[Kubernetes] Kubernetes Pod | init container

3. init container를 적용한 Pod

1. init container 

• 앱 컨테이너 실행 전에 미리 동작시킬 컨테이너 
• 본 Container가 실행되기 전에 사전 작업이 필요할 경우 사용 
• 초기화 컨테이너가 모두 실행된 후에 앱 컨테이너를 실행 
• https://kubernetes.io/ko/docs/concepts/workloads/pods/init-containers/
• 위 문서의 example을 사용하여 init container를 생성할 수 있다.  

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: busybox:1.28
    command: ['sh', '-c', 'echo The app is running! && sleep 3600']
  initContainers:
  - name: init-myservice
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup myservice.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for myservice; sleep 2; done"]
  - name: init-mydb
    image: busybox:1.28
    command: ['sh', '-c', "until nslookup mydb.$(cat /var/run/secrets/kubernetes.io/serviceaccount/namespace).svc.cluster.local; do echo waiting for mydb; sleep 2; done"]

 

2. infra container(pause) 

• pod의 환경을 만들어주는 컨테이너
• 파드를 생성했을 때 자동으로 생성됨

controlplane $ docker ps
CONTAINER ID        IMAGE                  COMMAND                  CREATED             STATUS              PORTS               NAMES
fcb01ebcacc3        67da37a9a360           "/coredns -conf /etc…"   3 seconds ago       Up 2 seconds                            k8s_coredns_coredns-66bff467f8-8smxh_kube-system_7faf42b3-65cc-4a8a-a388-8992ef4e3e34_0
5fd877af3f78        k8s.gcr.io/pause:3.2   "/pause"                 4 seconds ago       Up 3 seconds                            k8s_POD_coredns-66bff467f8-8smxh_kube-system_7faf42b3-65cc-4a8a-a388-8992ef4e3e34_0
c2e2e253eef2        4e9f801d2217           "/opt/bin/flanneld -…"   10 seconds ago      Up 9 seconds                            k8s_kube-flannel_kube-flannel-ds-amd64-6bc8d_kube-system_876910e6-6dd6-41aa-80f7-5941f7491ad8_0
b51633284dca        43940c34f24f           "/usr/local/bin/kube…"   14 seconds ago      Up 13 seconds                           k8s_kube-proxy_kube-proxy-4n57r_kube-system_9f3492b9-0c5d-415f-8e35-4eb12f4a3546_0
ef559a607e61        k8s.gcr.io/pause:3.2   "/pause"                 15 seconds ago      Up 14 seconds                           k8s_POD_kube-flannel-ds-amd64-6bc8d_kube-system_876910e6-6dd6-41aa-80f7-5941f7491ad8_0

➜ webserver 파드를 실행했을 때 컨테이너 상태 

 

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Reference

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