anchor.diff:  ARG BIGDL_VERSION=0.14.0-SNAPSHOT
   ARG TINI_VERSION=v0.18.0
   ARG PYTHON_ENV_NAME=tf1
  +ARG DEBIAN_FRONTEND=noninteractive
   
   # stage.1 jdk & spark
  -FROM ubuntu:18.04 as spark
  +FROM ubuntu:20.04 as spark
   ARG SPARK_VERSION
   ARG HADOOP_VERSION
   ARG JDK_VERSION
   ARG JDK_URL
   ARG SPARK_HOME
  +ARG DEBIAN_FRONTEND
   ARG TINI_VERSION
   ENV TINI_VERSION                        ${TINI_VERSION}
   ENV SPARK_VERSION                       ${SPARK_VERSION}
  
positive.code:     rm bigdl*.zip
  
  # stage.3 copies layer
  FROM ubuntu:18.04 as copies-layer
  ARG BIGDL_VERSION
  
  COPY --from=bigdl /opt/bigdl-${BIGDL_VERSION} /opt/bigdl-${BIGDL_VERSION}
  COPY --from=spark /opt/jdk /opt/jdk
  
negative.code: RUN git clone https://github.com/tensorflow/models/ /opt/models
  
  # stage.2 bigdl
  FROM ubuntu:20.04 as bigdl
  ARG SPARK_VERSION
  ARG BIGDL_VERSION
  ARG DEBIAN_FRONTEND
  ENV SPARK_VERSION               ${SPARK_VERSION}
  ENV BIGDL_VERSION               ${BIGDL_VERSION}
  ENV BIGDL_HOME                  /opt/bigdl-${BIGDL_VERSION}
  