Rails Web application on Docker Debian

Dockerfile

FROM debian:8.5

## Image metadata ##

MAINTAINER Stuart Ellis, stuart@stuartellis.eu
LABEL description="Rails Web application on Debian"

## Application user account ##

ENV APP_USER app
RUN useradd -d /home/$APP_USER -m $APP_USER && \
    chown -R $APP_USER:$APP_USER /home/$APP_USER

## Debian packages ##

# App dependencies first, so that they are not uninstalled by autoremove:
#  * The Nokogiri gem requires libxml2
#  * Ruby on Rails requires Node.js for asset compilation
#  * Rails applications may use Ghostscript, Imagemagick and the MySQL client
ENV APP_DEPS ca-certificates ghostscript imagemagick monit sudo \
  libxml2 libxslt1.1 libyaml-0-2 \
  mysql-client nodejs openssl

RUN apt-get update && apt-get install -y --no-install-recommends $APP_DEPS

ENV BUILD_DEPS autoconf automake bison libtool make g++ \
    bzip2 curl git sqlite3 \
    libcurl4-openssl-dev libffi-dev libgdbm-dev \
    libmagickcore-dev libmagickwand-dev libmysqlclient-dev libncurses5-dev \
    libreadline-dev libsqlite3-dev libssl-dev libxml2-dev libxslt1-dev \
    libyaml-dev zlib1g-dev

RUN apt-get install -y --no-install-recommends $BUILD_DEPS && \
    apt-get autoremove -y && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

## Install Ruby ##

ENV RUBY_VERSION 2.3.1

### Install ruby-build ###
RUN git clone https://github.com/rbenv/ruby-build.git /tmp/ruby-build --depth 1 && \
    cd /tmp/ruby-build && \
    ./install.sh && \
    cd / && \
    rm -rf /tmp/ruby-build

### Install Ruby using ruby-build ###
# Setting to disable generation of Ruby documentation with ruby-build
ENV CONFIGURE_OPTS --disable-install-rdoc
RUN ruby-build -v $RUBY_VERSION /usr/local
RUN gem install bundler --without development --no-rdoc --no-ri

## Monit configuration ##

COPY bin/delayed_job_srv /etc/init.d/
COPY ["config/monit/delayed_job.conf", "config/monit/monit_http.conf", "/etc/monit/conf.d/"]
COPY config/monit/monit_sudo /etc/sudoers.d/
RUN chown -R root:root /etc/init.d/delayed_job_srv && \
  chmod 0755 /etc/init.d/delayed_job_srv && \
  chown -R root:root /etc/monit/conf.d/delayed_job.conf && \
  chmod 0644 /etc/monit/conf.d/delayed_job.conf && \
  chown -R root:root /etc/monit/conf.d/monit_http.conf && \
  chmod 0644 /etc/monit/conf.d/monit_http.conf && \
  chown -R root:root /etc/sudoers.d/monit_sudo && \
  chmod 0440 /etc/sudoers.d/monit_sudo

## Application ##

### Set up a working directory inside the image ###
ENV APP_HOME /usr/src/app
RUN mkdir $APP_HOME && chown -R $APP_USER:$APP_USER $APP_HOME

### Use the application working directory ###
WORKDIR $APP_HOME

### Install gem packages for the application ###
COPY Gemfile* $APP_HOME/
RUN bundle config build.nokogiri --use-system-libraries && \
    bundle install --deployment --without development

### Populate the application working directory ###
COPY . $APP_HOME
RUN chown -R $APP_USER:$APP_USER $APP_HOME

# Switch to the unprivileged user account
USER $APP_USER

### Pre-compile the assets for the application ###
RUN bin/rake assets:precompile

## Container default settings ##

EXPOSE 3000 5627
CMD ["bin/docker_cmd"]