从节点映像运行docker容器时找不到Npm

# Dockerfile
FROM node:7-alpine
RUN mkdir -p /src/app
WORKDIR /src/app
COPY package.json /src/app/package.json
RUN npm install
COPY . /src/app
EXPOSE 3000
CMD ['npm', 'start']
# Dockerfile
FROM node:7-alpine
RUN mkdir -p /s