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Making volumes with Docker-Compose

(Xoancosmed) #1

I am trying to use Docker to make an API with NodeJS. This is how the directory of my project looks like:

  • Dockerfile
  • docker-compose.yml
  • package.json
  • server.js
  • online_app/ (empty folder)

What I want to do is to have an “online_app” folder which will contain the files of my projects. The problem is that when I try to map this folder as a volume, NodeJS fails because it don’t find the “server.js” and “package.json” file. This is the content of the files (I think that the mistake should be in the “docker-compose.yml” or in the “Dockerfile”:


FROM node

RUN mkdir /app

COPY . /app
RUN npm install


CMD ["npm", "start"]


version: "2"

    build: .
      - ./online_app:/app
      - "8080"
      - VIRTUAL_PORT=8080
    image: mongo
      - "27017:27017"
      name: proxy_net


  "name": "node_server",
  "version": "0.0.1",
  "description": "",
  "main": "server.js",
  "scripts": {
    "start": "nodemon server.js"
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.2",
    "mongoose": "^5.0.3",
    "nodemon": "^1.14.12"


var express = require('express');
var app = express();

var db = require('mongoose');

app.get('/', function(req, res){
  res.send("Hello World!<br>\nHola Mundo!<br>\n");

app.listen(8080, function(){
  console.log('Node app listening on port 8080!');

(Sam) #2

i don’t quite understand…

the volumes

      - ./:/app 

means to map the current directory (./) to the containers /app folder…
this will overlay the /app folder in the container (the good stuff) with whatever
is in the current directory at the time of docker-compose up

but… you have already copied . into /app during build

also, why copy the package file only then copy everything later

COPY package.json /app
RUN npm install

COPY . /app

just copy everything and THEN do the npm install.

(Xoancosmed) #3

Sorry, I copied the wrong “docker-compose.yml” file. I corrected it in my first post:

       - ./online_app:/app

You are right, I should only copy the package.json ones. I have corrected it in the first post, but I still have problems with the mapping of the folder …

The thing is that I copy all these files in the Dockerfile (when I do “COPY . /app”), but when the volume is mounted, all that files are missing …

(Sam) #4

right,… you overlayed the internal /app (built at image build time) files with whatever is in ./online_app at run time…

(Xoancosmed) #5

Ahhh … now I understand. Sorry for my ignorance, but there is a way to do the reverse thing? I mean, it is possible that the content of the “/app” directory of the container is preserved instead of the content in the “online_app” (in the host)?

Thanks for your reply

(Sam) #6

don’t mount the volume, or mount it someplace else…

what does online_app add to the node application?

(Xoancosmed) #7

I was planning to use the “online_app” folder to keep always a copy of the original code. But as this does not work as I supposed, I think that I am going to pass …

Thanks for your help :wink: