anchor.diff:  ENV FS_OVERRIDE 0
   ENV FIX_VERTEX_AREA=
   ENV SUBJECTS_DIR /opt/freesurfer/subjects
  +ENV FUNCTIONALS_DIR /opt/freesurfer/sessions
   ENV FSF_OUTPUT_FORMAT nii.gz
   ENV MNI_DIR /opt/freesurfer/mni
   ENV LOCAL_DIR /opt/freesurfer/local
  
positive.code: # Precaching fonts
  RUN python -c "from matplotlib import font_manager"
  
  # Unless otherwise specified each process should only use one thread - nipype
  # will handle parallelization
  ENV MKL_NUM_THREADS=1
  
negative.code: # Use Ubuntu 16.04 LTS
  FROM ubuntu:xenial-20161213
  
  # Prepare environment
  RUN apt-get update && \
      apt-get install -y --no-install-recommends curl bzip2 ca-certificates xvfb && \
      curl -sSL http://neuro.debian.net/lists/xenial.us-ca.full >> /etc/apt/sources.list.d/neurodebian.sources.list && \
      apt-key adv --recv-keys --keyserver hkp://pgp.mit.edu:80 0xA5D32F012649A5A9 && \
      apt-get update
  
  # Installing freesurfer
  RUN curl -sSL https://surfer.nmr.mgh.harvard.edu/pub/dist/freesurfer/6.0.0/freesurfer-Linux-centos6_x86_64-stable-pub-v6.0.0.tar.gz | tar zxv -C /opt \
  