CODEWITHSUNDEEP
windowsdockercontainersdockerfile
matan tsuberi
matan tsuberi

Reputation: 145

Docker: mounting a volume overwrites container

I'm trying to write a Dockerfile for use as a standardized development environment.

Dockerfile:

FROM node:9.5.0

WORKDIR /home/project

# install some stuff...

# clone the repo
RUN git clone https://github.com/... . 

# expose 
VOLUME /home/project

# fetch latest changes from git, install them and fire up a shell.
CMD git pull && npm install && /bin/bash

After building the image (say with tag dev), Running docker run -it dev gives me a shell with the project installed and up-to-date.

Of course changes I make in the container are ephemeral so I want to mount /home/project on the host OS, I go to an empty directory project on the host and run:

docker run -it -v ${pwd}:/home/project dev

But my project folder gets overwritten and is empty inside the container.

How can mount the volume such that the container writes to the host folder and not the opposite?

OS: Windows 10 Pro.

Upvotes: 2

Views: 1801

Answers (2)

scelikcapa
scelikcapa

Reputation: 1

If you need a dev environment to test your code, there is no need to clone the repo from git. You only need to COPY package*.json file from host to image to install dependencies.

First, open your project folder in the host machine with IDE. Add a file named Dockerfile to your project main folder as below:

FROM node:9.5.0

WORKDIR /home/project

COPY package*.json ./

Also, CMD commands work while the image is starting. If you want to install dependencies while the image is being created, add RUN command

RUN npm install

# start your app
CMD [ "node", "app.js" ]

Now the only thing you need is to bind your project folder (on host) to the project folder (on the container). To do this, create the container with this PowerShell command:

docker run -it -v ${pwd}:/home/project dev

if your are using windows command line, use this instead:

docker run -it -v "%cd%:/home/project dev

if you want to open any port, add -p parameter:

docker run -it -p 1234:1234 -v ${pwd}:/home/project dev

Upvotes: 0

Shahriar
Shahriar

Reputation: 13804

When you mount a volume, read/write are both bi-directional by default. That means that anything you write in the container will show up in the host directory and vice versa.

But something weird is happening in your case, right?

In your build process, you are cloning a git repository. During the build process, the volume does not get mounted. The git data resides in your docker image.

Now, when you are running the docker container, you are mounting the volume. The mount path in your container will be synced with your source path. That means the container directory will be overwritten with the contents of the host directory. That's why your git data has been lost.

Possible Solution:

Run a script as CMD. That script can clone the git repo, among other things.

run.sh

#!/bin/bash

# clone the repo
RUN git clone https://github.com/... .

Dockerfile

RUN ADD run.sh /bin

# run run.sh, install them and fire up a shell.
CMD run.sh && npm install && /bin/bash

Upvotes: 2

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