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. 🙂