anchor.diff:  ENV DOWNLOAD_URL http://downloads.asterisk.org/pub/telephony/certified-asterisk
   ENV ASTVERSION certified-asterisk-13.1-cert2
   ENV TARGET_DIR /usr/src/
  -ENV PKG_LIST automake \
  +ENV DEV_PKG_LIST automake \
       gcc \
       gcc-c++ \
       ncurses-devel \
  
positive.code: # clean up
  WORKDIR $TARGET_DIR
  RUN rm -rf $ASTVERSION
  RUN yum remove -y -q tar $PKG_LIST && yum autoremove -y && yum clean all
  
  # start the system
  WORKDIR /usr/sbin
  
negative.code:     libuuid-devel \
      gsm-devel
  
  ENV RUN_PKG_LIST pjproject jansson neon unixODBC vorbis
  
  # install dependencies
  RUN yum -q makecache && yum install tar epel-release -y && yum install -q -y $DEV_PKG_LIST $RUN_PKG_LIST
  
  # obtain and extract the source
  WORKDIR $TARGET_DIR
  