Dockerfile Ruby 2.3.3 with UTF-8 UNICODE support and without ROOT

Dockerfile

FROM ruby:2.3.3

RUN apt-get update &&\
    # add support to unicode chars from keyboard: ç,ã,ô:
    apt-get install -y locales \
    # JavaScript runtime to uglifier:
                       nodejs \
                       # rails dbconsole
                       # psql \
    # Required by rails-erd
                       graphviz &&\
    echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && /usr/sbin/locale-gen &&\
    rm -rf /var/lib/apt/lists/*

ENV LANG en_US.UTF-8
ENV LANGUAGE en_US.UTF-8
ENV LC_ALL en_US.UTF-8

ENV APP_ROOT /app

RUN mkdir $APP_ROOT

WORKDIR $APP_ROOT

RUN groupadd -r app &&\
    groupmod -g 1000 app &&\
    useradd -g app -ms /bin/bash app &&\
    chown -R app:app $APP_ROOT

USER app