How to run a script at the beginning of a container in Cloud Containers containers with quaternets

Question

I am trying to run a shell script at the beginning of a docker container running in Google Cloud Containers using Kubernetes. The structure of my application directory looks something like this. I would like to run the prod_start.sh script at the beginning of the container (although I do not want to include it in the Dockerfile). The current setup cannot start the container using Command not found file ./prod_start.sh does not exist. Any idea how to fix this?

app/
  ...
  Dockerfile
  prod_start.sh
  web-controller.yaml
  Gemfile
  ...

Dockerfile

FROM ruby
RUN mkdir /backend
WORKDIR /backend
ADD Gemfile /backend/Gemfile
ADD Gemfile.lock /backend/Gemfile.lock
RUN bundle install

web controller.yaml

apiVersion: v1
kind: ReplicationController
metadata:
  name: backend
  labels:
    app: myapp
    tier: backend
spec:
  replicas: 1
  selector:
    app: myapp
    tier: backend
  template:
    metadata:
      labels:
        app: myapp
        tier: backend
    spec:
      volumes:
      - name: secrets
        secret:
          secretName: secrets
      containers:
      - name: my-backend
        command: ['./prod_start.sh']
        image: gcr.io/myapp-id/myapp-backend:v1
        volumeMounts:
        - name: secrets
          mountPath: /etc/secrets
          readOnly: true
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
        ports:
        - containerPort: 80
          name: http-server

Answer 1

After many experiments, I find adding a script to Dockerfile:

ADD prod_start.sh /backend/prod_start.sh

, , yaml:

command: ['/bin/sh', './prod_start.sh']

.