[CKA] Practice Test - Commands And Arguments

CKA (https://www.credly.com/org/the-linux-foundation/badge/cka-certified-kubernetes-administrator)

문제1

How many PODs exist on the system?

In the current(default) namespace

 

풀이

controlplane ~ ➜  k get po
NAME             READY   STATUS    RESTARTS   AGE
ubuntu-sleeper   1/1     Running   0          2m7s

문제2

What is the command used to run the pod ubuntu-sleeper?

 

풀이

controlplane ~ ➜  k get po -o jsonpath='{..command}'
["sleep","4800"]

 

문제3

Create a pod with the ubuntu image to run a container to sleep for 5000 seconds. Modify the file ubuntu-sleeper-2.yaml.
Note: Only make the necessary changes. Do not modify the name.

 

풀이

controlplane ~ ➜  vi ubuntu-sleeper-2.yaml 

apiVersion: v1
kind: Pod 
metadata:
  name: ubuntu-sleeper-2
spec:
  containers:
  - name: ubuntu
    image: ubuntu

• 기존에 이 내용 이었음

apiVersion: v1
kind: Pod 
metadata:
  name: ubuntu-sleeper-2
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
    - sleep
    - "5000"

 

문제4

Create a pod using the file named ubuntu-sleeper-3.yaml. There is something wrong with it. Try to fix it!

Pod Name: ubuntu-sleeper-3
Command: sleep 1200

 

풀이

apiVersion: v1
kind: Pod 
metadata:
  name: ubuntu-sleeper-3
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
      - "sleep"
      - 1200

• 기존에 위와 같은 내용

apiVersion: v1
kind: Pod 
metadata:
  name: ubuntu-sleeper-3
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
      - sleep
      - "1200"

 

문제5

Update pod ubuntu-sleeper-3 to sleep for 2000 seconds.

Pod Name: ubuntu-sleeper-3
Command: sleep 2000

 

풀이

---
spec:
  containers:
  - command:
    - sleep
    - "2000"
    image: ubuntu
---

• 위와 같이 yaml 파일 command 부분을 수정해주고 파드 삭제 후 재생성 해줌

 

문제6

Inspect the file Dockerfile given at /root/webapp-color directory. What command is run at container startup?

 

풀이

controlplane ~ ➜  cat /root/webapp-color/Dockerfile
FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

ENTRYPOINT ["python", "app.py"]

• 커맨드는 python app.py임

 

문제7

Inspect the file Dockerfile2 given at /root/webapp-color directory. What command is run at container startup?

 

풀이

controlplane ~ ➜  cat /root/webapp-color/Dockerfile2
FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

ENTRYPOINT ["python", "app.py"]

CMD ["--color", "red"]

• 컨테이너가 시작되면 ENTRYPOINT 가 먼저 수행되고 CMD는 인자 값으로 제공됨
• 정답은 python app.py --color red

 

문제8

Inspect the two files under directory webapp-color-2. What command is run at container startup?

 

풀이

controlplane ~/webapp-color-2 ➜  ls
Dockerfile             webapp-color-pod.yaml

controlplane ~/webapp-color-2 ➜  cat *
FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

ENTRYPOINT ["python", "app.py"]

CMD ["--color", "red"]
apiVersion: v1 
kind: Pod 
metadata:
  name: webapp-green
  labels:
      name: webapp-green 
spec:
  containers:
  - name: simple-webapp
    image: kodekloud/webapp-color
    command: ["--color","green"]

• Dockerfile에 명령어를 설정하고 Pod 에서 또 명령어를 설정한 문제임
• 헷갈리면 안되는게 커맨드는 이미지보다 파드가 우선시 됨 --color green 이 수행될것

 

문제9

Inspect the two files under directory webapp-color-3. What command is run at container startup?

Assume the image was created from the Dockerfile in this directory.

 

풀이

controlplane ~/webapp-color-3 ➜  cat *
FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

ENTRYPOINT ["python", "app.py"]

CMD ["--color", "red"]
apiVersion: v1 
kind: Pod 
metadata:
  name: webapp-green
  labels:
      name: webapp-green 
spec:
  containers:
  - name: simple-webapp
    image: kodekloud/webapp-color
    command: ["python", "app.py"]
    args: ["--color", "pink"]

• 위에서도 말했듯이 커맨드는 파드가 우선시됨 python app.py --color pink 가 실행될것

 

문제10

Create a pod with the given specifications. By default it displays a blue background. Set the given command line arguments to change it to green.

Pod Name: webapp-green

Image: kodekloud/webapp-color

Command line arguments: --color=green

 

풀이

• 처음에는 명령형으로 해결하려 했는데 이런 애매한 문제는 그냥 선언형으로 하는 게 맞는듯
• piVersion: v1 kind: Pod metadata: creationTimestamp: null labels: run: webapp-green name: webapp-green spec: containers: - args: - --color - green image: kodekloud/webapp-color name: webapp-green resources: {} dnsPolicy: ClusterFirst restartPolicy: Always status: {}
• args를 설정해줘서 command line의 인자 값을 설정해줌