[CKA] Pod 란?

개인적으로 CKA(Certified Kubernetes Administrator) 시험을 준비하고 있는데, 이를 위해 개념 및 관련 문제를 정리하고자 한다.

 

1. 정의

- 1개 이상의 컨테이너가 함께 묶여서 동작하는 그룹

 

2. 특징

- 공유 네트워크

  > Pod 내부 컨테이너들은 동일한 네트워크 네임스페이스를 공유

- 공유 스토리지

  > Pod 에 Volume 을 붙이고 여러 컨테이너가 같은 Volume 을 마운트 해 사용

- 라이프사이클 단위

  > Pod 는 하나의 단위로 생성되고 삭제됨

 

3. 관련 문제 (KodeKloud 에서 제공하는 샘플 문제를 정리)

- How many pods exist on the system?

  > In the current(default) namespace.

kubectl get pods

 

- Create a new pod using the nginx image.

  > Image name: nginx

kubectl run nginx-pod --image=nginx

 

- Which image is specified for the pods whose names begin with the newpods- prefix?

  > You must look at one of the new pods in detail to figure this out.

kubectl get pods -o name | grep new pods
kubectl describe pod <pod-name>

 

- Which nodes are these pods placed on?

  > You must look at all the pods in detail to figure this out.

kubectl get nodes

 

- We just created a new pod named webapp. How many containers are part of the webapp pod.

  > Note: Ignore the state of the pod for now.

kubectl describe pod webapp

 

- What does the READY column in the output of the ‘kubectl get pods’ command indicate?

  답) Running Containers in POD / Total Containers in POD

 

- Delete the webapp pod. 

  > Once deleted, wait for the pod to fully terminate.

kubectl delete pod webapp

 

- Create a new pod with the name ‘redis’ and the image ‘redis123’

  > Use a pod-definition YAML file. And yes the image name is wrong!

kubectl run redis —image=redis123 --dry-run=client -o yaml > redis-definition.yaml 
kubectl create -f redis-definition.yaml

 

- Now change the image on this pod to ‘redis’. - Once done, the pod should be in a running state.

(redis-definition.yaml 파일을 직접 수정 후) kubectl apply -f redis-definition.yaml

 

- Create a new pod called custom-nginx using the nginx image and run it on container port 8080.

kubectl run custom-nginx --image=nginx --port=8080

 

4. 출처

- https://learn.kodekloud.com/user/courses/udemy-labs-certified-kubernetes-administrator-with-practice-tests