CKA 문제

1. ETCD Backup & Restore

Question : ETCD Backup & Restore

TASK :

First, create a snapshop of the existing etcd instance running at https://127.0.0.1:2379, saving the snapshot to /data/etcd-snapshot.db.

Next, restore and existing, previous snapshot located at /data/etcd-snapshot-previous.db.

The following TLS certificates/key are supplied for connecting to the server with etcdctl:

CA certificate : /etc/kubernetes/pki/etcd/ca.crt

Client certificate : /etc/kubernetes/pki/etcd/server.crt

Client key : /etc/kubernetes/pki/etcd/server.key

2. pod 생성하기

Question : Create a new namespace and create a pod in the namespace

TASK :

namespace name : 본인 namespace ( edu1 ~ 21 )

pod name : eshop-main

image : ghcr.io/shclub/busybox:1.28

env : DB=mysql

결과값

ubuntu@edu-k8s:~/$ kubectl exec -it eshop-main   -- printenv
DB=mysql

3. Static POD 생성하기

Master Node의 API를 호출 하지 않아 Scheduler 가 생성하지 않는 POD 이며 각 Node의 kubelet ( Daemon ) 이 생성한다.

k8s에는 /var/lib/kubelet/config.yaml 에서 static POD yaml 화일을 위치를 볼수 있고 일반적으로 /etc/kubernetes/manifests 폴더에 있다.

ubuntu@edu-k8s:~/$ cat /var/lib/kubelet/config.yaml 
...
staticPodPath: /etc/kubernetes/manifests
...

Master Node 의 POD 들도 Static POD 이고 kubelet 에 의해서 기동된다.

Question : Configure kubelet hosting to start a pod on > the node

TASK :

Node : edu-k8s.worker01 ( okd 이면 : edu.worker05 )

Pod Name : <edu+순번>-web ( 예, edu1-web )

image : ghcr.io/shclub/nginx

결과값

ubuntu@edu-k8s:~/$ kubectl get po -n default
default                                            web-edu.node01                                                  1/1     Running                0          2m54s

4. Multi Container POD 생성하기

하나의 POD에 Container를 여러개 생성 할 수 있다.

Question : Create Pod

TASK :

Create a pod name multi-con with 3 containers running : nginx, redis, memcached

image : ghcr.io/shclub/nginx , ghcr.io/shclub/redis, ghcr.io/shclub/memcached

결과값

ubuntu@edu-k8s:~/$ kubectl get po
NAME                                READY   STATUS    RESTARTS   AGE
multi-con                           3/3     Running   0          31s
ubuntu@edu-k8s:~/$ kubectl describe po multi-con
Name:         multi-con
Namespace:    edu30
Priority:     0
Node:         edu.worker02/172.25.1.50
Start Time:   Fri, 23 Sep 2022 20:47:25 +0900
Labels:       run=multi-con
...
Containers:
  nginx:
    Container ID:   cri-o://8594ed5595f6d8049fd8368473706d147fc1d48ebd2fc53f338393d97de35cdd
    Image:          ghcr.io/shclub/nginx
    Image ID:       docker.io/library/nginx@sha256:79c77eb7ca32f9a117ef91bc6ac486014e0d0e75f2f06683ba24dc298f9f4dd4
    Port:           <none>
...
  redis:
    Container ID:   cri-o://56b3d75c4491df928ef66d1077077c2e3c0bcc12559e62a8b220b1f4bcc46c01
    Image:          ghcr.io/shclub/redis
    Image ID:       docker.io/library/redis@sha256:b4e56cd71c74e379198b66b3db4dc415f42e8151a18da68d1b61f55fcc7af3e0
...
  memcached:
    Container ID:   cri-o://0e11b71e73894b5b69bba208eb7dc9c669dc635af982fe8121b02806f50ab5e3
    Image:          ghcr.io/shclub/memcached
    Image ID:       docker.io/library/memcached@sha256:324479339ef09ec98467d7c0a8083909503e7af3095390614990af0fee781c7b
...
  Normal  Pulling         2m26s  kubelet            Pulling image "nginx"
  Normal  Pulled          2m22s  kubelet            Successfully pulled image "ghcr.io/shclub/nginx" in 4.018533684s
  Normal  Created         2m22s  kubelet            Created container nginx
  Normal  Started         2m22s  kubelet            Started container nginx
  Normal  Pulling         2m22s  kubelet            Pulling image "redis"
  Normal  Pulled          2m12s  kubelet            Successfully pulled image "ghcr.io/shclub/redis" in 10.541276692s
  Normal  Started         2m11s  kubelet            Started container redis
  Normal  Pulling         2m11s  kubelet            Pulling image "memcached"
  Normal  Created         2m11s  kubelet            Created container redis
  Normal  Pulled          2m2s   kubelet            Successfully pulled image "ghcr.io/shclub/memcached" in 9.577820141s
  Normal  Created         2m2s   kubelet            Created container memcached
  Normal  Started         2m2s   kubelet            Started container memcached

5. Side-car container POD 실행

기존 POD에 로그 분석을 위한 별도 Container 를 Side Car 로 추가할 수 있다.

Question : An existing Pod needs to be integrated into the K8s built-in logging architecture (e.g. kubectl logs )
Adding a streaming sidecar container is good and common way to accomplish this requirement.

TASK :

Add a sidecard container named sidecar, using ghcr.io/shclub/busybox image, to the existing Pod eshop-cart-app.

The new sidecar container has to run the following command: /bin/sh -c 'tail -n +1 -F /var/log/cart-app.log'

Use a Volume mounted at /var/log, to make the log file cart-app.log avaiable to the sidecar container.

Don't modify the eshop-cart-app

일단 기동 중인 eshop-cart-app 라는 pod에서 yaml 화일을 받아 옵니다.
( 우리는 현재 기동한 POD가 없기 때문에 아래 yaml를 사용한다. )

kubectl get po eshop-cart-app -o yaml > eshop.yaml
( default namespace에 eshop-cart-app pod 있음. )

eshop.yaml

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: eshop-cart-app
  name: eshop-cart-app
spec:
  containers:
  - command:
    - /bin/sh
    - -c
    - 'i=1;while :;do echo -e "$i: price: $((RANDOM % 10000 +1))" >> /var/log/cart-app.log; i=$((i+1)); sleep 2;done'
    image: ghcr.io/shclub/busybox
    name: eshop-cart-app
    volumeMounts:
    - mountPath: /var/log
      name: varlog
  volumes:
  - emptyDir: {}
    name: varlog

결과값

ubuntu@edu-k8s:~/$ kubectl get po 
NAME                                READY   STATUS    RESTARTS   AGE
eshop-cart-app                      2/2     Running   0          11s

sidecar 컨테이너에서 로그 정보가 나와야 한다.

ubuntu@edu-k8s:~/$ kubectl logs eshop-cart-app -c sidecar
1: price: 9448
2: price: 5839
3: price: 7135
4: price: 9062
5: price: 2709
6: price: 348
7: price: 9538
8: price: 356
9: price: 5786
...

6. Deployment & Pod Scale

1. Pod scale out

Question : Expand the number of running Pods in eshop-order from 1 to 5.

TASK :

namespace : 본인 namespace

deployment : eshop-order

image : ghcr.io/shclub/nginx

아래 yaml 화일을 실행하여 deployment 를 생성합니다.

ubuntu@edu-k8s:~/$ kubectl create deployment eshop-order --image=ghcr.io/shclub/nginx --replicas=1

ubuntu@edu-k8s:~/$ kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
eshop-order        1/1     1            1           7s

결과값 : pod가 5개가 생성되었는지 확인한다.

ubuntu@edu-k8s:~/$ kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
eshop-order        5/5     5            5           46s
ubuntu@edu-k8s:~/$ kubectl get po
NAME                                READY   STATUS    RESTARTS   AGE
eshop-order-ff866c56b-8k8cq         1/1     Running   0          14s
eshop-order-ff866c56b-dcfr9         1/1     Running   0          14s
eshop-order-ff866c56b-fh644         1/1     Running   0          14s
eshop-order-ff866c56b-ltkg6         1/1     Running   0          58s
eshop-order-ff866c56b-q9gd2         1/1     Running   0          14s

2. Deployment 생성하고 Scaling 하기

Question : Create a deployment as follows.

TASK :

name : webserver

2 replicas

label : app_env_stage=dev

container name : webserver

container image : ghcr.io/shclub/nginx:1.14

Scale Out Deployment.

Scale the deployment webserver to 3 pods

아래 명령어를 실행하여 deployment 를 생성하고 label를 설정합니다.

ubuntu@edu-k8s:~/$ kubectl create deployment webserver --image=ghcr.io/shclub/nginx:1.14 --replicas=2

ubuntu@edu-k8s:~/$ kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
eshop-order        1/1     1            1           7s

결과값 : webserver 이름으로 deployment 생성 ( Replica : 2 )

ubuntu@edu-k8s:~/$ kubectl get deploy
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
webserver          2/2     2            2           5m29s

replicas 3 으로 증가.

ubuntu@edu-k8s:~/$ kubectl get po
NAME                                READY   STATUS    RESTARTS   AGE
webserver-5586594bbf-kqkfr          1/1     Running   0          3m47s
webserver-5586594bbf-td2z5          1/1     Running   0          3m47s
webserver-5586594bbf-vpf5j          1/1     Running   0          7s

7. Rolling Update

Question : Create a deployment as follows.

TASK :

name : nginx-app

Using container nginx with version : ghcr.io/shclub/nginx:1.14-alpine

The deployment should contain 3 replicas Next, deploy the application with new version ghcr.io/shclub/nginx:1.14.2-alpine, by performing a rolling update
Finally, rollback that update to the previous version ghcr.io/shclub/nginx:1.14-alpine

결과값 : deployment 와 rollout history를 확인 합니다.

ubuntu@edu-k8s:~/$ kubectl rollout  history deployment nginx-app
deployment.apps/nginx-app
REVISION  CHANGE-CAUSE
2         <none>
3         <none>

8. Node Selector

Question : Schedule a pod as follows.

TASK :

name : eshop-store

namespace : 본인 namespace

image : ghcr.io/shclub/nginx

Node Selector : disktype=ssd ( 특정 노드가 세팅 되어 있고 특정 노드에만 pod를 띄운다 )

결과값 : node의 label를 확인 하고 pod 생성.

아래 명령어로 node 에 label 설정함. ( 강사가 사전 설정하여 불필요 )

ubuntu@edu-k8s:~$ kubectl label nodes edu-k8s.worker01 disktype=ssd
node/edu-k8s.worker01 labeled

node별로 disktype label 확인.

ubuntu@edu-k8s:~$ kubectl get nodes -L disktype
NAME                      STATUS   ROLES                  AGE   VERSION    DISKTYPE
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready    <none>                 32d   v1.21.13   ssd
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13

pod가 특정 node에서 실행이 됨.

ubuntu@edu-k8s:~/teacher$ kubectl get po -o wide
NAME             READY   STATUS    RESTARTS   AGE   IP                NODE               NOMINATED NODE   READINESS GATES
eshop-store      1/1     Running   0          9s    192.168.10.5      edu-k8s.worker01   <none>           <none>

9. Node 관리

cordon : 해당 노드에 pod scheduling 불가.

ubuntu@edu-k8s:~$ kubectl get nodes
NAME                      STATUS   ROLES                  AGE   VERSION
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready    <none>                 32d   v1.21.13
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13
...
ubuntu@edu-k8s:~$ kubectl cordon edu-k8s.worker01
node/edu-k8s.worker01 cordoned
ubuntu@edu-k8s:~$ kubectl get nodes
NAME                      STATUS   ROLES                  AGE   VERSION
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready,SchedulingDisabled    <none>                 32d   v1.21.13
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13

uncordon : 해당 노드에 pod scheduling 가능.

drain : 해당 노드의 모든 pod를 다른 node로 보내고 현재 노드에 스케쥴링 하지 말아라

ubuntu@edu-k8s:~$ kubectl drain edu-k8s.worker01
node/edu-k8s.worker01 already cordoned
error: unable to drain node "edu-k8s.worker01" due to error:[cannot delete DaemonSet-managed Pods (use --ignore-daemonsets to ignore): calico-system/calico-node-pdvl9, calico-system/csi-node-driver-brjbc, kube-system/kube-proxy-ht2sb, cannot delete Pods declare no controller (use --force to override): devops/eshop-store, devops/web, devops/web2, devops/web4, edu1/eshop-main, edu3/eshop-main, edu4/eshop-main], continuing command...
There are pending nodes to be drained:
 node1
cannot delete DaemonSet-managed Pods (use --ignore-daemonsets to ignore): calico-system/calico-node-pdvl9, calico-system/csi-node-driver-brjbc, kube-system/kube-proxy-ht2sb
cannot delete Pods declare no controller (use --force to override): devops/eshop-store, devops/web, devops/web2, devops/web4, edu1/eshop-main, edu3/eshop-main, edu4/eshop-main

위에서 보면 정상적으로 되어 있지 않을것을 볼 수 있다. daemonset 은 죽이지 못해서 나는 에러이고 이것을 무시하는 명령어를 포함하여 다시 수행한다.

cannot delete DaemonSet-managed Pods (use --ignore-daemonsets to ignore)

ubuntu@edu-k8s:~$ kubectl drain edu-k8s.worker01 --ignore-daemonsets
node/edu-k8s.worker01 already cordoned
error: unable to drain node "edu-k8s.worker01" due to error:cannot delete Pods declare no controller (use --force to override): devops/eshop-store, devops/web, devops/web2, devops/web4, edu1/eshop-main, edu3/eshop-main, edu4/eshop-main, continuing command...
There are pending nodes to be drained:
 edu-k8s.worker01
cannot delete Pods declare no controller (use --force to override): devops/eshop-store, devops/web, devops/web2, devops/web4, edu1/eshop-main, edu3/eshop-main, edu4/eshop-main

추가적으로 강제 옵션을 주고 실행을 하면 정상적으로 수행이 된다.

ubuntu@edu-k8s:~$ kubectl drain edu-k8s.worker01 --ignore-daemonsets --force
error: unknown flag: --ignore-daemonsets
See 'kubectl drain --help' for usage
node/node1 already cordoned
Warning: ignoring DaemonSet-managed Pods: calico-system/calico-node-pdvl9, calico-system/csi-node-driver-brjbc, kube-system/kube-proxy-ht2sb; deleting Pods that declare no controller: devops/eshop-store, devops/web, devops/web2, devops/web4, edu1/eshop-main, edu3/eshop-main, edu4/eshop-main
evicting pod calico-system/calico-typha-c5f6b8544-vswc7
evicting pod edu4/eshop-main
evicting pod calico-apiserver/calico-apiserver-bf7fb56f6-nphl7
evicting pod devops/web
evicting pod devops/eshop-store
evicting pod devops/nginx-app-5d98f7444d-8k5p8
evicting pod devops/nginx-app-5d98f7444d-p5jwr
evicting pod devops/web4
evicting pod devops/web2
evicting pod edu1/eshop-main
evicting pod edu3/eshop-main
pod/calico-typha-c5f6b8544-vswc7 evicted
I1031 17:11:19.884568  836242 request.go:682] Waited for 1.007397548s due to client-side throttling, not priority and fairness, request: GET:https://192.168.0.150:6443/api/v1/namespaces/devops/pods/eshop-store
pod/eshop-store evicted
pod/web evicted
pod/eshop-main evicted
pod/nginx-app-5d98f7444d-p5jwr evicted
pod/web4 evicted
pod/calico-apiserver-bf7fb56f6-nphl7 evicted
pod/eshop-main evicted
pod/eshop-main evicted
pod/nginx-app-5d98f7444d-8k5p8 evicted
pod/web2 evicted
node/edu-k8s.worker01 drained

node를 조회해 본다.

ubuntu@edu-k8s:~$ kubectl get nodes
NAME                      STATUS   ROLES                  AGE   VERSION
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready,SchedulingDisabled    <none>                 32d   v1.21.13
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13

pod를 조회해 보면 모든 pod가 edu-k8s.worker02 에서 실행 되는것을 볼수 있다.

root@master:~# kubectl get po -o wide
NAME                         READY   STATUS    RESTARTS   AGE     IP               NODE    NOMINATED NODE   READINESS GATES
eshop-cart-app               2/2     Running   0          20m     192.168.104.16   edu-k8s.worker02   <none>           <none>
eshop-main                   1/1     Running   0          6d22h   192.168.104.7    edu-k8s.worker02   <none>           <none>
nginx-app-5d98f7444d-8g9tb   1/1     Running   0          5m51s   192.168.104.21   edu-k8s.worker02   <none>           <none>

다시 원복 하기 위해서는 uncordon 명령어를 사용한다.

ubuntu@edu-k8s:~/$ kubectl uncordon edu-k8s.worker01
node/edu-k8s.worker01 uncordoned
ubuntu@edu-k8s:~/$ kubectl get nodes
NAME                      STATUS   ROLES                  AGE   VERSION
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready    <none>                 32d   v1.21.13
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13

Question : Set the node named edu-k8s.worker01 as unavailable and reschedule all the pods running on it.

결과값 : drain 명령어 사용

ubuntu@edu-k8s:~/$ kubectl get nodes
NAME                      STATUS   ROLES                  AGE   VERSION
edu-k8s.dmz-infra01       Ready    <none>                 32d   v1.21.13
edu-k8s.master01          Ready    control-plane,master   32d   v1.21.13
edu-k8s.private-infra01   Ready    <none>                 32d   v1.21.13
edu-k8s.worker01          Ready,SchedulingDisabled    <none>                 32d   v1.21.13
edu-k8s.worker02          Ready    <none>                 32d   v1.21.13

10. Node 정보 수집

1. Check Ready Nodes

Question : Check to see how many nodes are ready ( not including nodes tainted NoSchedule) and write the number to ./RN0001.

결과값 : /RN0001 파일을 열어 본다. 2가 나와야 함.

ubuntu@edu-k8s:~/$ cat ./RN0001
2

2. Count the Number of Nodes That Are Ready to Run Normal Workloads

Question : Determine how many nodes in the cluster and ready to run normal workloads (i.e, workloads that do not have any special tolerations ).

Output this number to the file write the number to ./NODE-count.

결과값 : /NODE-count 파일을 열어 본다. 3이 나와야 함.

ubuntu@edu-k8s:~/$ cat ./NODE-count
3

11. Deployment & Expose the Service

Question : Reconfigure the existing deployment front-end and add a port specification named http exposing port 80/tcp of the existing container nginx.

Create a new service named front-end-svc exposing the container port http.

Configure the new service to also expose the individual Pods via a NodePort on the nodes on which they are scheduled.

먼저 아래 yaml 화일을 deployment를 생성해 놓는다.

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: front-end
  name: front-end
spec:
  replicas: 2
  selector:
    matchLabels:
      app: front-end
  template:
    metadata:
      labels:
        app: front-end
    spec:
      containers:
      - image: ghcr.io/shclub/nginx
        name: nginx

deployment 가 실행되어 있는 것을 확인한다.

ubuntu@edu-k8s:~/$ kubectl get deploy
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
front-end          2/2     2            2           8s

결과값 : svc를 조회 해 보고 서비스 이름과 NodePort가 생성되어 있는지 확인.

service를 조회 해 보면 NodePort가 생성된 것을 확인 할 수있다.

ubuntu@edu-k8s:~/$ kubectl get svc
NAME                        TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
front-end-svc               NodePort    172.30.145.50    <none>        80:32495/TCP     2m41s```

curl 명령어로 해당 서비스를 호출해 본다.

아래와 같이 niginx 첫 화면 내용이 나오면 성공.

ubuntu@edu-k8s:~/$ curl 211.34.231.91:32495
<!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>

12. Pod log 추출

Pod Log를 stand out 으로 추출.

Question : Monitor the logs of pod custom-app and Extract log lines corresponding to error file not found. Write them to ./podlog.

14. init 컨테이너를 포함한 Pod 운영

init 컨테이너는 main container 가 동작 되기전에 실행되는 컨테이너

주로 환경 구성 . DB 인 경우는 초기 DB Script

init 컨테이너는 항상 완료가 되어야 한다.

참고 : https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

Question : Perform the following.

TASK :
Add an init container to web-pod(which has been defined in spec file ./webpod.yaml).
The init container should create an empty file named /home/data.txt.
if /home/data.txt is not detected. the Pod should exit.
Once the spec file has been updated with the init container definition. the pod should be created.

web-pod.yaml 화일

apiVersion: v1
kind: Pod
metadata:
  name: web-pod
spec:
  containers:
  - image: ghcr.io/shclub/busybox:1.28
    name: main
    command: ['sh','-c','if [ !-f /home/data.txt ];then exit 1;else sleep 300;fi']
    volumeMounts:
    - name: workdir
      mountPath: "/home"
  volumes:
  - name: workdir
    emptyDir: {}

결과값 : web-pod 이름의 pod에서 /home 폴더에 data.txt 화일이 있어야 함.

아래 명령어 사용

ubuntu@edu-k8s:~/$ kubectl exec -it web-pod sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
/ # ls
bin   dev   etc   home  proc  root  run   sys   tmp   usr   var
/ # cd home
/home # ls
data.txt

15. NodePort 서비스 생성

Question : Create the service as type NodePort with port 32767 for the nginx pod with pod selector app: webui

nginx.yaml 화일

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: webui
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webui
  strategy: {}
  template:
    metadata:
      labels:
        app: webui
    spec:
      containers:
      - image: ghcr.io/shclub/nginx
        name: nginx

결과값 : 서비스를 조회 하여 해당 서비스가 NodePort 로 설정 되어 있는지 확인한다.

서비스를 조회한다.

ubuntu@edu-k8s:~/$ kubectl get svc  
nginx                       NodePort    172.30.228.71    <none>        80:32767/TCP     16s

curl 명령어로 서비스를 호출한다.

ubuntu@edu-k8s:~/$ curl 211.34.231.84:32767
<!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>

16. ConfigMap 운영

configMap을 환경 변수로 전달하는 방법과 volume mount를 해서 전달하는 방법 2가지를 다 공부해야 한다.

https://kubernetes.io/docs/concepts/configuration/configmap/

Question : Expose Configuration settings

TASK :
All operations in this question should be performed in the < your namespace > Create ConfigMap called web-config that contains the following two entries

connection_string=localhost:80

external_url=cncf.io

Run a pod called web-pod with a single container running the nginx:1.19.8-alpine image, and expose these configuration settings as environment variables inside the container.

결과값 : pod 안에 환경 변수 2개가 들어 있는지 확인한다.

해당 POD의 환경 변수를 확인한다.

ubuntu@edu-k8s:~/$ kubectl exec  web-pod -- env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
TERM=xterm
HOSTNAME=web-pod
connection_string=localhost:80
external_url=cncf.io

17. Secret 운영

Secret 은 configMap과 비슷하지만 base64로 인코딩 하는 부분만 다름.

https://kubernetes.io/docs/concepts/configuration/secret/

Secret는 용도에 따라서 3가지가 있고 우리는 일반 적인 방식인 Generic으로 진행을 합니다.

ubuntu@edu-k8s:~/$ kubectl create secret --help
Create a secret using specified subcommand.

Available Commands:
  docker-registry Create a secret for use with a Docker registry
  generic         Create a secret from a local file, directory or literal value
  tls             Create a TLS secret

Usage:
  kubectl create secret [flags] [options]

Use "kubectl <command> --help" for more information about a given command.

Secret을 생성 후 Pod에 전달

Question : Create a Kubernetes secret and expose using a file in the pod.

TASK :
Create a Kubernetes Secret as follows.

Name : super-secret

DATA : password=secretpass

Create a Pod named pod-secrets-via-file, using the redis image, which mounts a secret named super-secret at /secrets.

Create a second Pod named pod-secrets-via-env, using the redis image, which exports password as PASSWORD.

결과값 :

file 로 pod에 받기

/secrets 폴더에 해당 화일이 있는지 확인한다.

ubuntu@edu-k8s:~/$ kubectl exec -it pod-secrets-via-file -- ls /secrets
password

환경변수로 받기

pod에서 env로 확인한다.

ubuntu@edu-k8s:~/$ kubectl exec -it pod-secrets-via-env -- env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
TERM=xterm
HOSTNAME=pod-secrets-via-env
NSS_SDB_USE_CACHE=no
PASSWORD=secretpass

19. Persistent Volume

Question : Create Persistent Volume

TASK :
Create a persistent volume whith name app-config of capacity 1Gi and access mode ReadWriteMany. StorageClass: az-c The Type of volume is hostPath and its location is /root/cka_pvc_test.

root폴더에서 아래 폴더를 생성한다.

ubuntu@edu-k8s:~/$ mkdir -p cka_pvc_test

결과값

ubuntu@edu-k8s:~/$ kubectl get pv app-config
NAME         CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
app-config   1Gi        RWX            Recycle          Available           az-c                    10s

20. Persistent Volume Claim 을 사용하는 POD 운영 ( 자주나옴 )

Question : Application with PersistentVolumeClaim

TASK 1 :
Create a new PersistentVolumeClaim

Name : app-volume

StorageClass : az-c

Capacity : 10Mi

TASK 2 :
Create a new Pod which mounts the PersistentVolumeClaim as a volume

Name : web-server-pod

Image : nginx

Mount path : /usr/share/nginx/html

TASK 3 :
Configure the new Pod to have ReadWriteMany access on the volume.

참고 : https://kubernetes.io/docs/tasks/configure-pod-container/configure-persistent-volume-storage/

결과값

ubuntu@edu-k8s:~/$ kubectl get po web-server-pod
NAME             READY   STATUS    RESTARTS   AGE
web-server-pod   1/1     Running   0          8s

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cka.md

cka.md

CKA 문제

1. ETCD Backup & Restore

2. pod 생성하기

3. Static POD 생성하기

4. Multi Container POD 생성하기

5. Side-car container POD 실행

6. Deployment & Pod Scale

1. Pod scale out

2. Deployment 생성하고 Scaling 하기

7. Rolling Update

8. Node Selector

9. Node 관리

10. Node 정보 수집

1. Check Ready Nodes

2. Count the Number of Nodes That Are Ready to Run Normal Workloads

11. Deployment & Expose the Service

12. Pod log 추출

14. init 컨테이너를 포함한 Pod 운영

15. NodePort 서비스 생성

16. ConfigMap 운영

17. Secret 운영

19. Persistent Volume

20. Persistent Volume Claim 을 사용하는 POD 운영 ( 자주나옴 )

Files

cka.md

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cka.md

File metadata and controls

CKA 문제

1. ETCD Backup & Restore

2. pod 생성하기

3. Static POD 생성하기

4. Multi Container POD 생성하기

5. Side-car container POD 실행

6. Deployment & Pod Scale

1. Pod scale out

2. Deployment 생성하고 Scaling 하기

7. Rolling Update

8. Node Selector

9. Node 관리

10. Node 정보 수집

1. Check Ready Nodes

2. Count the Number of Nodes That Are Ready to Run Normal Workloads

11. Deployment & Expose the Service

12. Pod log 추출

14. init 컨테이너를 포함한 Pod 운영

15. NodePort 서비스 생성

16. ConfigMap 운영

17. Secret 운영

19. Persistent Volume

20. Persistent Volume Claim 을 사용하는 POD 운영 ( 자주나옴 )