클라우드/Kubernetes(쿠버네티스)

[쿠버네티스] kubectl & Pods

happyso 2020. 9. 21. 00:53

쿠버네티스 실습 환경 설정

기본에 사용하던 가상머진 모두 중지

#1 가상머신 생성

C:\kubernetes\Vagrantfile

# -*- mode: ruby -*-

# vi: set ft=ruby :

Vagrant.configure("2") do |config|

config.vm.box = "ubuntu/bionic64"

config.vm.hostname = "ubuntu"

config.vm.network "private_network", ip: "192.168.111.110"

config.vm.synced_folder ".", "/home/vagrant/sync", disabled: true

config.vm.provider "virtualbox" do |vb|

vb.cpus = 2

vb.memory = 2048

end

C:\kubernetes> vagrant up

C:\kubernetes> vagrant ssh

#2 패키지 최신화

vagrant@ubuntu:~$ sudo su

root@ubuntu:/home/vagrant# cd

root@ubuntu:~# apt update

root@ubuntu:~# apt upgrade

#3 도커 설치 및 설정

root@ubuntu:~# apt install docker.io -y

root@ubuntu:~# usermod -a -G docker vagrant

root@ubuntu:~# service docker restart

root@ubuntu:~# chmod 666 /var/run/docker.sock

root@ubuntu:~# docker version

Client:

Version: 19.03.6

API version: 1.40

Go version: go1.12.17

Git commit: 369ce74a3c

Built: Fri Feb 28 23:45:43 2020

OS/Arch: linux/amd64

Experimental: false

Server:

Engine:

Version: 19.03.6

API version: 1.40 (minimum version 1.12)

Go version: go1.12.17

Git commit: 369ce74a3c

Built: Wed Feb 19 01:06:16 2020

OS/Arch: linux/amd64

Experimental: false

containerd:

Version: 1.3.3-0ubuntu1~18.04.2

GitCommit:

runc:

Version: spec: 1.0.1-dev

GitCommit:

docker-init:

Version: 0.18.0

GitCommit:

#4 kubectl 설치

https://kubernetes.io/ko/docs/tasks/tools/install-kubectl/

root@ubuntu:~# apt-get update && sudo apt-get install -y apt-transport-https gnupg2

root@ubuntu:~# curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

root@ubuntu:~# echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee -a /etc/apt/sources.list.d/kubernetes.list

root@ubuntu:~# apt-get update

root@ubuntu:~# apt-get install -y kubectl

root@ubuntu:~# kubectl version

Client Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.2", GitCommit:"f5743093fd1c663cb0cbc89748f730662345d44d", GitTreeState:"clean", BuildDate:"2020-09-16T13:41:02Z", GoVersion:"go1.15", Compiler:"gc", Platform:"linux/amd64"}

The connection to the server localhost:8080 was refused - did you specify the right host or port?

#5 Minikube 설치

https://kubernetes.io/ko/docs/tasks/tools/install-minikube/

root@ubuntu:~# curl -Lo minikube https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64 && chmod +x minikube

% Total % Received % Xferd Average Speed Time Time Time Current

Dload Upload Total Spent Left Speed

100 55.8M 100 55.8M 0 0 60.2M 0 --:--:-- --:--:-- --:--:-- 60.1M

root@ubuntu:~# mkdir -p /usr/local/bin/

root@ubuntu:~# install minikube /usr/local/bin/

k8s = kubernetes

#6 클러스터 시작

root@ubuntu:~# exit

exit

vagrant@ubuntu:~$ minikube start

😄 minikube v1.13.0 on Ubuntu 18.04 (vbox/amd64)

✨ Automatically selected the docker driver

⛔ Requested memory allocation (1992MB) is less than the recommended minimum 2000MB. Deployments may fail.

🧯 The requested memory allocation of 1992MiB does not leave room for system overhead (total system memory: 1992MiB). You may face stability issues.

💡 Suggestion: Start minikube with less memory allocated: 'minikube start --memory=1992mb'

👍 Starting control plane node minikube in cluster minikube

🚜 Pulling base image ...

💾 Downloading Kubernetes v1.19.0 preload ...

> preloaded-images-k8s-v6-v1.19.0-docker-overlay2-amd64.tar.lz4: 486.28 MiB

🔥 Creating docker container (CPUs=2, Memory=1992MB) ...

🐳 Preparing Kubernetes v1.19.0 on Docker 19.03.8 ...

🔎 Verifying Kubernetes components...

🌟 Enabled addons: default-storageclass, storage-provisioner

🏄 Done! kubectl is now configured to use "minikube" by default

vagrant@ubuntu:~$ minikube status

minikube

type: Control Plane

host: Running

kubelet: Running

apiserver: Running

kubeconfig: Configured

vagrant@ubuntu:~$ kubectl version

Server Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.0", GitCommit:"e19964183377d0ec2052d1f1fa930c4d7575bd50", GitTreeState:"clean", BuildDate:"2020-08-26T14:23:04Z", GoVersion:"go1.15", Compiler:"gc", Platform:"linux/amd64"}

vagrant@ubuntu:~$ kubectl version --short

Client Version: v1.19.2

Server Version: v1.19.0

중지 ⇒ minikube stop

삭제 ⇒ minikube delete

쿠버네티스

https://myanjini.tistory.com/entry/o2-Kubernetes

포드(pod)

컨테이너 애플리케이션의 기본 단위

1개 이상의 컨테이너로 구성된 컨테이너의 집합

여러 개의 컨테이너를 추상화해서 하나의 애플리케이션으로 동작하도록 묶어 놓은 컨테이너의 묶음

nginx 컨테이너로 구성된 포드를 생성

vagrant@ubuntu:~/kub01$ vi nginx-pod.yml

apiVersion: v1 ⇐ YAML 파일에서 정의한 오브젝트의 API 버전

kind: Pod ⇐ 리소스의 종류 (kubectl api-resources 명령의 KIND 항목)

metadata: ⇐ 라벨, 주석, 이름과 같은 리소스의 부가 정보

spec:

containers: ⇐ 리소스 생성을 위한 정보

- name: my-nginx-container

image: nginx:latest

ports:

- containerPort: 80

protocol: TCP

새로운 파드 생성 및 확인

vagrant@ubuntu:~/kub01$ kubectl apply -f nginx-pod.yml

pod/my-nginx-pod created

vagrant@ubuntu:~/kub01$ kubectl get pods

NAME READY STATUS RESTARTS AGE

my-nginx-pod 1/1 Running 0 35s

vagrant@ubuntu:~/kub01$ kubectl get po ⇐ pods의 축약어(po)를 이용할 수 있음

NAME READY STATUS RESTARTS AGE

my-nginx-pod 1/1 Running 0 52s

생성된 리소스의 자세한 정보를 확인

vagrant@ubuntu:~/kub01$ kubectl describe pods my-nginx-pod

Name: my-nginx-pod

Namespace: default

Priority: 0

Node: minikube/172.17.0.2

Start Time: Fri, 18 Sep 2020 06:35:11 +0000

Labels: <none>

Annotations: <none>

Status: Running

IP: 172.18.0.3

IPs:

IP: 172.18.0.3

Containers:

my-nginx-container:

Container ID: docker://6d35592cf4cf94fb0f45f90b85a7146516fa856d0ae583c0d6eded380f3e27d6

Image: nginx:latest

Image ID: docker-pullable://nginx@sha256:c628b67d21744fce822d22fdcc0389f6bd763daac23a6b77147d0712ea7102d0

Port: 80/TCP

Host Port: 0/TCP

State: Running

Started: Fri, 18 Sep 2020 06:35:20 +0000

Ready: True

Restart Count: 0

Environment: <none>

Mounts:

/var/run/secrets/kubernetes.io/serviceaccount from default-token-sh8hv (ro)

Conditions:

Type Status

Initialized True

Ready True

ContainersReady True

PodScheduled True

Volumes:

default-token-sh8hv:

Type: Secret (a volume populated by a Secret)

SecretName: default-token-sh8hv

Optional: false

QoS Class: BestEffort

Node-Selectors: <none>

Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s

node.kubernetes.io/unreachable:NoExecute op=Exists for 300s

Events:

Type Reason Age From Message

---- ------ ---- ---- -------

Normal Scheduled 2m8s default-scheduler Successfully assigned default/my-nginx-pod to minikube

Normal Pulling 2m7s kubelet Pulling image "nginx:latest"

Normal Pulled 119s kubelet Successfully pulled image "nginx:latest" in 8.202726173s

Normal Created 119s kubelet Created container my-nginx-container

Normal Started 119s kubelet Started container my-nginx-container

클러스터 내부에 테스트를 위한 임시 포드를 생성해서 nginx 포드의 동작을 확인

### alicek106/ubuntu:curl 이미지를 이용해서 debug 이름의 포드를 생성

vagrant@ubuntu:~/kub01$ kubectl run -it --rm debug --image=alicek106/ubuntu:curl --restart=Never bash

If you don't see a command prompt, try pressing enter.

root@debug:/#

### debug 포드가 생성(실행)된 상태에서 포드를 조회

vagrant@ubuntu:~$ kubectl get pods

NAME READY STATUS RESTARTS AGE

debug 1/1 Running 0 58s

my-nginx-pod 1/1 Running 0 8m13s

### debug 포드에서 my-nginx-pod(172.18.0.3)로 요청을 전달

root@debug:/# curl 172.18.0.3

<!DOCTYPE html>

<html>

<head>

<title>Welcome to nginx!</title>

<style>

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

nginx.org.

Commercial support is available at

nginx.com.

<p><em>Thank you for using nginx.</em></p>

</body>

</html>

### debug 포드를 빠져 나오는 것과 동시에 삭제되는 것을 확인

root@debug:/# exit

exit

pod "debug" deleted

vagrant@ubuntu:~/kub01$ kubectl get pods

NAME READY STATUS RESTARTS AGE

my-nginx-pod 1/1 Running 0 12m

kubectl exec 명령으로 포드의 컨테이너에 명령어를 전달

vagrant@ubuntu:~/kub01$ kubectl exec -it my-nginx-pod -- bash

root@my-nginx-pod:/# ls /etc/nginx/

conf.d fastcgi_params koi-utf koi-win mime.types modules nginx.conf scgi_params uwsgi_params win-utf

root@my-nginx-pod:/# exit

exit

vagrant@ubuntu:~/kub01$

kubectl logs 명령으로 포드의 로그를 확인

vagrant@ubuntu:~/kub01$ kubectl logs my-nginx-pod

/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration ⇐ nginx 포드의 표준 출력 로그

/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/

/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh

10-listen-on-ipv6-by-default.sh: Getting the checksum of /etc/nginx/conf.d/default.conf

10-listen-on-ipv6-by-default.sh: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf

/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh

/docker-entrypoint.sh: Configuration complete; ready for start up

172.18.0.4 - - [18/Sep/2020:06:45:49 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.35.0" "-"

쿠버네티스 오브젝트를 삭제

vagrant@ubuntu:~/kub01$ kubectl delete -f nginx-pod.yml

pod "my-nginx-pod" deleted

vagrant@ubuntu:~/kub01$ kubectl get pods

No resources found in default namespace.

pod 정의

vagrant@ubuntu:~/kub01$ vi nginx-pod-with-ubuntu.yml

apiVersion: v1

kind: Pod

metadata:

spec:

containers:

- name: my-nginx-container

image: nginx:latest

ports:

- containerPort: 80

protocol: TCP

- name: ubuntu-sidecar-container

image: alicek106/rr-test:curl

command: [ "tail" ]

args: [ "-f", "/dev/null" ]

pod 생성

vagrant@ubuntu:~/kub01$ kubectl apply -f nginx-pod-with-ubuntu.yml

pod/my-nginx-pod created

vagrant@ubuntu:~/kub01$ kubectl get pods

NAME READY STATUS RESTARTS AGE

my-nginx-pod 0/2 ContainerCreating 0 11s

vagrant@ubuntu:~/kub01$ kubectl get pods

NAME READY STATUS RESTARTS AGE

my-nginx-pod 2/2 Running 0 21s

my-nginx-pod에는 my-nginx-container 컨테이너와 ubuntu-sidecar-container 컨테이너가 실행 중

### pod로 명령어를 전달할 때 실행할 컨테이너를 지정하면 default로 설정된 컨테이너가 실행

vagrant@ubuntu:~/kub01$ kubectl exec -it my-nginx-pod -- bash

Defaulting container name to my-nginx-container.

Use 'kubectl describe pod/my-nginx-pod -n default' to see all of the containers in this pod.

root@my-nginx-pod:/# exit

exit

### 특정 컨테이너에게 명령어를 전달할 때는 -c 옵션을 사용

vagrant@ubuntu:~/kub01$ kubectl exec -it my-nginx-pod -c ubuntu-sidecar-container -- bash

root@my-nginx-pod:/#

root@my-nginx-pod:/# curl localhost ⇒ 우분투 컨테이너 내부에서 localhost 요청에 대해 응답이 도착하는 것을 확인

<!DOCTYPE html> 우분투 컨테이너의 localhost에서 nginx 서버로 접근이 가능

<html> 포드 내부의 컨테이너들은 네트워크와 같은 리눅스 네임스페이스를 공유

<head>

<title>Welcome to nginx!</title>

<style>

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

nginx.org.

Commercial support is available at

nginx.com.

<p><em>Thank you for using nginx.</em></p>

</body>

</html>

### ubunut-sidecar-container 컨테이너만으로 구성된 pod를 생성한 후 해당 pod에서 curl을 동작

vagrant@ubuntu:~/kub01$ cp nginx-pod-with-ubuntu.yml nginx-pod-test.yml

vagrant@ubuntu:~/kub01$ vi nginx-pod-test.yml

apiVersion: v1

kind: Pod

metadata:

spec:

containers:

- name: ubuntu-sidecar-container

image: alicek106/rr-test:curl ⇐ 웹 서버를 포함하고 있지 않음

command: [ "tail" ]

args: [ "-f", "/dev/null" ]

vagrant@ubuntu:~/kub01$ kubectl apply -f nginx-pod-test.yml

pod/my-nginx-pod-test created

vagrant@ubuntu:~/kub01$ kubectl exec -it my-nginx-pod-test -- bash

root@my-nginx-pod-test:/# curl localhost

curl: (7) Failed to connect to localhost port 80: Connection refused ⇐ 80 포트로 서비스를 제공하고 있지 않다