default ruby/rails Dockerfile with alpine

Dockerfile

FROM ruby:2.3-alpine
MAINTAINER Joao Tarla <joao@tarla.com.br>

ENV BUILD_PACKAGES="curl-dev ruby-dev build-base bash" \
    DEV_PACKAGES="zlib-dev libxml2-dev libxslt-dev tzdata yaml-dev postgresql-dev" \
    RUBY_PACKAGES="ruby-json yaml nodejs"

RUN apk --update add --no-cache --update\
    $BUILD_PACKAGES \
    $DEV_PACKAGES \
    $RUBY_PACKAGES && \
    rm -rf /var/cache/apk/* && \
    mkdir -p /usr/src/app

ONBUILD WORKDIR /usr/src/app
ONBUILD COPY . /usr/src/app
ONBUILD EXPOSE 9000
ONBUILD RUN bundle config build.nokogiri --use-system-libraries && \
            bundle install && \
            bundle clean

WORKDIR /usr/src/app/
CMD ["rails", "server", "-b", "0.0.0.0", "-p", "9000"]