CKAD-exercises 오답노트

hyereen·2025년 2월 2일

Kubernetes

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출처: https://github.com/dgkanatsios/CKAD-exercises

a. Core Concepts

Create the YAML for a new ResourceQuota called 'myrq' with hard limits of 1 CPU, 1G memory and 2 pods without creating it

정답

kubectl create quota myrq --hard=cpu=1,memory=1G,pods=2 --dry-run=client -o yaml

참고

https://kubernetes.io/docs/reference/kubectl/generated/kubectl_create/kubectl_create_quota/#examples

Create a pod with image nginx called nginx and expose traffic on port 80

정답

kubectl run nginx --image=nginx --restart=Never --port=80

Change pod's image to nginx:1.24.0. Observe that the container will be restarted as soon as the image gets pulled

정답

k set image pod/nginx nginx=nginx:1.24.0

Get nginx pod's ip created in previous step, use a temp busybox image to wget its '/'

정답

kubectl get po -o wide # get the IP, will be something like '10.1.1.131'
# create a temp busybox pod
kubectl run busybox --image=busybox --rm -it --restart=Never -- wget -O- 10.1.1.131:80

If pod crashed and restarted, get logs about the previous instance

정답

kubectl logs nginx -p

Execute a simple shell on the nginx pod

정답

kubectl exec -it nginx -- /bin/sh

Create a busybox pod that echoes 'hello world' and then exits

정답

kubectl run busybox --image=busybox -it --restart=Never -- echo 'hello world'

Do the same, but have the pod deleted automatically when it's completed

정답

k run busybox --image=busybox -it --rm --restart=Never -- echo 'hello world'

Create an nginx pod and set an env value as 'var1=val1'. Check the env value existence within the pod

정답

k run nginx --image=nginx --restart=Never --env=var1=val1

b. Multi-container Pods

2
Create a pod with an nginx container exposed on port 80. Add a busybox init container which downloads a page using 'echo "Test" > /work-dir/index.html'. Make a volume of type emptyDir and mount it in both containers. For the nginx container, mount it on "/usr/share/nginx/html" and for the initcontainer, mount it on "/work-dir". When done, get the IP of the created pod and create a busybox pod and run "wget -O- IP"

정답

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: box
  name: box
spec:
  initContainers: 
  - args: 
    - /bin/sh 
    - -c 
    - echo "Test" > /work-dir/index.html
    image: busybox 
    name: box 
    volumeMounts: 
    - name: vol 
      mountPath: /work-dir 
  containers:
  - image: nginx
    name: nginx
    ports:
    - containerPort: 80
    volumeMounts: 
    - name: vol 
      mountPath: /usr/share/nginx/html 
  volumes: 
  - name: vol 
    emptyDir: {}

# Apply pod
kubectl apply -f pod-init.yaml

# Get IP
kubectl get po -o wide

# Execute wget
kubectl run box-test --image=busybox --restart=Never -it --rm -- /bin/sh -c "wget -O- $(kubectl get pod box -o jsonpath='{.status.podIP}')"

# you can do some cleanup
kubectl delete po box

내가 쓴 답은 이건데... 결과가 다른지 헷갈린다

k run busybox --image=busybox -- command wget -O- 10.42.0.10

c. Pod design

Labels and Annotations

Show all labels of the pods

정답

kubectl get po --show-labels

Get the label 'app' for the pods (show a column with APP labels)

정답

kubectl get po -L app
# or
kubectl get po --label-columns=app

Add a new label tier=web to all pods having 'app=v2' or 'app=v1' labels

정답

kubectl label po -l "app in(v1,v2)" tier=web

Remove the 'app' label from the pods we created before

정답

kubectl label po -l app app-

Annotate pods nginx1, nginx2, nginx3 with "description='my description'" value

정답

kubectl annotate po nginx1 nginx2 nginx3 description='my description'

Check the annotations for pod nginx1

정답
k annoatate pod nginx1 --list

Remove the annotations for these three pods

정답
kubectl annotate po nginx{1..3} description- owner-
description랑 owner는 annotation key값 -> description랑 owner를 지운다는 것

Deployments

Check how the deployment rollout is going

정답

kubectl rollout status deploy nginx

Delete the deployment and the horizontal pod autoscaler you created

정답

hpa!!!

kubectl delete deploy nginx
kubectl delete hpa nginx

Implement canary deployment by running two instances of nginx marked as version=v1 and version=v2 so that the load is balanced at 75%-25% ratio

정답

nginx1.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-v1
spec:
  replicas: 3  # 75% weight (3 out of 4 total replicas)
  selector:
    matchLabels:
      app: nginx
      version: v1
  template:
    metadata:
      labels:
        app: nginx
        version: v1
    spec:
      containers:
        - name: nginx
          image: nginx:1.19  # v1 image
          ports:
            - containerPort: 80

nginx2.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-v2
spec:
  replicas: 1  # 25% weight (1 out of 4 total replicas)
  selector:
    matchLabels:
      app: nginx
      version: v2
  template:
    metadata:
      labels:
        app: nginx
        version: v2
    spec:
      containers:
        - name: nginx
          image: nginx:1.20  # v2 image (newer version)
          ports:
            - containerPort: 80

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx  # Selects both v1 and v2 pods
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: ClusterIP

kubectl scale --replicas=4 deploy my-app-v2
kubectl delete deploy my-app-v1

Jobs

Create a job named pi with image perl:5.34 that runs the command with arguments "perl -Mbignum=bpi -wle 'print bpi(2000)'"

정답

command는 -- 뒤에 !

kubectl create job pi  --image=perl:5.34 -- perl -Mbignum=bpi -wle 'print bpi(2000)'

Wait till it's done, get the output

정답

kubectl get po # get the pod name
kubectl logs pi-**** # get the pi numbers
kubectl delete job pi

Create a job with the image busybox that executes the command 'echo hello;sleep 30;echo world'

정답

명령어 작성법이 너무 헷갈림 ㅠㅠ

kubectl create job busybox --image=busybox -- /bin/sh -c 'echo hello;sleep 30;echo world'

Create a job but ensure that it will be automatically terminated by kubernetes if it takes more than 30 seconds to execute

정답
spec 밑에 activeDeadlineSeconds: 30 넣어주기

Create the same job, make it run 5 times, one after the other. Verify its status and delete it

정답
spec 밑에 completions:5 넣어주기

Cron jobs

Create the same cron job again, and watch the status. Once it ran, check which job ran by the created cron job. Check the log, and delete the cron job

정답

--watch 기억하기!

kubectl get cj
kubectl get jobs --watch
kubectl get po --show-labels

Create a cron job with image busybox that runs every minute and writes 'date; echo Hello from the Kubernetes cluster' to standard output. The cron job should be terminated if it takes more than 17 seconds to start execution after its scheduled time (i.e. the job missed its scheduled time).

정답

startingDeadlineSeconds: n : 크론잡이 정해진 시간에 실행되지 못하고 n초 이상 지연되면 해당 작업을 건너뜀

apiVersion: batch/v1
kind: CronJob
metadata:
  creationTimestamp: null
  name: time-limited-job
spec:
  jobTemplate:
    metadata:
      creationTimestamp: null
      name: time-limited-job
    spec:
      activeDeadlineSeconds: 12 # add this line
      template:
        metadata:
          creationTimestamp: null
        spec:
          containers:
          - args:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
            image: busybox
            name: time-limited-job
            resources: {}
          restartPolicy: Never
  schedule: '* * * * *'
status: {}

Create a cron job with image busybox that runs every minute and writes 'date; echo Hello from the Kubernetes cluster' to standard output. The cron job should be terminated if it successfully starts but takes more than 12 seconds to complete execution.

정답

activeDeadlineSeconds: n: 실행이 시작된 후 n초 이상 걸리면 걸리면 강제 중담

apiVersion: batch/v1
kind: CronJob
metadata:
  name: busybox-cronjob
spec:
  schedule: "* * * * *"  # 매 1분마다 실행
  jobTemplate:
    spec:
      activeDeadlineSeconds: 12  # 12초 이상 실행되면 강제 종료
      template:
        spec:
          containers:
            - name: busybox
              image: busybox
              command: ["/bin/sh", "-c", "date; echo Hello from the Kubernetes cluster; sleep 15"]
          restartPolicy: Never

Create a job from cronjob.

정답

--from=크론잡 !!

kubectl create job --from=cronjob/sample-cron-job sample-job

d. Configuration

ConfigMaps

Create and display a configmap from a file, giving the key 'special'

정답

from-file과 파일명 사이에 key 값 special을 넣어줌

kubectl create cm configmap4 --from-file=special=config4.txt

Create a configMap called 'options' with the value var5=val5. Create a new nginx pod that loads the value from variable 'var5' in an env variable called 'option'

정답

env의 이름을 잘 넣어주자
참고
https://kubernetes.io/docs/concepts/configuration/configmap/

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env:
    - name: option # name of the env variable
      valueFrom:
        configMapKeyRef:
          name: options # name of config map
          key: var5 # name of the entity in config map
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

Create a configMap 'cmvolume' with values 'var8=val8', 'var9=val9'. Load this as a volume inside an nginx pod on path '/etc/lala'. Create the pod and 'ls' into the '/etc/lala' directory.

참고

kubectl create configmap cmvolume --from-literal=var8=val8 --from-literal=var9=val9

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  volumes: # add a volumes list
  - name: myvolume # just a name, you'll reference this in the pods
    configMap:
      name: cmvolume # name of your configmap
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    volumeMounts: # your volume mounts are listed here
    - name: myvolume # the name that you specified in pod.spec.volumes.name
      mountPath: /etc/lala # the path inside your container
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

kubectl create -f pod.yaml
kubectl exec -it nginx -- /bin/sh
cd /etc/lala
ls # will show var8 var9
cat var8 # will show val8

Limit Ranges

Create a namespace named limitrange with a LimitRange that limits pod memory to a max of 500Mi and min of 100Mi

정답

네임스페이스를 만들고 만든 네임스페이스에 limit range를 적용한다
type에 어떤거에 적용할지 써준다 -> 여기서는 pod

kubectl create ns limitrange


apiVersion: v1
kind: LimitRange
metadata:
  name: ns-memory-limit
  namespace: limitrange
spec:
  limits:
  - max: # max and min define the limit range
      memory: "500Mi"
    min:
      memory: "100Mi"
    type: Pod

Create an nginx pod that requests 250Mi of memory in the limitrange namespace

정답

나는 처음에 limits: 부분을 안넣고 만들었는데 그랬더니 이런 에러가 났다 -> 네임스페이스에 정한 limit를 넣어준다!

Error from server (Forbidden): error when creating "5.yaml": pods "nginx" is forbidden: maximum memory usage per Pod is 500Mi.  No limit is specified

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
  namespace: limitrange
spec:
  containers:
  - image: nginx
    name: nginx
    resources:
      requests:
        memory: "250Mi"
      limits:
        memory: "500Mi" # limit has to be specified and be <= limitrange
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

Secrets

Delete the pod you just created and mount the variable 'username' from secret mysecret2 onto a new nginx pod in env variable called 'USERNAME'

정답

spec.env.name = 문제에서 요구한 env variable의 이름
spec.env.valueFrom.secretKeyRef.name: 앞서 만든 시크릿 명
spec.env.valueFrom.secretKeyRef.key: 시크릿의 키값

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env: # our env variables
    - name: USERNAME # asked name
      valueFrom:
        secretKeyRef: # secret reference
          name: mysecret2 # our secret's name
          key: username # the key of the data in the secret
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

Consuming the Secret. Create a Pod named 'consumer' with the image 'nginx' in the namespace 'secret-ops' and consume the Secret as an environment variable. Then, open an interactive shell to the Pod, and print all environment variables.

정답

valueFrom를 쓰는건지 envFrom을 쓰는건지 조금 헷갈린다 ㅠ

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: consumer
  name: consumer
  namespace: secret-ops
spec:
  containers:
  - image: nginx
    name: consumer
    resources: {}
    env:
    - name: API_KEY
      valueFrom:
        secretKeyRef:
          name: ext-service-secret
          key: API_KEY
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

k exec -it -n secret-ops consumer -- /bin/sh
#env

ServiceAccounts

Generate an API token for the service account 'myuser'

정답

kubectl create token myuser

e. Observability

Liveness, readiness and startup probes

Lots of pods are running in qa,alan,test,production namespaces. All of these pods are configured with liveness probe. Please list all pods whose liveness probe are failed in the format of <namespace>/<pod name> per line.

정답

  kubectl get events -o json | jq -r '.items[] | select(.message | contains("Liveness probe failed")).involvedObject | .namespace + "/" + .name'

풀이

Liveness Probe란?
Kubernetes에서 Pod가 정상적으로 실행되고 있는지 체크하는 방법 중 하나.
실패하면 Kubelet이 자동으로 컨테이너를 재시작함.
Liveness Probe는 exec, HTTP GET, TCP Socket 등의 방식으로 Pod의 정상 여부를 검사할 수 있음.
Liveness Probe 실패 시 발생하는 이벤트 예시

LAST SEEN   TYPE      REASON      OBJECT              MESSAGE
22m         Warning   Unhealthy   pod/liveness-exec   Liveness probe failed: cat: can't open '/tmp/healthy': No such file or directory

→ 여기서 중요한 부분은 "Liveness probe failed"라는 메시지가 이벤트 로그에 남는다는 점!

kubectl get events -o json
- kubectl get events는 Kubernetes 클러스터에서 발생한 모든 이벤트를 조회하는 명령어
- -o json 옵션을 추가하면 출력을 JSON 형식으로 반환
jq -r '.items[] | select(.message | contains("Liveness probe failed"))'
- jq는 JSON 데이터를 필터링하는 명령어.
- select(.message | contains("Liveness probe failed")) → "Liveness probe failed"가 포함된 이벤트만 선택
| .involvedObject | .namespace + "/" + .name'
- .involvedObject 필드에서 .namespace와 .name을 가져와 출력 형식을 /으로 변환.

Debugging

Create a busybox pod that runs 'notexist'. Determine if there's an error (of course there is), see it. In the end, delete the pod forcefully with a 0 grace period

정답

kubectl delete po busybox --force --grace-period=0

풀이

--grace-period=0 옵션은 Pod이 정상적으로 종료될 시간을 주지 않고, 즉시 강제 종료하는 역할

f. Services

Create a pod with image nginx called nginx and expose its port 80

정답

kubectl run nginx --image=nginx --restart=Never --port=80 --expose

풀이

새로운 Pod을 만들면서 동시에 Service를 만들고 싶을 때
- kubectl run nginx --image=nginx --restart=Never --port=80 --expose
이미 존재하는 Pod을 서비스로 노출하고 싶을 때
- kubectl expose pod nginx --port=80
여러 개의 Pod(Deployment 등)을 Service로 노출하고 싶을 때
- kubectl expose deployment my-deployment --port=80 --type=LoadBalancer

Confirm that ClusterIP has been created. Also check endpoints

정답

kubectl get svc nginx # services
kubectl get ep # endpoints

Get service's ClusterIP, create a temp busybox pod and 'hit' that IP with wget

정답

controlplane ~ ➜  k get svc nginx
NAME    TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
nginx   ClusterIP   10.43.23.205   <none>        80/TCP    3m30s

controlplane ~ ✖ k run busybox1 --rm --image=busybox -it --r
estart=Never -- wget -O- 10.43.23.205:80
Connecting to 10.43.23.205:80 (10.43.23.205:80)
writing to stdout
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
-                    100% |********************************|   615  0:00:00 ETA
written to stdout
pod "busybox1" deleted

풀이

kubectl run busybox: busybox라는 Pod을 실행
--rm: Pod 실행 후 자동 삭제 (임시 Pod)
--image=busybox: busybox 이미지를 사용
-it: 인터랙티브 모드 (stdin 및 tty 사용)
--restart=Never: 단일 Pod 실행
-- wget -O- 10.108.93.130:80: busybox 내부에서 wget 실행하여 nginx 서비스에 요청
- wget -O-: 웹페이지(응답)를 표준 출력(stdout)에 바로 출력하는 옵션
- 10.108.93.130:80 → 앞에서 얻은 ClusterIP에 요청을 보냄

Convert the ClusterIP to NodePort for the same service and find the NodePort port. Hit service using Node's IP. Delete the service and the pod at the end.

정답

ClusterIP에서 NodePort로 변경

controlplane ~ ➜  k get svc nginx -o yaml > np.yaml

controlplane ~ ➜  vi np.yaml 

controlplane ~ ➜  k apply -f np.yaml 
Warning: resource services/nginx is missing the kubectl.kubernetes.io/last-applied-configuration annotation which is required by kubectl apply. kubectl apply should only be used on resources created declaratively by either kubectl create --save-config or kubectl apply. The missing annotation will be patched automatically.
service/nginx configured

controlplane ~ ➜  cat np.yaml 
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2025-02-15T07:37:54Z"
  name: nginx
  namespace: default
  resourceVersion: "1251"
  uid: 9a04bd45-a6ae-4c65-97f5-d61f72767758
spec:
  clusterIP: 10.43.23.205
  clusterIPs:
  - 10.43.23.205
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    run: nginx
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}

서비스가 있는 노드 ip찾기

controlplane ~ ➜  k get node -o wide
NAME           STATUS   ROLES                  AGE   VERSION        INTERNAL-IP       EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION    CONTAINER-RUNTIME
controlplane   Ready    control-plane,master   44m   v1.31.0+k3s1   192.168.211.162   <none>        Alpine Linux v3.16   5.15.0-1071-gcp   containerd://1.7.20-k3s1

controlplane ~ ➜  wget -O- 192.168.211.162:30100
--2025-02-15 07:54:41--  http://192.168.211.162:30100/
Connecting to 192.168.211.162:30100... connected.
HTTP request sent, awaiting response... 200 OK
Length: 615 [text/html]
Saving to: 'STDOUT'

-                0%[     ]       0  --.-KB/s               <!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
-              100%[====>]     615  --.-KB/s    in 0s      

2025-02-15 07:54:41 (112 MB/s) - written to stdout [615/615]

Create a deployment called foo using image 'dgkanatsios/simpleapp' (a simple server that returns hostname) and 3 replicas. Label it as 'app=foo'. Declare that containers in this pod will accept traffic on port 8080 (do NOT create a service yet)

정답

kubectl create deploy foo --image=dgkanatsios/simpleapp --port=8080 --replicas=3
kubectl label deployment foo --overwrite app=foo

kubectl run busybox --image=busybox --restart=Never -it --rm -- sh 요게 맨날 헷갈린다 ㅠㅠ

kubectl get pods -l app=foo -o wide # 'wide' will show pod IPs
kubectl run busybox --image=busybox --restart=Never -it --rm -- sh
wget -O- <POD_IP>:8080 # do not try with pod name, will not work
# try hitting all IPs generated after running 1st command to confirm that hostname is different
exit

Create an nginx deployment of 2 replicas, expose it via a ClusterIP service on port 80. Create a NetworkPolicy so that only pods with labels 'access: granted' can access the pods in this deployment and apply it

정답

kubectl create deployment nginx --image=nginx --replicas=2
kubectl expose deployment nginx --port=80
controlplane ~ ➜  kubectl describe svc nginx
Name:                     nginx
Namespace:                default
Labels:                   app=nginx
Annotations:              <none>
Selector:                 app=nginx
Type:                     ClusterIP
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.43.243.140
IPs:                      10.43.243.140
Port:                     <unset>  80/TCP
TargetPort:               80/TCP
Endpoints:                10.42.0.14:80,10.42.0.15:80
Session Affinity:         None
Internal Traffic Policy:  Cluster
Events:                   <none>

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: access-nginx # pick a name
spec:
  podSelector:
    matchLabels:
      app: nginx # selector for the pods
  ingress: # allow ingress traffic
  - from:
    - podSelector: # from pods
        matchLabels: # with this label
          access: granted

g. State Persistence

Create busybox pod with two containers, each one will have the image busybox and will run the 'sleep 3600' command. Make both containers mount an emptyDir at '/etc/foo'. Connect to the second busybox, write the first column of '/etc/passwd' file to '/etc/foo/passwd'. Connect to the first busybox and write '/etc/foo/passwd' file to standard output. Delete pod.

정답

파드 생성
- 두 컨테이너는 sleep 3600명령어 실행, empty dir 볼륨 마운트

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  dnsPolicy: ClusterFirst
  restartPolicy: Never
  containers:
  - args:
    - /bin/sh
    - -c
    - sleep 3600
    image: busybox
    imagePullPolicy: IfNotPresent
    name: busybox
    resources: {}
    volumeMounts: #
    - name: myvolume #
      mountPath: /etc/foo #
  - args:
    - /bin/sh
    - -c
    - sleep 3600
    image: busybox
    name: busybox2 # don't forget to change the name during copy paste, must be different from the first container's name!
    volumeMounts: #
    - name: myvolume #
      mountPath: /etc/foo #
  volumes: #
  - name: myvolume #
    emptyDir: {} #

두번째 컨테이너 접속

kubectl exec -it busybox -c busybox2 -- /bin/sh

/etc/passwd 파일의 첫번째 열만가져와 /etc/foo/passwd에 저장
- cut -f 1 -d ':': :(콜론) 기준으로 데이터를 나누고, 첫 번째 필드만 가져옴
  - cut: 특정 필드(열)을 잘라서 출력하는 명령어
  - -d ':' 콜론을 구분자로 사용
  - -f 1 첫번째 필드(열)만 출력

cat /etc/passwd | cut -f 1 -d ':' > /etc/foo/passwd

저장된 내용 확인

cat /etc/foo/passwd

첫번째 컨테이너 접속

kubectl exec -it busybox -c busybox -- /bin/sh

empty dir 볼륨이 잘 마운트되었는지 확인

mount | grep foo

내용 출력

cat /etc/foo/passwd

컨테이너에 접근할때 명령어 kubectl exec busybox -it -- /bin/sh

✅ emptyDir는 Pod 내부 컨테이너 간 공유 가능하지만, Pod을 넘어서 공유 불가
✅ hostPath는 같은 노드 내에서만 공유 가능
✅ PersistentVolume + PVC를 사용하면 멀티 노드에서도 공유 가능 (외부 스토리지 필요)

Create a busybox pod with 'sleep 3600' as arguments. Copy '/etc/passwd' from the pod to your local folder

정답

kubectl cp: 로컬 파잃 <-> 파드 간 파일 복사할 때 사용하는 명령어

kubectl run busybox --image=busybox --restart=Never -- sleep 3600
kubectl cp busybox:/etc/passwd ./passwd 
cat passwd

h. Helm

CKAD 시험에서만 helm docs를 들어갈 수 있다! -> https://helm.sh/docs/
출처: https://docs.linuxfoundation.org/tc-docs/certification/certification-resources-allowed#certified-kubernetes-administrator-cka-and-certified-kubernetes-application-developer-ckad

Find pending Helm deployments on all namespaces

정답

helm list --pending -A

참고
https://helm.sh/docs/helm/helm_list/#helm

Write the contents of the values.yaml file of the bitnami/node chart to standard output

정답

helm show values bitnami/node

Install the bitnami/node chart setting the number of replicas to 5

replica가 쓰인 부분 찾기

controlplane $ helm show values bitnami/node | grep -i replica
## @param replicaCount Specify the number of replicas for the application
replicaCount: 1

values 파일을 수정하거나 set 명령어 사용

helm install mynode bitnami/node --set replicaCount=5

hyereen

이전 포스트

KILLERCODA - CKAD - Api Deprecations 오답노트

다음 포스트