anchor.diff:  RUN /command/core-package-install mksh
   RUN /command/core-package-install
   
  +
   ################################################################################
   # Services
   ################################################################################
   
   # password set in sshd/run script at ssh start. allows for override via env var.
  -RUN \
  -  set -e; groupadd --system airstack --gid 432; \
  +RUN set -e; \
  +  groupadd --system airstack --gid 432; \
     useradd --uid 431 --system --base-dir /home --create-home --gid airstack --shell /bin/nologin --comment "airstack user" airstack; \
     chown -R airstack:airstack /home/airstack
   
  -# passwordless sudo enabled for airstack user. should only do for development environment.
  -# RUN [ $AIRSTACK_TAGS_ENV = "development" ] && echo "airstack  ALL = NOPASSWD: ALL" > /etc/sudoers.d/airstack && usermod --shell /bin/bash airstack
  -RUN \
  -  set -e; echo "airstack  ALL = NOPASSWD: ALL" > /etc/sudoers.d/airstack; \
  +# TODO: passwordless sudo enabled for airstack user. should only do for development environment.
  +#       RUN [ $AIRSTACK_TAGS_ENV = "development" ] && echo "airstack  ALL = NOPASSWD: ALL" > /etc/sudoers.d/airstack && usermod --shell /bin/bash airstack
  +RUN set -e; \
  +  echo "airstack  ALL = NOPASSWD: ALL" > /etc/sudoers.d/airstack; \
     usermod --shell /bin/bash airstack
   
   #runit install
  
positive.code: RUN /command/core-package-install haproxy
  
  # Packages::serf
  RUN \
    set -e; \
    VER="0.6.3"; PKG_NAME="serf" PKG_DIR="/package/$PKG_NAME"; mkdir -vp "$PKG_DIR-$VER"/command; \
    cd $PKG_DIR-$VER; \
    wget -v -O "$PKG_NAME-$VER".zip https://dl.bintray.com/mitchellh/serf/"$VER"_linux_amd64.zip; \
  
negative.code: 
  ################################################################################
  # DEBUG
  ################################################################################
  
  # TODO: remove this later. /command symlinks should be setup by each command.
  RUN ln -vs /command/core-* /usr/local/bin/
  
  
  ################################################################################
  