anchor.diff:  # Customization for user and location
   ########################################################
   # Set up user so that we do not run as root
  -ENV LANG=en_US.UTF-8 \
  -    LANGUAGE=en_US:en \
  -    LC_ALL=en_US.UTF-8
  -
   ENV DOCKER_USER=ubuntu \
       DOCKER_SHELL=/usr/bin/zsh
   
  
positive.code:     DOCKER_HOME=/home/$DOCKER_USER \
      HOME=/home/$DOCKER_USER
  
  # Change the default timezone to America/New_York
  # Disable forward logging (https://github.com/phusion/baseimage-docker/issues/186)
  # Run ldconfig so that /usr/local/lib etc. are in the default
  # search path for dynamic linker
  RUN useradd -m -s $DOCKER_SHELL -G sudo,docker_env $DOCKER_USER && \
      echo "$DOCKER_USER:docker" | chpasswd && \
      echo "$DOCKER_USER ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers && \
      echo "America/New_York" > /etc/timezone && \
      ln -s -f /usr/share/zoneinfo/America/New_York /etc/localtime && \
      touch /etc/service/syslog-forwarder/down && \
      ldconfig
  
  
negative.code: FROM x11vnc/baseimage:0.9.22
  LABEL maintainer Xiangmin Jiao <xmjiao@gmail.com>
  
  ARG DOCKER_LANG=en_US
  ARG DOCKER_TIMEZONE=America/New_York
  
  ENV LANG=$DOCKER_LANG.UTF-8 \
      LANGUAGE=$DOCKER_LANG:UTF-8 \
      LC_ALL=$DOCKER_LANG.UTF-8
  
  WORKDIR /tmp
  
  ARG DEBIAN_FRONTEND=noninteractive
  
  # Install some required system tools and packages for X Windows
  RUN locale-gen $LANG && \
      dpkg-reconfigure -f noninteractive locales && \
      apt-get update && \
      apt-get install -y --no-install-recommends \
          man \
          sudo \
  