[cka] Commands and Arguments

1. How many PODs exist on the system?
In the current(default) namespace

 

controlplane ~ ➜  k get pods
NAME             READY   STATUS    RESTARTS   AGE
ubuntu-sleeper   1/1     Running   0          38s

 

answer : 1

 

 

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

 

controlplane ~ ➜  k describe pod ubuntu-sleeper
Name:             ubuntu-sleeper
Namespace:        default
Priority:         0
...
Containers:
  ubuntu:
    Container ID:  containerd://a4e73c5a4f31185f4da9de660223023800562459920577e2a46e9007f9a6225a
    Image:         ubuntu
    Image ID:      docker.io/library/ubuntu@sha256:2e863c44b718727c860746568e1d54afd13b2fa71b160f5cd9058fc436217b30
    Port:          <none>
    Host Port:     <none>
    Command:
      sleep
      4800
    State:          Running

 

answer : sleep 4800

 

3. 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.

 

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: ubuntu-sleeper-2
  name: ubuntu-sleeper-2
spec:
  containers:
  - command:
      - "sleep"
      - "5000"
    image: ubuntu
    name: ubuntu-sleeper-2
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

 

 

4. Create a pod using the file named ubuntu-sleeper-3.yaml. There is something wrong with it. Try to fix it!
Note: Only make the necessary changes. Do not modify the name.

 

apiVersion: v1
kind: Pod 
metadata:
  name: ubuntu-sleeper-3
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
      - "sleep"
      - 1200    # -> "2000" 문자열로 변경

 

5. Update pod ubuntu-sleeper-3 to sleep for 2000 seconds.
Note: Only make the necessary changes. Do not modify the name of the pod. Delete and recreate the pod if necessary.

controlplane ~ ➜  k edit pod ubuntu-sleeper-3
###
apiVersion: v1
kind: Pod
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"ubuntu
-sleeper-3","namespace":"default"},"spec":{"containers":[{"command":["sleep","120
0"],"image":"ubuntu","name":"ubuntu"}]}}
  creationTimestamp: "2024-07-02T14:56:52Z"
  name: ubuntu-sleeper-3
  namespace: default
  resourceVersion: "1059"
  uid: fef83136-bac2-4503-81d5-35d94cca40f0
spec:
  containers:
  - command:
    - sleep
    - "1200"   # -> "2000" 변경
    
    ##
    
    
 controlplane ~ ➜  k edit pod ubuntu-sleeper-3 
error: pods "ubuntu-sleeper-3" is invalid
A copy of your changes has been stored to "/tmp/kubectl-edit-1264881946.yaml"
error: Edit cancelled, no valid changes were saved.


controlplane ~ ✖ k apply -f /tmp/kubectl-edit-1264881946.yaml --force
pod/ubuntu-sleeper-3 configured

 

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

FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

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

 

answer: python app.py

 

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

FROM python:3.6-alpine

RUN pip install flask

COPY . /opt/

EXPOSE 8080

WORKDIR /opt

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

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

 

answer : python app.py --color red

 

8. Inspect the two files under directory webapp-color-2. What command is run at container startup?
Assume the image was created from the Dockerfile in this directory.

 

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

 

answer : --color green

 

9.  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.

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"]

 

answer python app.py --color pink

 

10. 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.

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

 

 

args / command 차이

 

command

 

command 필드는 Docker 이미지의 ENTRYPOINT를 재정의하는 데 사용됩니다. 이는 컨테이너가 시작될 때 실행할 실행 파일을 지정합니다.

 

args

 

args 필드는 command에 제공되는 인수를 지정합니다. command가 지정되지 않은 경우, args는 Docker 이미지의 기본 ENTRYPOINT에 제공됩니다.

 

두 필드의 동작 방식

 

• command와 args가 모두 지정된 경우, 컨테이너는 지정된 command와 제공된 args를 사용하여 실행됩니다.

• command만 지정된 경우, 컨테이너는 인수 없이 지정된 command를 실행합니다.

• args만 지정된 경우, 컨테이너는 Docker 이미지의 기본 ENTRYPOINT에 제공된 args를 사용하여 실행됩니다.