for the shell: '{.items[*].metadata.name}'.

Docs

Tasks

Q23 Find the heaviest Pods with kubectl top
Q63 An inventory with kubectl alone
Q48 Restart and event forensics (Simulator Set A (killer.sh-style))
Q38 A Pod and a status one-liner (Simulator Set A (killer.sh-style))

3.4 Utilize container logs

./exam study 3.4 (or logs)

Know

kubectl logs shows what a container wrote to stdout and stderr. The kubelet keeps it on the node, and it goes when the Pod is deleted.
Pick the container with -c (init containers too), or take --all-containers; --previous is the run before the last restart.
Narrow with --tail=N, --since=5m, --timestamps; follow with -f; by label with -l.

Fast

k logs POD -c CONTAINER                       # --all-containers --prefix
k logs POD --previous                         # the crashed run
k logs POD --tail=20 --since=10m --timestamps
k logs -l app=web --prefix --tail=5           # every Pod with the label
k logs deploy/web;  k logs job/render         # one Pod of it
k logs POD | grep ERROR > errors.log

Traps

With -l, only the last 10 lines of each Pod are shown unless you set --tail (--tail=-1 for everything).
kubectl logs deploy/x reads one Pod, not all replicas.
--previous fails when the container has never restarted.

Docs

Tasks

Q24 Logs of a container that keeps crashing
Q64 One replica is logging errors
Q49 RBAC, proven by the app's own log (Simulator Set A (killer.sh-style))
Q54 Expose a Pod and prove it from inside (Simulator Set A (killer.sh-style))
Q39 A suspended CronJob and a manual run (Simulator Set A (killer.sh-style))

3.5 Debugging in Kubernetes

./exam study 3.5 (or debugging)

Know

Always the same order: get (status), describe (Events at the bottom), logs (--previous), then exec or debug.
Pending: nothing can schedule it (resources, taints, nodeSelector, an unbound claim). ImagePullBackOff / ErrImagePull: wrong image or tag. CreateContainerConfigError: a ConfigMap, Secret or key it references is missing.
CrashLoopBackOff: the process exits - read the previous log and lastState.terminated (reason, exitCode). OOMKilled (137): the memory limit is too low.
A Deployment with no Pods at all: describe its ReplicaSet - a quota, a LimitRange or Pod Security admission is rejecting them.

Fast

k get pods -o wide;  k describe pod POD | tail -20
k get pod POD -o jsonpath='{.status.containerStatuses[0].state.waiting.reason}'
k get pod POD -o jsonpath='{.status.containerStatuses[0].lastState.terminated.reason}'    # .exitCode
k logs POD --previous;  k exec -it POD -- sh
k debug -it POD --image=busybox:1.36 --target=CONTAINER     # ephemeral container, sees its processes
k run tmp --rm -it --restart=Never --image=busybox:1.36 -- wget -qO- -T3 http://SVC:PORT
k describe rs -l app=web --show-events | tail;  k get events --sort-by=.lastTimestamp
k get pod POD -o yaml > pod.yaml && vi pod.yaml && k replace --force -f pod.yaml

Traps

Most of a running Pod is immutable (the image is not): fix a bare Pod with replace --force, fix a Deployment's Pods in the Deployment.
Fix what the task names and nothing else - graders check that the ConfigMap, Service or Namespace you were told to leave is unchanged.
After fixing a Deployment wait for the rollout; old Pods linger in Terminating.
kubectl describe with a selector that matches several objects leaves their Events out - add --show-events, or describe one by name.

Docs

Tasks

Q8 Diagnose and fix a broken Pod
Q25 Two faults behind a stuck Deployment
Q26 OOMKilled
Q36 A Service that routes nowhere
Q47 Debugging a container with no shell (Simulator Set A (killer.sh-style))
Q48 Restart and event forensics (Simulator Set A (killer.sh-style))

Application Environment, Configuration and Security (25%)

4.1 Discover and use resources that extend Kubernetes (CRD, Operators)

./exam study 4.1 (or crds)

Know

A CustomResourceDefinition adds a kind to the API; its objects (custom resources) work with every kubectl verb. An operator is a CRD plus a controller acting on those objects.
Discover: k get crd, k api-resources --api-group=GROUP (kind, short names, namespaced or not), k explain KIND.spec.
The CRD's schema validates custom resources: required fields, enum values, minimum and maximum. The controller reports back in .status.

Fast

k get crd | grep -i backup                           # the CRD's name is PLURAL.GROUP
k api-resources --api-group=data.example.com
k explain backup.spec                                # --recursive for the whole tree
k get backups -A;  k get bkp NAME -o yaml;  k describe backup NAME
k get crd backups.data.example.com -o yaml | less    # served versions, schema, enum, maximum
k apply -f cr.yaml --dry-run=server                  # every validation error, nothing created

Traps

A custom resource's apiVersion is the CRD's GROUP/VERSION, never apiextensions.k8s.io/v1.
Field names come from the CRD's schema - check with kubectl explain instead of guessing.
Deleting a CRD deletes every object of that kind.

Docs

Tasks

Q27 Discover and use a custom resource
Q59 A custom resource the API server rejects
Q58 Removed, and deprecated but still served

4.2 Understand authentication, authorization and admission control

./exam study 4.2 (or access)

Know

Every request passes authentication (who is it: a user certificate or token, a ServiceAccount token), authorization (may they: RBAC), then admission control (change or reject it: LimitRanger, ResourceQuota, PodSecurity).
RBAC: a Role or ClusterRole lists verbs on resources (and subresources such as pods/log, deployments/scale); a RoleBinding or ClusterRoleBinding grants it to users, groups or ServiceAccounts.
Pod Security admission: Namespace labels pod-security.kubernetes.io/enforce|warn|audit = privileged | baseline | restricted.
Forbidden: User ... cannot list is authorization. violates PodSecurity, exceeded quota and maximum memory usage are admission.

Fast

k create role ci --verb=get,list,watch --resource=pods,pods/log -n NS
k create role ci --verb=get,update,patch --resource=deployments.apps,deployments.apps/scale -n NS
k create rolebinding ci --role=ci --serviceaccount=NS:SA -n NS        # --user=jane  --clusterrole=view
k auth can-i list pods -n NS --as=system:serviceaccount:NS:SA
k auth can-i --list -n NS --as=system:serviceaccount:NS:SA
k get ns NS --show-labels
# what `restricted` wants from every container:
securityContext: {allowPrivilegeEscalation: false, runAsNonRoot: true, capabilities: {drop: [ALL]},
                  seccompProfile: {type: RuntimeDefault}}

Traps

The same ServiceAccount is --serviceaccount=NS:NAME in a binding and system:serviceaccount:NS:NAME after --as.
can-i create pods/exec asks about a Pod named exec; use can-i create pods --subresource=exec.
Admission rejects Pods, not Deployments: the Deployment exists and shows 0 Pods, and the reason is in its ReplicaSet's events.

Docs

Tasks

Q28 RBAC for a CI ServiceAccount
Q29 Pod Security admission blocks a Deployment
Q49 RBAC, proven by the app's own log (Simulator Set A (killer.sh-style))
Q53 Pods rejected by the Namespace's limits (Simulator Set A (killer.sh-style))

4.3 Understand requests, limits, quotas

./exam study 4.3 (or quotas)

Know

Requests are what the scheduler reserves on a node. Limits are the ceiling: CPU above it is throttled, memory above it gets the container OOMKilled.
A ResourceQuota caps a Namespace's totals (requests.cpu, limits.memory, pods, count/...). Once it covers CPU or memory, every new Pod must state them.
A LimitRange gives containers a default request and limit and enforces a min and max per container, at admission.

Fast

k create quota compute-quota -n NS --hard=requests.cpu=1,requests.memory=1Gi,limits.cpu=2,limits.memory=2Gi,pods=6
k describe quota -n NS                      # Used against Hard
k describe limitrange -n NS
apiVersion: v1
kind: LimitRange
metadata: {name: container-defaults}
spec:
  limits:
    - type: Container
      defaultRequest: {cpu: 100m, memory: 128Mi}     # the request a container gets
      default: {cpu: 250m, memory: 256Mi}            # the LIMIT a container gets
      max: {cpu: 500m, memory: 512Mi}

Traps

default is the default limit and defaultRequest the default request - they are easy to swap.
Quotas and LimitRanges only act on Pods created afterwards.
The rejection is not on the Deployment: k describe rs shows exceeded quota or maximum memory usage per Container.

Docs

Tasks

Q30 Quota with LimitRange defaults
Q26 OOMKilled
Q53 Pods rejected by the Namespace's limits (Simulator Set A (killer.sh-style))

4.4 Understand ConfigMaps

./exam study 4.4 (or configmaps)

Know

Create from literals, files, directories or env files. Each key becomes an environment variable (configMapKeyRef, envFrom) or a file (a configMap volume; items picks keys).
Mounted files follow a changed ConfigMap after a short delay. Environment variables and subPath mounts never do - restart the Pods.
A Pod that references a missing ConfigMap or key waits in CreateContainerConfigError unless the reference is optional: true.

Fast

k create cm app --from-literal=TIER=backend --from-file=app.properties      # --from-file=KEY=path  --from-env-file=x.env
env:
  - {name: APP_TIER, valueFrom: {configMapKeyRef: {name: app, key: TIER}}}
envFrom: [{configMapRef: {name: app}}]
volumes: [{name: cfg, configMap: {name: app, items: [{key: app.properties, path: app.properties}]}}]
volumeMounts: [{name: cfg, mountPath: /etc/app}]         # one file into a full directory: add subPath: app.properties
k set env deploy/web --from=configmap/app;  k exec POD -- env | grep TIER
k rollout restart deploy/web                              # pick up a change

Traps

--from-file makes one key named after the file; --from-env-file makes one key per KEY=VALUE line.
A volume mounted on a directory hides what the image had there.
immutable: true cannot be edited or undone - delete the ConfigMap and create it again.

Docs

Tasks

Q32 ConfigMap as an env var and as a file
Q10 Projected volume: config, secret and token
Q25 Two faults behind a stuck Deployment
Q51 A ConfigMap-driven nginx that needs a restart (Simulator Set A (killer.sh-style))
Q45 Kustomize: a patch and a generated ConfigMap (Simulator Set A (killer.sh-style))

4.5 Define resource requirements

./exam study 4.5 (or resources)

Know

Per container: resources.requests and resources.limits for cpu (cores or millicores: 250m) and memory (Mi, Gi).
QoS class: Guaranteed (every container has requests equal to limits for both CPU and memory), Burstable (some are set), BestEffort (none). BestEffort is evicted first.
A container with a limit but no request gets a request equal to the limit.

Fast

k set resources deploy/web -c app --requests=cpu=250m,memory=128Mi --limits=cpu=250m,memory=128Mi
resources:
  requests: {cpu: 100m, memory: 64Mi}
  limits:   {cpu: 250m, memory: 128Mi}
k get pod POD -o jsonpath='{.status.qosClass}'
k describe node NODE | grep -A8 'Allocated resources'

Traps

kubectl run has no --requests or --limits any more: generate the YAML, or use kubectl set resources on a workload.
Guaranteed needs every container of the Pod, sidecars included.
Memory is Mi, not m: 128m is a fraction of a byte.
A request no node can fit leaves the Pod Pending with Insufficient cpu or Insufficient memory.

Docs

Tasks

Q31 Resource requirements for Guaranteed QoS
Q26 OOMKilled
Q15 DaemonSet on every node
Q53 Pods rejected by the Namespace's limits (Simulator Set A (killer.sh-style))

4.6 Create & consume Secrets

./exam study 4.6 (or secrets)

Know

A Secret's data is base64 - an encoding, not encryption. stringData takes plain text when you write one.
Types: Opaque (generic), kubernetes.io/tls, kubernetes.io/dockerconfigjson, kubernetes.io/service-account-token.
Consumed like a ConfigMap: secretKeyRef, envFrom secretRef, or a secret volume (secretName, defaultMode, items).

Fast

k create secret generic api --from-literal=username=svc --from-literal=password='S3cr3t!'
k create secret tls web-tls --cert=tls.crt --key=tls.key
k create secret docker-registry regcred --docker-server=REG --docker-username=U --docker-password=P
k get secret api -o jsonpath='{.data.password}' | base64 -d
env: [{name: API_USER, valueFrom: {secretKeyRef: {name: api, key: username}}}]
volumes: [{name: creds, secret: {secretName: api, defaultMode: 0400}}]
volumeMounts: [{name: creds, mountPath: /etc/creds, readOnly: true}]

Traps

A secret volume names it with secretName; a configMap volume uses name.
Encoding by hand: echo -n value | base64, or the newline becomes part of the secret.
defaultMode is octal in YAML (0400) and shows as decimal in JSON (256).

Docs

Tasks

Q33 Secrets: decode one, consume another
Q10 Projected volume: config, secret and token
Q37 Ingress with two paths and TLS
Q50 An immutable Secret, one file into a busy directory (Simulator Set A (killer.sh-style))

4.7 Understand ServiceAccounts

./exam study 4.7 (or serviceaccounts)

Know

Every Pod runs as a ServiceAccount (default if you name none); its short-lived token is mounted at /var/run/secrets/kubernetes.io/serviceaccount.
Choose it with spec.serviceAccountName. Stop the mount with automountServiceAccountToken: false on the ServiceAccount or on the Pod (the Pod wins).
Tokens: kubectl create token for a short-lived one; a Secret of type kubernetes.io/service-account-token annotated with the account's name for a long-lived one.
A ServiceAccount can do nothing until RBAC binds a Role to it.

Fast

k create sa ci -n NS
k set serviceaccount deploy/web ci -n NS             # = spec.template.spec.serviceAccountName
k patch sa ci -n NS -p '{"automountServiceAccountToken": false}'
k create token ci -n NS --duration=1h
k auth can-i list pods -n NS --as=system:serviceaccount:NS:ci
apiVersion: v1
kind: Secret
metadata: {name: ci-token, annotations: {kubernetes.io/service-account.name: ci}}
type: kubernetes.io/service-account-token

Traps

No token Secret is made for a new ServiceAccount (since 1.24) - create it yourself when a task wants one.
serviceAccountName cannot be changed on a running Pod; on a Deployment it starts a rollout.
A Pod naming a ServiceAccount that does not exist is never created - see the ReplicaSet's events.

Docs

Tasks

Q34 ServiceAccount without an automounted token
Q28 RBAC for a CI ServiceAccount
Q10 Projected volume: config, secret and token
Q49 RBAC, proven by the app's own log (Simulator Set A (killer.sh-style))

4.8 Understand Application Security (SecurityContexts, Capabilities, etc.)

./exam study 4.8 (or security)

Know

Pod level (spec.securityContext): runAsUser, runAsGroup, runAsNonRoot, fsGroup, supplementalGroups, seccompProfile - for every container.
Container level adds allowPrivilegeEscalation, privileged, readOnlyRootFilesystem and capabilities, and overrides the Pod level.
Capabilities are written without the CAP_ prefix: NET_BIND_SERVICE, NET_ADMIN, SYS_TIME. Drop ALL, then add back what the app needs.

Fast

spec:
  securityContext: {runAsUser: 1000, runAsGroup: 1000, runAsNonRoot: true, fsGroup: 2000}
  containers:
    - name: app
      securityContext:
        allowPrivilegeEscalation: false
        readOnlyRootFilesystem: true
        capabilities: {drop: [ALL], add: [NET_BIND_SERVICE]}
k exec POD -- id
k explain pod.spec.securityContext;  k explain pod.spec.containers.securityContext

Traps

capabilities exist only on a container, fsGroup only on the Pod.
runAsNonRoot with an image that runs as root and no runAsUser: CreateContainerConfigError.
readOnlyRootFilesystem breaks an app that writes to /tmp or /var/cache - mount an emptyDir there.

Docs

https://kubernetes.io/docs/tasks/configure-pod-container/security-context/

Tasks

Q9 SecurityContext and capabilities
Q29 Pod Security admission blocks a Deployment
Q44 From a single Pod to a hardened Deployment (Simulator Set A (killer.sh-style))
Q52 Two users, one volume: fsGroup (Simulator Set A (killer.sh-style))

Services and Networking (20%)

5.1 Demonstrate basic understanding of NetworkPolicies

./exam study 5.1 (or netpol)

Know

Pods accept and send everything until a NetworkPolicy selects them. From then on, for the policyTypes it lists, only what some policy allows gets through.
Policies only allow, and they add up: there is no deny rule and no ordering.
Peers: podSelector (same Namespace), namespaceSelector, ipBlock. Two selectors in one list item mean AND; two list items mean OR.
Default deny: podSelector: {} with a policyType and no rules. Locking down egress also needs DNS allowed (UDP and TCP 53).

Fast

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata: {name: db-allow, namespace: NS}
spec:
  podSelector: {matchLabels: {app: db}}
  policyTypes: [Ingress]
  ingress:
    - from:
        - podSelector: {matchLabels: {app: api}}                        # OR
        - namespaceSelector: {matchLabels: {purpose: monitoring}}
      ports: [{protocol: TCP, port: 5432}]
# egress that keeps DNS:   egress: [{ports: [{protocol: UDP, port: 53}, {protocol: TCP, port: 53}]}, ...]
k describe netpol db-allow -n NS
k exec CLIENT -- wget -qO- -T2 http://db:5432           # test it with real traffic

Traps

There is no kubectl create networkpolicy - copy the skeleton from the docs.
- podSelector: ... followed by namespaceSelector: in the same item is AND; a second - namespaceSelector: is OR.
A missing or empty ingress denies everything; ingress: [{}] allows everything.
The policy lives in the Namespace of the Pods it selects, and a Namespace is matched by its labels (kubernetes.io/metadata.name=NAME always exists).

Docs

https://kubernetes.io/docs/concepts/services-networking/network-policies/

Tasks

Q12 Restrict a namespace with NetworkPolicy
Q35 Egress lockdown that keeps DNS working
Q55 Two sources, one port (Simulator Set A (killer.sh-style))

5.2 Provide and troubleshoot access to applications via services

./exam study 5.2 (or services)

Know

A Service selects Pods by label and forwards port to targetPort (a number, or the name of a container port).
Types: ClusterIP (inside the cluster), NodePort (30000-32767 on every node), LoadBalancer, ExternalName; headless (clusterIP: None) gives each Pod its own DNS record.
DNS names: SVC, SVC.NS, SVC.NS.svc.cluster.local.
Troubleshoot in this order: are there endpoints, does the selector match the Pod labels, are the Pods Ready, is targetPort the port the container listens on.

Fast

k expose deploy web --port=8080 --target-port=80          # --name=web-svc  --type=NodePort
k create svc nodeport web-ext --tcp=80:80 --node-port=30080
k get svc,endpointslices -o wide;  k describe svc web     # Endpoints: <none> = nothing selected
k get pods -l app=web --show-labels
k run tmp --rm -it --restart=Never --image=busybox:1.36 -- wget -qO- -T3 http://web:8080
k port-forward svc/web 8080:80

Traps

kubectl expose copies the workload's selector; kubectl create svc selects app=, which may match nothing.
expose cannot choose the nodePort - use create svc nodeport --node-port or edit the YAML.
A Service without endpoints still resolves in DNS; the connection is what fails.

Docs

Tasks

Q11 Expose a Deployment two ways
Q36 A Service that routes nowhere
Q54 Expose a Pod and prove it from inside (Simulator Set A (killer.sh-style))
Q56 Stable DNS names for a StatefulSet (Simulator Set A (killer.sh-style))

5.3 Use Ingress rules to expose applications

./exam study 5.3 (or ingress)

Know

An Ingress routes HTTP(S) by host and path to Services of its own Namespace; an ingress controller, chosen with ingressClassName, does the work.
Each path has a pathType (Prefix, Exact or ImplementationSpecific) and a backend: service.name plus service.port.number or .name.
TLS: spec.tls lists hosts and the kubernetes.io/tls Secret that holds their certificate.

Fast

k create ingress shop --class=nginx \
  --rule="shop.example.com/api*=api:8080,tls=shop-tls" --rule="shop.example.com/*=web:80,tls=shop-tls"
k create secret tls shop-tls --cert=tls.crt --key=tls.key
k get ingress,ingressclass;  k describe ingress shop     # a missing backend shows as <error: services "x" not found>
k explain ingress.spec.rules.http.paths

Traps

In --rule a trailing * means pathType Prefix; without it the path is Exact.
The backend port is the Service's port, not the container's.
No ingress controller runs in this simulator, so Ingress tasks are graded on the object - on the exam, curl it.

Docs

https://kubernetes.io/docs/concepts/services-networking/ingress/

Tasks

Q37 Ingress with two paths and TLS
Q11 Expose a Deployment two ways
Q57 An Ingress pointing at the wrong backends (Simulator Set A (killer.sh-style))

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CKAD study guide

Application Design and Build (20%)

1.1 Define, build and modify container images

1.2 Choose and use the right workload resource (Deployment, DaemonSet, CronJob, etc.)

1.3 Understand multi-container Pod design patterns (e.g. sidecar, init and others)

1.4 Utilize persistent and ephemeral volumes

Application Deployment (20%)

2.1 Use Kubernetes primitives to implement common deployment strategies (e.g. blue/green or canary)

2.2 Understand Deployments and how to perform rolling updates

2.3 Use the Helm package manager to deploy existing packages

2.4 Kustomize

Application Observability and Maintenance (15%)

3.1 Understand API deprecations

3.2 Implement probes and health checks

3.3 Use built-in CLI tools to monitor Kubernetes applications

3.4 Utilize container logs

3.5 Debugging in Kubernetes

Application Environment, Configuration and Security (25%)

4.1 Discover and use resources that extend Kubernetes (CRD, Operators)

4.2 Understand authentication, authorization and admission control

4.3 Understand requests, limits, quotas

4.4 Understand ConfigMaps

4.5 Define resource requirements

4.6 Create & consume Secrets

4.7 Understand ServiceAccounts

4.8 Understand Application Security (SecurityContexts, Capabilities, etc.)

Services and Networking (20%)

5.1 Demonstrate basic understanding of NetworkPolicies

5.2 Provide and troubleshoot access to applications via services

5.3 Use Ingress rules to expose applications

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