Use rbenv on ubuntu (memo for the case that could not use a ruby image for some reason)

Dockerfile

FROM ubuntu

# prepare packages
RUN apt-get update \
 && apt-get upgrade -y \
 && apt-get install -y git \
 && apt-get build-dep -y ruby

# set timezone
RUN echo "Asia/Tokyo" > /etc/timezone \
 && dpkg-reconfigure -f noninteractive tzdata

# set locale
RUN /usr/sbin/locale-gen ja_JP.UTF-8

# add login user
RUN useradd -m -G sudo ubuntu

USER ubuntu

# install rbenv
RUN git clone https://github.com/rbenv/rbenv.git ~/.rbenv \
 && git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build \
 && echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile \
 && echo 'eval "$(rbenv init -)"' >> ~/.bash_profile

# install ruby
RUN bash -l -c "rbenv install 2.3.1"

EXPOSE 80
CMD ["echo", "hello"]