anchor.diff:  ##################################
   # Selfie interactive final image #
   ##################################
  -FROM ubuntu:18.04
  +FROM ubuntu:rolling
   
   # specify work directory and RISC-V install directory
   ENV TOP=/opt RISCV=/opt/riscv PATH=$PATH:/opt/riscv/bin
  
positive.code: ###################################
  # PK (Proxy kernel) builder image #
  ###################################
  FROM ubuntu:18.10 AS pkbuilder
  
  # specify work directory and RISC-V install directory
  ENV TOP=/opt RISCV=/opt/riscv PATH=$PATH:/opt/riscv/bin
  
negative.code: RUN make selfie
  
  # default command
  CMD /bin/bash
  