How to keep node_modules inside container while using docker-compose and a non-root user?

Question

I'm looking for a way to achieve these goals at the same time:

• using a non-root user inside the container
• keeping node_modules inside container (to not to "pollute" the working directory on the host)
• not using a Dockerfile

I'm not sure if these goals are considered "best practice". For example, keeping node_modules inside the container has its disadvantages.

Currently my compose file is like this:

services:
  # ...

  node:
    image: "node:9"
    user: "node"
    working_dir: /home/node/app
    environment:
      # - NODE_ENV=production
      - NPM_CONFIG_PREFIX=/home/node/.npm-global
      - PATH=$PATH:/home/node/.npm-global/bin
    volumes:
      - ./proj/:/home/node/app
      - /home/node/app/node_modules # mark1
    ports:
      - "3001:3001"
    command: >
      bash -c "echo hello
      && ls -lh /home/node/app/ 
      && npm install
      && npm i -g babel-cli
      && npm i -g flow-bin
      && npm start"
    depends_on:
      - redis

but there's

"Error: EACCES: permission denied, access '/home/node/app/node_modules'".

If I comment out the #mark1 line, the container runs, however node_modules will be written onto the host (since ./proj is mounted)

I have read these two articles on the topic:

• https://blog.getjaco.com/jaco-labs-nodejs-docker-missing-manual/
• http://jdlm.info/articles/2016/03/06/lessons-building-node-app-docker.html

but neither meets my goal.

Update:

I added a line of ls -lh /home/node/app/ and found node_modules is owned by root. This could be the problem.

Answer 1

I ended up using a Dockerfile. It's minimum. (I keep some commented out lines for anyone may find them useful.)

We need to change the owner of node_modules inside the container. It seems the node:9 image doesn't require this. So this is only for node:9-alpine. (update: Sorry. I forgot to remove the built container with docker system prune. Both images need this. Here is a discussion on permissions/ownership of named volumes`)

FROM node:9-alpine

#ENV NPM_CONFIG_PREFIX=/home/node/.npm-global
#ENV PATH=$PATH:/home/node/.npm-global/bin

RUN mkdir -p /home/node/app/node_modules
RUN chown -R node:node /home/node/app

#USER node

#WORKDIR /home/node/app

#RUN npm install --silent --progress=false ; \
#    npm i -g babel-cli --silent --progress=false ;\
#    npm i -g flow-bin --silent --progress=false

The docker-compose.yml ended up being like:

services:
  # ...
  node:
    # image: "node:9-alpine"
    build: ./proj
    user: "node"
    working_dir: /home/node/app
    environment:
      # - NODE_ENV=production
      - NPM_CONFIG_PREFIX=/home/node/.npm-global
      - PATH=$PATH:/home/node/.npm-global/bin
    volumes:
      - ./proj/:/home/node/app
      - /home/node/app/node_modules/
    ports:
      - "3006:3001"
    command: >
      /bin/sh -c "echo hello
      && ls -lh /home/node/app/
      && npm install
      && npm i -g babel-cli
      && npm i -g flow-bin
      && npm start"
    depends_on:
      - redis