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이 포스팅은 아래의 유튜브 채널 "따배"를 따라서 학습한 내용입니다.
[관련 이론]
Pod 생성 과정
1. 사용자가 pod 생성 요청을 보낸다. 이 요청은 kube-apiserver로 전달된다.
2. kube-apiserver는 새로운 pod의 정보를 etcd에 저장한다.
3. kube-scheduler는 etcd의 정보를 참조하여 scheduler 정책에 따라 pod가 생성될 node를 결정한다.
4. 선택된 노드의 kubelet은 etcd에서 할당된 Pod 정보를 조회하고, 컨테이너 런타임(Container Runtime)을 사용하여 Pod을 실행한다.
5. kube-proxy는 서비스(Service)와 Pod 간 네트워크 라우팅을 설정한다.
✅ 전체 Pod 생성 흐름 요약
1️⃣ 사용자 → kubectl apply -f pod.yaml 실행
2️⃣ kube-apiserver → 요청 검증 후 etcd에 저장
3️⃣ kube-scheduler → 적절한 노드 선택
4️⃣ kubelet → 컨테이너 이미지 다운로드(containerd repository) & Pod 실행
5️⃣ kube-proxy → 네트워크 설정
6️⃣ Pod가 Running 상태로 전환됨
[Precondition]
(1) 테스트 환경
(1.1) Rocky Linux Cluster
: 직접 구성
[root@k8s-master ~]# k get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master Ready control-plane 30d v1.27.2 192.168.56.30 <none> Rocky Linux 8.10 (Green Obsidian) 4.18.0-553.33.1.el8_10.x86_64 containerd://1.6.32
k8s-node1 Ready <none> 30d v1.27.2 192.168.56.31 <none> Rocky Linux 8.8 (Green Obsidian) 4.18.0-477.10.1.el8_8.x86_64 containerd://1.6.21
k8s-node2 Ready <none> 30d v1.27.2 192.168.56.32 <none> Rocky Linux 8.8 (Green Obsidian) 4.18.0-477.10.1.el8_8.x86_64 containerd://1.6.21
[root@k8s-master ~]#
(1.2) Ubuntu Cluster
: kodekloud 테스트 환경 활용
controlplane ~ ➜ kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
controlplane Ready control-plane 9m6s v1.31.0 192.6.94.6 <none> Ubuntu 22.04.4 LTS 5.4.0-1106-gcp containerd://1.6.26
node01 Ready <none> 8m31s v1.31.0 192.6.94.9 <none> Ubuntu 22.04.4 LTS 5.4.0-1106-gcp containerd://1.6.26
https://learn.kodekloud.com/user/courses/udemy-labs-certified-kubernetes-administrator-with-practice-tests
(2) 사전 필요 설정
: 문제 풀이에 사용할 namespace 생성
controlplane ~ ➜ k create namespace ecommerce
namespace/ecommerce created
controlplane ~ ➜ k get namespaces
NAME STATUS AGE
default Active 18m
ecommerce Active 10s
kube-node-lease Active 18m
kube-public Active 18m
kube-system Active 18m
: 문제에서 제시하는 "k8s" context를 생성하고 적용
controlplane ~ ➜ k config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
* kubernetes-admin@kubernetes kubernetes kubernetes-admin
controlplane ~ ➜ k config set-context k8s --cluster=kubernetes --user=kubernetes-admin
Context "k8s" created.
controlplane ~ ➜ k config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
k8s kubernetes kubernetes-admin
* kubernetes-admin@kubernetes kubernetes kubernetes-admin
controlplane ~ ➜ k config use-context k8s
Switched to context "k8s".
controlplane ~ ➜ k config get-contexts
CURRENT NAME CLUSTER AUTHINFO NAMESPACE
* k8s kubernetes kubernetes-admin
kubernetes-admin@kubernetes kubernetes kubernetes-admin
[Question]
Create a new namespace and create a pod in the namespace
cluster: k8s
namespace name: ecommerce
pod Name: eshop-main
image: nginx:1.17
env: DB=mysql
[Solve]
(1) pod 생성 옵션 확인
: k run --help로 pod 생성 옵션 확인
(2) pod 생성
: dry-run으로 pod 생성 설정에 이상이 없는지 생성 전에 확인 후 pod 생성
controlplane ~ ➜ kubectl run eshop-main --image=nginx:1.17 --env="DB=mysql" --namespace=ecommerce --dry-run=client -o yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: eshop-main
name: eshop-main
namespace: ecommerce
spec:
containers:
- env:
- name: DB
value: mysql
image: nginx:1.17
name: eshop-main
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}
controlplane ~ ➜ kubectl run eshop-main --image=nginx:1.17 --env="DB=mysql" --namespace=ecommerce
pod/eshop-main created
(3) 생성한 pod 확인
controlplane ~ ➜ kubectl get pods -n ecommerce
NAME READY STATUS RESTARTS AGE
eshop-main 1/1 Running 0 21s
controlplane ~ ➜ kubectl describe pods -n ecommerce eshop-main
Name: eshop-main
Namespace: ecommerce
Priority: 0
Service Account: default
Node: node01/192.168.63.141
Start Time: Wed, 29 Jan 2025 11:28:49 +0000
Labels: run=eshop-main
Annotations: cni.projectcalico.org/containerID: 11ef1a1332de00fca960c7fe0b1016374f8cba0e9c3211640862f312309656ca
cni.projectcalico.org/podIP: 172.17.1.2/32
cni.projectcalico.org/podIPs: 172.17.1.2/32
Status: Running
IP: 172.17.1.2
IPs:
IP: 172.17.1.2
Containers:
eshop-main:
Container ID: containerd://a2794196facfb452d8ad7b9740071f52c169a4003035f5d3d7029506139337ea
Image: nginx:1.17
Image ID: docker.io/library/nginx@sha256:6fff55753e3b34e36e24e37039ee9eae1fe38a6420d8ae16ef37c92d1eb26699
Port: <none>
Host Port: <none>
State: Running
Started: Wed, 29 Jan 2025 11:28:53 +0000
Ready: True
Restart Count: 0
Environment:
DB: mysql
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-t4kd9 (ro)
Conditions:
Type Status
PodReadyToStartContainers True
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
kube-api-access-t4kd9:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
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 40s default-scheduler Successfully assigned ecommerce/eshop-main to node01
Normal Pulling 39s kubelet Pulling image "nginx:1.17"
Normal Pulled 36s kubelet Successfully pulled image "nginx:1.17" in 2.862s (2.862s including waiting). Image size: 51030575 bytes.
Normal Created 36s kubelet Created container eshop-main
Normal Started 36s kubelet Started container eshop-main
controlplane ~ ➜
[사용 커맨드 정리]
k config use-context k8s
kubectl run eshop-main --image=nginx:1.17 --env="DB=mysql" --namespace=ecommerce --dry-run=client -o yaml
kubectl run eshop-main --image=nginx:1.17 --env="DB=mysql" --namespace=ecommerce
kubectl get pods -n ecommerce
kubectl describe pods -n ecommerce eshop-main
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