Pass the Linux Foundation Kubernetes Security Specialist CKS Questions and answers with CertsForce

se kubectl to create a CSR and approve it.

Get the list of CSRs:

kubectl get csr

Approve the CSR:

kubectl certificate approve myuser

Retrieve the certificate from the CSR:

kubectl get csr/myuser -o yaml

here are the role and role-binding to give john permission to create NEW_CRD resource:

kubectl apply -f roleBindingJohn.yaml --as=john

rolebinding.rbac.authorization.k8s.io/john_external-rosource-rb created

kind: RoleBinding

apiVersion: rbac.authorization.k8s.io/v1

metadata:

name: john_crd

namespace: development-john

subjects:

- kind: User

name: john

apiGroup: rbac.authorization.k8s.io

roleRef:

kind: ClusterRole

name: crd-creation

kind: ClusterRole

apiVersion: rbac.authorization.k8s.io/v1

metadata:

name: crd-creation

rules:

- apiGroups: ["kubernetes-client.io/v1"]

resources: ["NEW_CRD"]

verbs: ["create, list, get"]

$ vim /etc/kubernetes/log-policy/audit-policy.yaml

- level: RequestResponse

userGroups: ["system:nodes"]

- level: Request

resources:

- group: "" # core API group

resources: ["persistentvolumes"]

namespaces: ["frontend"]

- level: Metadata

resources:

- group: ""

resources: ["configmaps", "secrets"]

- level: Metadata

$ vim /etc/kubernetes/manifests/kube-apiserver.yaml

Add these

- --audit-policy-file=/etc/kubernetes/log-policy/audit-policy.yaml

- --audit-log-path=/var/log/kubernetes/logs.txt

- --audit-log-maxage=5

- --audit-log-maxbackup=10

Explanation[desk@cli] $ ssh master1

[master1@cli] $ vim /etc/kubernetes/log-policy/audit-policy.yaml

apiVersion: audit.k8s.io/v1 # This is required.

kind: Policy

# Don't generate audit events for all requests in RequestReceived stage.

omitStages:

- "RequestReceived"

rules:

# Don't log watch requests by the "system:kube-proxy" on endpoints or services

- level: None

users: ["system:kube-proxy"]

verbs: ["watch"]

resources:

- group: "" # core API group

resources: ["endpoints", "services"]

# Don't log authenticated requests to certain non-resource URL paths.

- level: None

userGroups: ["system:authenticated"]

nonResourceURLs:

- "/api*" # Wildcard matching.

- "/version"

# Add your changes below

- level: RequestResponse

userGroups: ["system:nodes"] # Block for nodes

- level: Request

resources:

- group: "" # core API group

resources: ["persistentvolumes"] # Block for persistentvolumes

namespaces: ["frontend"] # Block for persistentvolumes of frontend ns

- level: Metadata

resources:

- group: "" # core API group

resources: ["configmaps", "secrets"] # Block for configmaps & secrets

- level: Metadata # Block for everything else

[master1@cli] $ vim /etc/kubernetes/manifests/kube-apiserver.yaml

apiVersion: v1

kind: Pod

metadata:

annotations:

kubeadm.kubernetes.io/kube-apiserver.advertise-address.endpoint: 10.0.0.5:6443

labels:

component: kube-apiserver

tier: control-plane

name: kube-apiserver

namespace: kube-system

spec:

containers:

- command:

- kube-apiserver

- --advertise-address=10.0.0.5

- --allow-privileged=true

- --authorization-mode=Node,RBAC

- --audit-policy-file=/etc/kubernetes/log-policy/audit-policy.yaml #Add this

- --audit-log-path=/var/log/kubernetes/logs.txt #Add this

- --audit-log-maxage=5 #Add this

- --audit-log-maxbackup=10 #Add this

output truncated

Note: log volume & policy volume is already mounted in vim /etc/kubernetes/manifests/kube-apiserver.yaml so no need to mount it.

Below is the CKS exam-ready, step-by-step solution for QUESTION 15.

Follow exactly in this order. No extra changes.

QUESTION 15 — Istio mTLS (EXAM MODE)

1) Connect to the correct host

ssh cks000041

sudo -i

export KUBECONFIG=/etc/kubernetes/admin.conf

2) Ensure sidecar injection is enabled for the mtls namespace

2.1 Check current namespace labels

kubectl get ns mtls --show-labels

2.2 Enable automatic Istio sidecar injection

kubectl label namespace mtls istio-injection=enabled --overwrite

Verify:

kubectl get ns mtls --show-labels | grep istio-injection

Expected:

istio-injection=enabled

3) Ensure ALL Pods get the istio-proxy sidecar

Existing Pods will not get sidecars automatically.

You must restart workloads in the namespace.

3.1 Restart all Deployments in mtls

kubectl -n mtls rollout restart deployment

3.2 Verify Pods now have 2 containers (app + istio-proxy)

kubectl -n mtls get pods

Then check one Pod:

kubectl -n mtls get pod -o jsonpath='{.spec.containers[*].name}{"\n"}'

Expected output includes:

istio-proxy

4) Configure mutual TLS (mTLS) in STRICT mode

4.1 Create a PeerAuthentication for the mtls namespace

cat <

apiVersion: security.istio.io/v1beta1

kind: PeerAuthentication

metadata:

name: mtls-strict

namespace: mtls

spec:

mtls:

mode: STRICT

EOF

5) Verify mTLS policy is applied

kubectl -n mtls get peerauthentication

kubectl -n mtls describe peerauthentication mtls-strict

Expected:

Mode: STRICT

6) Final verification (exam confidence check)

6.1 Confirm all Pods are Running

kubectl -n mtls get pods

6.2 Confirm sidecar injection everywhere

kubectl -n mtls get pods -o jsonpath='{range .items[*]}{.metadata.name}{" -> "}{.spec.containers[*].name}{"\n"}{end}'

Each line must include istio-proxy.

1) Connect to the correct host

ssh cks000032

sudo -i

2) Use admin kubeconfig

export KUBECONFIG=/etc/kubernetes/admin.conf

3) Verify prerequisites (quick check)

These should already exist per task.

kubectl -n prod get svc web

kubectl -n prod get secret web-cert

kubectl get pods -n ingress-nginx

(If the ingress controller pods exist, you’re good.)

4) Create the Ingress resource

Create Ingress named web in namespace prod with:

host: web.k8s.local

all paths → Service web

TLS using Secret web-cert

HTTP → HTTPS redirect (NGINX)

cat <

apiVersion: networking.k8s.io/v1

kind: Ingress

metadata:

name: web

namespace: prod

annotations:

nginx.ingress.kubernetes.io/ssl-redirect: "true"

nginx.ingress.kubernetes.io/force-ssl-redirect: "true"

spec:

ingressClassName: nginx

tls:

- hosts:

- web.k8s.local

secretName: web-cert

rules:

- host: web.k8s.local

http:

paths:

- path: /

pathType: Prefix

backend:

service:

name: web

port:

number: 80

EOF

5) Verify Ingress creation

kubectl -n prod get ingress web

kubectl -n prod describe ingress web

Confirm:

Host = web.k8s.local

TLS Secret = web-cert

Backend Service = web

6) Test HTTP → HTTPS redirect

curl -L http://web.k8s.local

Expected:

Redirects to https://web.k8s.local

Returns application response over HTTPS

1) SSH to the right node

ssh cks000002

sudo -i

2) Fix kubelet CIS findings

2.1 Edit kubelet config (MAIN place in kubeadm clusters)

vi /var/lib/kubelet/config.yaml

A) Set anonymous-auth to false

Find (or add) this block exactly:

authentication:

anonymous:

enabled: false

B) Use Webhook authentication (recommended by task)

Ensure this exists under authentication:

webhook:

enabled: true

C) Use Webhook authorization and NOT AlwaysAllow

Find (or add) this block exactly:

authorization:

mode: Webhook

When done, your file should contain something like this (exact structure to aim for):

authentication:

anonymous:

enabled: false

webhook:

enabled: true

x509:

clientCAFile: /etc/kubernetes/pki/ca.crt

authorization:

mode: Webhook

If x509: section isn’t there, it’s usually already present in kubeadm; don’t panic. Only the task-required parts are: anonymous false + webhook enabled + authorization mode Webhook.

2.2 Restart kubelet (required for config.yaml changes)

systemctl daemon-reload

systemctl restart kubelet

systemctl status kubelet --no-pager

Quick confirm (optional but fast):

grep -nE "anonymous|webhook|authorization|mode" /var/lib/kubelet/config.yaml

3) Fix etcd CIS finding: --client-cert-auth=true

3.1 Edit etcd static pod manifest (kubeadm path)

vi /etc/kubernetes/manifests/etcd.yaml

Find the container command: args that look like:

- command:

- etcd

- --something=...

Ensure this line exists exactly in the list:

- --client-cert-auth=true

Also ensure this is present (usually already is, but add if missing):

- --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt

Example snippet (what you want the args area to include):

- command:

- etcd

- --client-cert-auth=true

- --trusted-ca-file=/etc/kubernetes/pki/etcd/ca.crt

3.2 Apply etcd change (auto-restart happens)

Just save the file. Kubelet will restart etcd automatically.

Watch it restart (pick one depending on runtime):

If Docker runtime (your task mentions Docker):

docker ps | grep etcd

If you don’t see it briefly, wait 2–5 seconds and rerun:

docker ps | grep etcd

(Alternative if available)

crictl ps | grep etcd

4) Final quick validation (fast exam check)

Kubelet config check

grep -n "enabled: false" -n /var/lib/kubelet/config.yaml | head

grep -n "webhook" /var/lib/kubelet/config.yaml

grep -n "authorization" /var/lib/kubelet/config.yaml

etcd arg check

grep -n "client-cert-auth" /etc/kubernetes/manifests/etcd.yaml

master1 $ k get pods -n test --show-labels

NAME READY STATUS RESTARTS AGE LABELS

test-pod 1/1 Running 0 34s role=test,run=test-pod

testing 1/1 Running 0 17d run=testing

$ vim netpol.yaml

apiVersion: networking.k8s.io/v1

kind: NetworkPolicy

metadata:

name: deny-network

namespace: test

spec:

podSelector: {}

policyTypes:

- Ingress

- Egress

master1 $ k apply -f netpol.yaml

Explanationcontrolplane $ k get pods -n test --show-labels

NAME READY STATUS RESTARTS AGE LABELS

test-pod 1/1 Running 0 34s role=test,run=test-pod

testing 1/1 Running 0 17d run=testing

master1 $ vim netpol1.yaml

apiVersion: networking.k8s.io/v1

kind: NetworkPolicy

metadata:

name: deny-network

namespace: test

spec:

podSelector: {}

policyTypes:

- Ingress

- Egress

master1 $ k apply -f netpol1.yaml

1) Connect to correct host

ssh cks000033

sudo -i

export KUBECONFIG=/etc/kubernetes/admin.conf

2) Patch the ServiceAccount to disable automounting

Task: turn off automounting of API credentials for stats-monitor-sa in monitoring.

kubectl -n monitoring patch sa stats-monitor-sa -p '{"automountServiceAccountToken": false}'

Verify:

kubectl -n monitoring get sa stats-monitor-sa -o yaml | grep -i automount

3) Edit the Deployment manifest file

Task says to modify the manifest at:

/home/candidate/stats-monitor/deployment.yaml

vi /home/candidate/stats-monitor/deployment.yaml

4) In the Deployment, ensure it uses the ServiceAccount AND inject token via Projected Volume

4.1 Make sure Deployment uses the SA

Under:

spec: -> template: -> spec:

ensure:

serviceAccountName: stats-monitor-sa

(If it already exists, leave it; don’t add extra changes beyond requirements.)

4.2 Add a projected volume named token

Under:

spec: -> template: -> spec: -> volumes:

add (or modify existing volume if present) so it is exactly:

- name: token

projected:

sources:

- serviceAccountToken:

path: token

This creates the file token inside the mounted directory, so the final path becomes:

/var/run/secrets/kubernetes.io/serviceaccount/token

4.3 Mount the projected volume read-only at the required location

Under the target container:

spec: -> template: -> spec: -> containers: -> (your container) -> volumeMounts:

Add:

- name: token

mountPath: /var/run/secrets/kubernetes.io/serviceaccount

readOnly: true

✅ This satisfies:

Projected volume name: token

Mount path: /var/run/secrets/kubernetes.io/serviceaccount/token (file inside mount)

Mounted read-only

4.4 Important: Don’t break default token mount behavior

Because you disabled SA automounting at the ServiceAccount level, you must explicitly mount the projected token (done above). That’s the whole point of this task.

Save and exit:

wq

5) Apply the updated Deployment

kubectl -n monitoring apply -f /home/candidate/stats-monitor/deployment.yaml

Wait rollout:

kubectl -n monitoring rollout status deployment/stats-monitor

6) Verify the token file exists in the running Pod

Get a pod name:

POD=$(kubectl -n monitoring get pods -l app=stats-monitor -o jsonpath='{.items[0].metadata.name}')

echo $POD

Check the token file path exists:

kubectl -n monitoring exec -it $POD -- ls -l /var/run/secrets/kubernetes.io/serviceaccount/token

Optional: confirm it’s mounted read-only (usually shown by mount options):

kubectl -n monitoring exec -it $POD -- mount | grep /var/run/secrets/kubernetes.io/serviceaccount

✅ What the examiner checks

SA stats-monitor-sa has:

automountServiceAccountToken: false

Deployment stats-monitor mounts a projected volume named token

Token file is at:

/var/run/secrets/kubernetes.io/serviceaccount/token

Mount is readOnly: true

If label selector doesn’t match (-l app=stats-monitor)

Use:

kubectl -n monitoring get pods

Then set:

POD=