I have a Dockerfile I'm pointing at from a docker-compose.yml.
I'd like the volume mount in the docker-compose.yml to happen before the RUN in the Dockerfile.
Dockerfile:
FROM node WORKDIR /usr/src/app RUN npm install --global gulp-cli \ && npm install ENTRYPOINT gulp watch
docker-compose.yml
version: '2' services: build_tools: build: docker/gulp volumes_from: - build_data:rw build_data: image: debian:jessie volumes: - .:/usr/src/app
It makes complete sense for it to do the Dockerfile first, then mount from docker-compose, however is there a way to get around it.
I want to keep the Dockerfile generic, while passing more specific bits in from compose. Perhaps that's not the best practice?
Erik Dannenberg's is correct, the volume layering means that what I was trying to do makes no sense. (There is another really good explaination on the Docker website if you want to read more). If I want to have Docker do the npm install then I could do it like this:
FROM node ADD . /usr/src/app WORKDIR /usr/src/app RUN npm install --global gulp-cli \ && npm install CMD ["gulp", "watch"]
However, this isn't appropriate as a solution for my situation. The goal is to use NPM to install project dependencies, then run gulp to build my project. This means I need read and write access to the project folder and it needs to persist after the container is gone.
I need to do two things after the volume is mounted, so I came up with the following solution...
docker/gulp/Dockerfile:
FROM node RUN npm install --global gulp-cli ADD start-gulp.sh . CMD ./start-gulp.sh
docker/gulp/start-gulp.sh:
#!/usr/bin/env bash until cd /usr/src/app && npm install do echo "Retrying npm install" done gulp watch
docker-compose.yml:
version: '2' services: build_tools: build: docker/gulp volumes_from: - build_data:rw build_data: image: debian:jessie volumes: - .:/usr/src/app
So now the container starts a bash script that will continuously loop until it can get into the directory and run npm install. This is still quite brittle, but it works. :)
You can't mount host folders or volumes during a Docker build. Allowing that would compromise build repeatability. The only way to access local data during a Docker build is the build context, which is everything in the PATH or URL you passed to the build command. Note that the Dockerfile needs to exist somewhere in context. See https://docs.docker.com/engine/reference/commandline/build/ for more details.
