anchor.diff:  RUN ${PREFIX_DIR}/bin/build-guacd.sh "$BUILD_DIR" "$PREFIX_DIR"
   
   # Record the packages of all runtime library dependencies
  -RUN ${PREFIX_DIR}/bin/list-dependencies.sh    \
  -        ${PREFIX_DIR}/sbin/guacd              \
  -        ${PREFIX_DIR}/lib/libguac-client-*.so \
  -        ${PREFIX_DIR}/lib/freerdp2/guac*.so   \
  +RUN ${PREFIX_DIR}/bin/list-dependencies.sh     \
  +        ${PREFIX_DIR}/sbin/guacd               \
  +        ${PREFIX_DIR}/lib/libguac-client-*.so  \
  +        ${PREFIX_DIR}/lib/freerdp2/*guac*.so   \
           > ${PREFIX_DIR}/DEPENDENCIES
   
   # Use same Debian as the base for the runtime image
  -FROM debian:${DEBIAN_VERSION}-slim
  +FROM debian:${DEBIAN_BASE_IMAGE}
   
  -# Base directory for installed build artifacts.
  -# Due to limitations of the Docker image build process, this value is
  -# duplicated in an ARG in the first stage of the build. See also the
  +#
  +# The Debian repository that should be preferred for dependencies (this will be
  +# added to /etc/apt/sources.list if not already present)
  +#
  +# NOTE: Due to limitations of the Docker image build process, this value is
  +# duplicated in an ARG in the first stage of the build.
  +#
  +ARG DEBIAN_RELEASE=buster-backports
  +
  +# Add repository for specified Debian release if not already present in
  +# sources.list
  +RUN grep " ${DEBIAN_RELEASE} " /etc/apt/sources.list || echo >> /etc/apt/sources.list \
  +    "deb http://deb.debian.org/debian ${DEBIAN_RELEASE} main contrib non-free"
  +
  +#
  +# Base directory for installed build artifacts. See also the
   # CMD directive at the end of this build stage.
  +#
  +# NOTE: Due to limitations of the Docker image build process, this value is
  +# duplicated in an ARG in the first stage of the build.
   #
   ARG PREFIX_DIR=/usr/local/guacamole
   
  
positive.code:         fonts-dejavu                  \
          xfonts-terminus"
  
  # Copy build artifacts into this stage
  COPY --from=builder ${PREFIX_DIR} ${PREFIX_DIR}
  
  # Bring runtime environment up to date and install runtime dependencies
  RUN apt-get update                                                                  && \
      apt-get install -y --no-install-recommends $RUNTIME_DEPENDENCIES                && \
      apt-get install -y --no-install-recommends $(cat "${PREFIX_DIR}"/DEPENDENCIES)  && \
      rm -rf /var/lib/apt/lists/*
  
  # Link FreeRDP plugins into proper path
  
negative.code: # Dockerfile for guacamole-server
  #
  
  # The Debian image that should be used as the basis for the guacd image
  ARG DEBIAN_BASE_IMAGE=buster-slim
  
  # Use Debian as base for the build
  FROM debian:${DEBIAN_BASE_IMAGE} AS builder
  
  #
  # The Debian repository that should be preferred for dependencies (this will be
  # added to /etc/apt/sources.list if not already present)
  #
  # NOTE: Due to limitations of the Docker image build process, this value is
  # duplicated in an ARG in the second stage of the build.
  #
  ARG DEBIAN_RELEASE=buster-backports
  
  # Add repository for specified Debian release if not already present in
  # sources.list
  RUN grep " ${DEBIAN_RELEASE} " /etc/apt/sources.list || echo >> /etc/apt/sources.list \
      "deb http://deb.debian.org/debian ${DEBIAN_RELEASE} main contrib non-free"
  
  #
  # Base directory for installed build artifacts.
  #
  # NOTE: Due to limitations of the Docker image build process, this value is
  # duplicated in an ARG in the second stage of the build.
  #
  ARG PREFIX_DIR=/usr/local/guacamole
  