Dockerfile
# Base our image on an official, minimal image of our preferred Ruby
FROM ruby:2.4-alpine
# Install essential Linux packages
RUN apk update && apk upgrade
RUN apk add build-base postgresql-dev postgresql-client tzdata file imagemagick
# Define where our application will live inside the image
ENV RAILS_ROOT /pixnyannyan
# Create application home. App server will need the pids dir so just create everything in one shot
RUN mkdir -p $RAILS_ROOT/tmp/pids
# Set our working directory inside the image
WORKDIR $RAILS_ROOT
# Use the Gemfiles as Docker cache markers. Always bundle before copying app src.
# (the src likely changed and we don't want to invalidate Docker's cache too early)
# http://ilikestuffblog.com/2014/01/06/how-to-skip-bundle-install-when-deploying-a-rails-app-to-docker/
ADD Gemfile Gemfile
ADD Gemfile.lock Gemfile.lock
# Prevent bundler warnings; ensure that the bundler version executed is >= that which created Gemfile.lock
RUN gem install bundler
# Finish establishing our Ruby enviornment
RUN bundle install --deployment --without development test
# Copy the Rails application into place
ADD . .
# Define the script we want run once the container boots
# Use the "exec" form of CMD so our script shuts down gracefully on SIGTERM (i.e. `docker stop`)
EXPOSE 3000
CMD $RAILS_ROOT/app_cmd.sh