anchor.diff:      rm bigdl*.zip
   
   # stage.3 copies layer
  -FROM ubuntu:18.04 as copies-layer
  +FROM ubuntu:20.04 as copies-layer
   ARG BIGDL_VERSION
  +ARG DEBIAN_FRONTEND
   
   COPY --from=bigdl /opt/bigdl-${BIGDL_VERSION} /opt/bigdl-${BIGDL_VERSION}
   COPY --from=spark /opt/jdk /opt/jdk
  
positive.code: ARG BIGDL_VERSION=0.14.0-SNAPSHOT
  ARG TINI_VERSION=v0.18.0
  ARG PYTHON_ENV_NAME=tf1
  
  # stage.1 jdk & spark
  FROM ubuntu:18.04 as spark
  ARG SPARK_VERSION
  ARG HADOOP_VERSION
  ARG JDK_VERSION
  ARG JDK_URL
  ARG SPARK_HOME
  ARG TINI_VERSION
  ENV TINI_VERSION                        ${TINI_VERSION}
  ENV SPARK_VERSION                       ${SPARK_VERSION}
  
negative.code: 
  
  # stage.4
  FROM ubuntu:20.04
  MAINTAINER The BigDL Authors https://github.com/intel-analytics/BigDL
  ARG BIGDL_VERSION
  ARG SPARK_VERSION
  ARG SPARK_HOME
  ARG TINI_VERSION
  ARG PYTHON_ENV_NAME
  ARG DEBIAN_FRONTEND
  
  ENV BIGDL_HOME                          /opt/bigdl-${BIGDL_VERSION}
  ENV BIGDL_VERSION                       ${BIGDL_VERSION}
  