Running chown in Dockerfile does nothing - linux

Question

I'm having some trouble setting up a Nuxt and Rails container using Docker. The two containers are separate, but interact with each other.
Currently, I'm having trouble running the dev servers for both the Nuxt and the Rails containers due to insufficient permissions. Looking at the logs for both of the containers, it seems that Docker can't do actions such as mkdir.
EACCESS: Permission Denied: 'mkdir: /usr/src/app/.nuxt' # nuxt
EACCESS: Permission Denied: 'mkdir: /usr/src/app/tmp' # rails
My docker-compose.dev.yml file
version: 3
services:
backend:
privileged: true
image: tablevibes-backend
build:
dockerfile: Dockerfile-dev
context: tablevibes-backend
args:
UID: ${UID:-1001}
BUNDLER_VERSION: 2.0.2
PG_MAJOR: 10
mode: development
tty: true
stdin_open: true
volumes:
- ./tablevibes-backend:/usr/src/app:Z
- gem_data_api:/usr/local/bundle:cached
ports:
- "3000:3000"
depends_on:
- db
user: rails
client-ui:
image: client-ui
command: yarn run dev
build:
context: client-ui
dockerfile: Dockerfile-dev
args:
UID: ${UID:-1001}
PORT: 5000
MODE: DEV
restart: always
volumes:
- ./client-ui:/usr/src/app
- client_ui_node_modules:/usr/src/app/node_modules:cached
ports:
- 5000:5000
user: client-ui
The 2 Dockerfiles
The Rails Dockerfile-dev
FROM ruby:2.6.3
ARG PG_MAJOR
ARG BUNDLER_VERSION
ARG UID
ARG MODE
RUN adduser rails --uid $UID --disabled-password --gecos ""
# Add POSTGRESQL to the source list using the right version
RUN curl -sSL https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
&& echo 'deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main' $PG_MAJOR > /etc/apt/sources.list.d/pgdg.list
ENV RAILS_ENV $MODE
RUN apt-get update -qq && apt-get install -y postgresql-client-$PG_MAJOR vim
RUN apt-get -y install sudo
WORKDIR /usr/src/app
CMD chown -R rails /usr/src/app
COPY Gemfile /usr/src/app/Gemfile
COPY Gemfile.lock /usr/src/app/Gemfile.lock
ENV BUNDLER_VERSION $BUNDLER_VERSION
RUN gem install bundler:$BUNDLER_VERSION
RUN bundle install
COPY . /usr/src/app
# Add a script to be executed every time the container starts.
COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
EXPOSE 3000
# Start the main process.
CMD ["rails", "server", "-b", "0.0.0.0"]
The Nuxt Dockerfile-dev
FROM node:10
ARG UID
ARG MODE=DEV
ARG PORT
RUN adduser client-ui --uid $UID --disabled-password --gecos ""
RUN apt-get update
RUN apt-get -y install sudo
RUN mkdir /usr/src/app
RUN chown -R client-ui /usr/src/app
COPY package.json yarn.lock /usr/src/app
RUN yarn install
COPY . /usr/src/app
ENV API_URL=http://localhost:3000/v1
ENV REVIEW_URL=http://localhost:8000
# expose 5000 on container
EXPOSE $PORT
# set app serving to permissive / assigned
ENV NUXT_HOST=0.0.0.0
# set app port
ENV NUXT_PORT=$PORT
My problem is that those lines where I do RUN chown ... never seem to take place. If I manually go into the containers with docker exec -u root -it backend bash and run chown -R rails . manually, everything works as expected. Likewise I tried running chmod 777 as a test, however that also had no effect on the permission denied error I keep getting.
What might be causing Docker to ignore my chown command?
This Stack Overflow question seems relevant, however it doesn't quite apply because I don't have any VOLUME mounts inside my Dockerfiles. A user in the comments of the accepted answer has my same issue, though unfortunately no solution.

Answer 1

Containers are like ogres, or onions, they have layers.
When using VOLUMEs or MOUNTs, the directory (or file) is not actually IN the container, but only appears to be in it.
Your Dockerfile uses a layer for /usr/src/app, which as you probably already know is your ./tablevibes-backend directory on your host computer.
services:
backend:
volumes:
- ./tablevibes-backend:/usr/src/app:Z
When you use a volume or mount in this way, the only thing Docker can do is simple CRUD (create, read, update, delete) options, it can not (and should not) modify the metadata as it is modifying your host drive, which could be a security issue.

Answer 2

try this:
sudo chown -R $USER:$USER .