anchor.diff:  
   # https://github.com/kubernetes/kops/blob/master/channels/stable
   # https://github.com/kubernetes/kops/blob/master/docs/images.md
  -ENV KOPS_BASE_IMAGE=kope.io/k8s-1.7-debian-jessie-amd64-hvm-ebs-2017-07-28
  +ENV KOPS_BASE_IMAGE=kope.io/k8s-1.9-debian-jessie-amd64-hvm-ebs-2018-03-11
   
   ENV KOPS_BASTION_PUBLIC_NAME="bastion"
   ENV KOPS_PRIVATE_SUBNETS="172.20.32.0/19,172.20.64.0/19,172.20.96.0/19,172.20.128.0/19"
  
positive.code: #
  # Install kops
  #
  ENV KOPS_VERSION 1.8.0
  ENV KOPS_STATE_STORE s3://undefined
  ENV KOPS_STATE_STORE_REGION us-east-1
  ENV KOPS_FEATURE_FLAGS=+DrainAndValidateRollingUpdate
  
negative.code: # Install kubectl
  #
  ENV KUBECONFIG=${SECRETS_PATH}/kubernetes/kubeconfig
  ENV KUBERNETES_VERSION 1.9.1
  RUN curl --fail -sSL -O https://storage.googleapis.com/kubernetes-release/release/v${KUBERNETES_VERSION}/bin/linux/amd64/kubectl \
      && mv kubectl /usr/local/bin/kubectl \
      && chmod +x /usr/local/bin/kubectl \
  