See the Explanation below for complete solution
Explanation:
0) Connect to the correct host
ssh cks000023
sudo -i
PART A - Fix ONE prominent Dockerfile security/best-practice issue
1) Open the Dockerfile
vi /home/candidate/subtle-bee/build/Dockerfile
2) Find the "most obvious" security/best-practice problem and modify ONLY THAT ONE instruction Use / search in vi to quickly find candidates:
Candidate 1 (very common): USER root (or no USER but a USER 0)
Search:
/USER
If you see:
USER root
Change that single instruction to:
USER 65535
(or USER nobody if that exact word is already used in the file-but the task explicitly allows UID 65535, so USER 65535 is safest.)
✅ This is one-instruction change and is a top-tier best practice.
Candidate 2 (very common): FROM <image>:latest
Search:
/FROM
If you see something like:
FROM nginx:latest
Change ONLY that line to a pinned tag (example):
FROM nginx:1.25.5
(Any non-latest pinned version is the point. Don't add a digest line; just modify the existing FROM line.) Candidate 3: ADD http://... (remote URL download) Search:
/ADD
If you see remote URL usage like:
ADD https://example.com/app.tar.gz /app/
Change that single instruction to COPY only if it's copying local files.
If it's a remote URL, the more "correct" fix would normally be using curl with verification, but that would require adding instructions (not allowed).
So in this exam constraint, do NOT pick this unless it's actually a local add like:
ADD . /app
Then change just the word:
COPY . /app
3) Save and exit
:wq
Don't run docker build (task forbids building).
PART B - Fix ONE prominent security/best-practice issue in the Deployment manifest
4) Open the manifest
vi /home/candidate/subtle-bee/deployment.yaml
5) Change ONLY ONE existing field that is a clear security issue
Use / search in vi for the usual "bad fields":
Option 1 (most common): running as root
Search:
/runAsUser
If you see:
runAsUser: 0
Change that one existing field value to:
runAsUser: 65535
✅ This is a single-field change and matches the prompt hint.
Option 2: privileged container
Search:
/privileged
If you see:
privileged: true
Change only that value to:
privileged: false
Option 3: allow privilege escalation
Search:
/allowPrivilegeEscalation
If you see:
allowPrivilegeEscalation: true
Change only that value to:
allowPrivilegeEscalation: false
Option 4: writable root filesystem
Search:
/readOnlyRootFilesystem
If you see:
readOnlyRootFilesystem: false
Change only that value to:
readOnlyRootFilesystem: true
Option 5: image uses :latest
Search:
/image:
If you see:
image: something:latest
Change only that value to a pinned tag, e.g.:
image: something:1.2.3
6) Save and exit
:wq
What to pick (fast decision rule)
If you see run as root in either file, that's usually the highest scoring / most "prominent" security issue.
Dockerfile: USER root → USER 65535
Deployment: runAsUser: 0 → runAsUser: 65535
Those are perfect because you only modify one line/field and it matches the hint.

See the Explanation below for complete solution
Explanation:
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 <pod-name> -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 <<EOF | kubectl apply -f -
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.

See the Explanation belowExplanation:
Fix all of the following violations that were found against the API server:- a. Ensure that the RotateKubeletServerCertificate argument is set to true.
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: kubelet
tier: control-plane
name: kubelet
namespace: kube-system
spec:
containers:
- command:
- kube-controller-manager
+ - --feature-gates=RotateKubeletServerCertificate=true
image: gcr.io/google_containers/kubelet-amd64:v1.6.0
livenessProbe:
failureThreshold: 8
httpGet:
host: 127.0.0.1
path: /healthz
port: 6443
scheme: HTTPS
initialDelaySeconds: 15
timeoutSeconds: 15
name: kubelet
resources:
requests:
cpu: 250m
volumeMounts:
- mountPath: /etc/kubernetes/
name: k8s
readOnly: true
- mountPath: /etc/ssl/certs
name: certs
- mountPath: /etc/pki
name: pki
hostNetwork: true
volumes:
- hostPath:
path: /etc/kubernetes
name: k8s
- hostPath:
path: /etc/ssl/certs
name: certs
- hostPath:
path: /etc/pki
name: pki
b. Ensure that the admission control plugin PodSecurityPolicy is set.
audit: "/bin/ps -ef | grep $apiserverbin | grep -v grep"
tests:
test_items:
- flag: "--enable-admission-plugins"
compare:
op: has
value: "PodSecurityPolicy"
set: true
remediation: |
Follow the documentation and create Pod Security Policy objects as per your environment.
Then, edit the API server pod specification file $apiserverconf
on the master node and set the --enable-admission-plugins parameter to a value that includes PodSecurityPolicy :
--enable-admission-plugins=...,PodSecurityPolicy,...
Then restart the API Server.
scored: true
c. Ensure that the --kubelet-certificate-authority argument is set as appropriate.
audit: "/bin/ps -ef | grep $apiserverbin | grep -v grep"
tests:
test_items:
- flag: "--kubelet-certificate-authority"
set: true
remediation: |
Follow the Kubernetes documentation and setup the TLS connection between the apiserver and kubelets. Then, edit the API server pod specification file
$apiserverconf on the master node and set the --kubelet-certificate-authority parameter to the path to the cert file for the certificate authority.
--kubelet-certificate-authority=<ca-string>
scored: true
Fix all of the following violations that were found against the ETCD:-
a. Ensure that the --auto-tls argument is not set to true
Edit the etcd pod specification file $etcdconf on the master
node and either remove the --auto-tls parameter or set it to false.
--auto-tls=false
b. Ensure that the --peer-auto-tls argument is not set to true
Edit the etcd pod specification file $etcdconf on the master
node and either remove the --peer-auto-tls parameter or set it to false.
--peer-auto-tls=false

See the Explanation belowExplanation:

See the Explanation below
Explanation: