[cka] kodecloud PODs 생성하기.

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

 

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

$ controlplane ~ ➜  kubectl get pods
No resources found in default namespace.

 

2. Create a new pod with the nginx image.

2-1 ) kubectl run 활용

# kubectl run <pods명> --image <사용이미지>
$ kubectl run nginx-pods --image nginx

 

2-2 ) yaml 로 실행

-- nginx-pods.yaml

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: nginx
  name: nginx-pods
spec:
  containers:
  - image: nginx
    name: nginx

 

2-3) yaml 파일적용

$ kubectl apply -f nginx-pods.yaml

 

 

ps) yaml 쉽게 만드는 방법 - --dry-run=client -o yaml 옵션사용

$ kubectl run nginx-pods --image nginx --dry-run=client -o yaml

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx-pods
  name: nginx-pods
spec:
  containers:
  - image: nginx
    name: nginx-pods
    resources: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

 

 

https://kubernetes.io/docs/reference/kubectl/generated/kubectl_run/#synopsis

kubectl run

 

 

3. How many pods are created now? Note: We have created a few more pods. So please check again.

$ controlplane ~ ➜  k get pods
NAME            READY   STATUS    RESTARTS   AGE
nginx           1/1     Running   0          13s
newpods-krwlt   1/1     Running   0          4s
newpods-zj5jt   1/1     Running   0          4s
newpods-hjqcn   1/1     Running   0          4s

 

answer : 4

 

4. What is the image used to create the new pods? You must look at one of the new pods in detail to figure this out.

 

## pods 정보확인하기
$ kubectl describe pods <파드명> -n <namespace>

$ kubectl describe pods newpods-krwlt


...중략

Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  2m42s  default-scheduler  Successfully assigned default/newpods-krwlt to controlplane
  Normal  Pulling    2m43s  kubelet            Pulling image "busybox"
  Normal  Pulled     2m42s  kubelet            Successfully pulled image "busybox" in 325ms (325ms including waiting)

 

answer: busybox

 

5. Which nodes are these pods placed on? You must look at all the pods in detail to figure this out.

 

# 파드 정보를 더 자세히 보기 '-o wide' 옵션 사용.
$ kubectl get pods -o wide 

$ controlplane ~ ✖ k get pods -o wide
NAME            READY   STATUS    RESTARTS   AGE     IP           NODE           NOMINATED NODE   READINESS GATES
nginx           1/1     Running   0          3m57s   10.42.0.9    controlplane   <none>           <none>
newpods-krwlt   1/1     Running   0          3m48s   10.42.0.10   controlplane   <none>           <none>
newpods-zj5jt   1/1     Running   0          3m48s   10.42.0.11   controlplane   <none>           <none>
newpods-hjqcn   1/1     Running   0          3m48s   10.42.0.12   controlplane   <none>           <none>

 

 

answer: controlplane

 

6.How many containers are part of the pod webapp?
Note: We just created a new POD. Ignore the state of the POD for now.

 

controlplane ~ ➜  k get pods
NAME            READY   STATUS             RESTARTS   AGE
nginx           1/1     Running            0          5m29s
newpods-krwlt   1/1     Running            0          5m20s
newpods-zj5jt   1/1     Running            0          5m20s
newpods-hjqcn   1/1     Running            0          5m20s
webapp          1/2     ImagePullBackOff   0          26s

 

answer : 2

 

7. What images are used in the new webapp pod?
You must look at all the pods in detail to figure this out.

 

$ kubectl describe pods webapp

...중략

Events:
  Type     Reason     Age                From               Message
  ----     ------     ----               ----               -------
  Normal   Scheduled  86s                default-scheduler  Successfully assigned default/webapp to controlplane
  Normal   Pulling    86s                kubelet            Pulling image "nginx"
  Normal   Pulled     86s                kubelet            Successfully pulled image "nginx" in 224ms (224ms including waiting)
  Normal   Created    86s                kubelet            Created container nginx
  Normal   Started    86s                kubelet            Started container nginx
  Normal   Pulling    46s (x3 over 86s)  kubelet            Pulling image "agentx"
  Warning  Failed     40s (x3 over 85s)  kubelet            Failed to pull image "agentx": failed to pull and unpack image "docker.io/library/agentx:latest": failed to resolve reference "docker.io/library/agentx:latest": pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed
  Warning  Failed     40s (x3 over 85s)  kubelet            Error: ErrImagePull
  Normal   BackOff    2s (x5 over 85s)   kubelet            Back-off pulling image "agentx"
  Warning  Failed     2s (x5 over 85s)   kubelet            Error: ImagePullBackOff

 

answer : nginx and agentx

 

8. What is the state of the container agentx in the pod webapp?
Wait for it to finish the ContainerCreating state

 

answer : error or waiting -> 위 describe 정보에서 참조. 

 

9. Why do you think the container agentx in pod webapp is in error?
Try to figure it out from the events section of the pod.

 

-> 위 Message 에서 agentx 이미지에 대해 'failed to pull and unpack image' 메시지 남음.

 

answer : A Docker image with this name dosen't exist on Docker Hub

 

10. What does the READY column in the output of the kubectl get pods command indicate?

$ controlplane ~ ➜  k get pods
NAME            READY   STATUS             RESTARTS   AGE
...
webapp          1/2     ImagePullBackOff   0          4m57s
#.          실행중/전체

answer: Running Container in POD/Total Containers in POD


11. Delete the webapp Pod.
Once deleted, wait for the pod to fully terminate.

 

# pod 삭제하기
# kubectl delete pods <파드명>
$ kubectl delete pods webapp

 

12. 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!

 

# redis123-pods.yaml

apiVersion: v1
kind: Pod
metadata:
  name: redis
spec:
  containers:
  - image: redis123
    name: redis
    


$ kubectl apply -f redis123-pods.yaml

 

 

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

 

13-1. yaml 수정후 apply 로 적용.

 

# redis123-pods.yaml 파일 수정

apiVersion: v1
kind: Pod
metadata:
  name: redis
spec:
  containers:
  - image: redis
    name: redis

$ kubectl delete pods redis
$ kubectl apply -f redis123-pods.yaml

# 또는 --force 옵션 추가

$ kubectl apply -f redis123-pods.yaml --force

 

13-2. kubectl edit 이용

 

$ kubectl edit pods redis

### edit 파일

 Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
kind: Pod
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"redis","namespace":"default"},"spec":{"containers":[{"image":"redis","name":"redis"}]}}
  creationTimestamp: "2024-05-27T14:09:36Z"
  name: redis
  namespace: default
  resourceVersion: "1525"
  uid: 7b318f8b-64b7-4077-b655-6f98e42f5b2e
spec:
  containers:
  - image: redis123 #### 해당 이미지 변경후 저장.
    imagePullPolicy: Always
    name: redis
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-jzthm
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: controlplane