CKS Practice Questions

Below is the CKS / CKA exam-style, exact step-by-step solution for Upgrading a kubeadm worker node.

Follow in order, type exact commands, no extra actions.

QUESTION — Upgrade node compute-0 (EXAM MODE)

1) Connect to the correct host (control plane)

ssh cks000034

sudo -i

export KUBECONFIG=/etc/kubernetes/admin.conf

2) Identify the control plane Kubernetes version

This is the target version for compute-0.

kubectl get nodes

Example output:

NAME STATUS ROLES VERSION

control-plane Ready control-plane v1.27.4

compute-0 Ready v1.26.6

???? Note the control-plane version

Example: v1.27.4

3) Drain the compute node (do NOT modify workloads manually)

kubectl drain compute-0 --ignore-daemonsets --delete-emptydir-data

Wait until drain completes successfully.

4) SSH into the compute node

ssh compute-0

sudo -i

5) Check current kubeadm version on compute node

kubeadm version

6) Upgrade kubeadm to match control plane version

Replace 1.27.4 with the exact control-plane version you observed.

apt-get update

apt-get install -y kubeadm=1.27.4-00

Verify:

kubeadm version

7) Run kubeadm upgrade for the node

kubeadm upgrade node

✅ This updates node-specific configs (NO workloads touched).

8) Upgrade kubelet and kubectl to the same version

apt-get install -y kubelet=1.27.4-00 kubectl=1.27.4-00

9) Restart kubelet

systemctl daemon-reload

systemctl restart kubelet

systemctl status kubelet --no-pager

10) Exit the compute node (IMPORTANT)

exit

11) Uncordon the compute node (back on control plane)

kubectl uncordon compute-0

12) Final verification

kubectl get nodes

Expected:

NAME STATUS VERSION

compute-0 Ready v1.27.4

1) Connect to the correct host

ssh cks000026

sudo -i

2) Identify the misbehaving Pod accessing /dev/mem

This task hints Falco is available → use it first (fast + intended).

2.1 Check Falco logs for /dev/mem access

journalctl -u falco | grep dev/mem

If Falco runs as a pod instead of systemd:

kubectl -n falco logs -l app=falco | grep dev/mem

2.2 Identify the Pod name

From the Falco output, you will see something like:

Pod=ollama-xxxxx Namespace=default File=/dev/mem

???? Note the exact Pod name (example: ollama-7c9d6f7b6d-abcde)

3) (If Falco logs are unclear) Confirm using Docker runtime

Because the cluster uses Docker, verify which container is accessing /dev/mem.

3.1 List running containers

docker ps

3.2 Inspect suspicious container

(Find container related to ollama)

docker inspect | grep ollama

You should confirm it maps to the same Pod you saw in Falco.

4) Identify the Deployment managing the misbehaving Pod

4.1 Get Pod details

kubectl get pod -o wide

4.2 Find owning Deployment

kubectl get pod -o jsonpath='{.metadata.ownerReferences[0].name}'

This will output something like:

ollama

???? That is the Deployment name

5) Scale ONLY that Deployment to zero replicas

⚠️ Do not edit, delete, or touch anything else

kubectl scale deployment ollama --replicas=0

6) Verify the Pod is terminated

kubectl get pods | grep ollama

Expected: no running Pods

Also confirm replicas:

kubectl get deployment ollama

Replicas should show:

0/0

Explanation[desk@cli] $vim runtime.yaml

apiVersion: node.k8s.io/v1

kind: RuntimeClass

metadata:

 name: not-trusted

handler: runsc

[desk@cli] $ k apply -f runtime.yaml

[desk@cli] $ k get pods

NAME READY STATUS RESTARTS AGE

nginx-6798fc88e8-chp6r 1/1 Running 0 11m

nginx-6798fc88e8-fs53n 1/1 Running 0 11m

nginx-6798fc88e8-ndved 1/1 Running 0 11m

[desk@cli] $ k get deploy

NAME READY UP-TO-DATE AVAILABLE AGE

nginx 3/3 11 3 5m

[desk@cli] $ k edit deploy nginx

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

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.

$ kubectl get ing -n

NAME HOSTS ADDRESS PORTS AGE

cafe-ingress cafe.com 10.0.2.15 80 25s

$ kubectl describe ing -n

Name: cafe-ingress

Namespace: default

Address: 10.0.2.15

Default backend: default-http-backend:80 (172.17.0.5:8080)

Rules:

Host Path Backends

---- ---- --------

cafe.com

/tea tea-svc:80 ()

/coffee coffee-svc:80 ()

Annotations:

kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"networking.k8s.io/v1","kind":"Ingress","metadata":{"annotations":{},"name":"cafe-ingress","namespace":"default","selfLink":"/apis/networking/v1/namespaces/default/ingresses/cafe-ingress"},"spec":{"rules":[{"host":"cafe.com","http":{"paths":[{"backend":{"serviceName":"tea-svc","servicePort":80},"path":"/tea"},{"backend":{"serviceName":"coffee-svc","servicePort":80},"path":"/coffee"}]}}]},"status":{"loadBalancer":{"ingress":[{"ip":"169.48.142.110"}]}}}

Events:

Type Reason Age From Message

---- ------ ---- ---- -------

Normal CREATE 1m ingress-nginx-controller Ingress default/cafe-ingress

Normal UPDATE 58s ingress-nginx-controller Ingress default/cafe-ingress

$ kubectl get pods -n

NAME READY STATUS RESTARTS AGE

ingress-nginx-controller-67956bf89d-fv58j 1/1 Running 0 1m

$ kubectl logs -n ingress-nginx-controller-67956bf89d-fv58j

-------------------------------------------------------------------------------

NGINX Ingress controller

Release: 0.14.0

Build: git-734361d

Repository: https://github.com/kubernetes/ingress-nginx

-------------------------------------------------------------------------------

root# netstat -ltnup

Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

tcp 0 0 127.0.0.1:17600 0.0.0.0:* LISTEN 1293/dropbox

tcp 0 0 127.0.0.1:17603 0.0.0.0:* LISTEN 1293/dropbox

tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 575/sshd

tcp 0 0 127.0.0.1:9393 0.0.0.0:* LISTEN 900/perl

tcp 0 0 :::80 :::* LISTEN 9583/docker-proxy

tcp 0 0 :::443 :::* LISTEN 9571/docker-proxy

udp 0 0 0.0.0.0:68 0.0.0.0:* 8822/dhcpcd

root# netstat -ltnup | grep ':22'

tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 575/sshd

The ss command is the replacement of the netstat command.

Now let’s see how to use the ss command to see which process is listening on port 22:

root# ss -ltnup 'sport = :22'

Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port

tcp LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:("sshd",pid=575,fd=3))