Dockerfile for ubuntu 18.04 based system with Rails and SSH

Dockerfile

FROM ubuntu:18.04
LABEL mantainer='Amanda Santana'

RUN apt-get update 
RUN apt-get install -y openssh-server vim curl git sudo zip

RUN apt-get update
RUN apt-get install -y build-essential automake autoconf \
                       bison libssl-dev libyaml-dev libreadline6-dev \
                       zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev \
                       gawk g++ gcc make libc6-dev patch libsqlite3-dev sqlite3 \
                       libtool pkg-config libpq-dev nodejs ruby-full

RUN mkdir /var/run/sshd

RUN echo 'root:root' |chpasswd
RUN sed -ri 's/^#?PermitRootLogin\s+.*/PermitRootLogin yes/' /etc/ssh/sshd_config
RUN sed -ri 's/UsePAM yes/#UsePAM yes/g' /etc/ssh/sshd_config

RUN useradd -ms /bin/bash app
RUN adduser app sudo
RUN echo 'app:app' |chpasswd

USER app

RUN /bin/bash -l -c "echo 'export PATH=$HOME/.rbenv/shims:$HOME/.rbenv/bin:$PATH' >> $HOME/.bashrc"
RUN /bin/bash -l -c "echo 'export PATH=$HOME/.rbenv/shims:$HOME/.rbenv/bin:$PATH' >> $HOME/.profile"
RUN /bin/bash -l -c 'source $HOME/.bashrc'
RUN /bin/bash -l -c "curl -fsSL https://github.com/rbenv/rbenv-installer/raw/master/bin/rbenv-installer | bash"
RUN /bin/bash -l -c "rbenv install 2.7.0"
RUN /bin/bash -l -c "rbenv global 2.7.0"
RUN /bin/bash -l -c "echo 'gem: --no-document' > ~/.gemrc "
RUN /bin/bash -l -c "gem install bundler --no-document"
RUN /bin/bash -l -c "gem install rails -v 6.0.2.1"

USER root

RUN mkdir /workspace
VOLUME /workspace

RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

EXPOSE 22
EXPOSE 3000

CMD    ["/usr/sbin/sshd", "-D"]