anchor.diff:  
     boot.kernelParams = [ "console=ttyS0" ];
   
  -  boot.initrd.kernelModules = [ "aufs" ];
  -
  -  boot.extraModulePackages = [ config.boot.kernelPackages.aufs ];
  -
     boot.loader.grub.version = 2;
     boot.loader.grub.device = "/dev/vda";
     boot.loader.grub.timeout = 0;
  
positive.code:       mkdir -m 755 -p $targetRoot/var
        mount --bind $targetRoot/ephemeral0/var $targetRoot/var
  
        mkdir -m 755 -p $targetRoot/ephemeral0/nix
        mount -t aufs -o dirs=$targetRoot/ephemeral0/nix=rw:$targetRoot/nix=rr none $targetRoot/nix
      '';
      */
  
    # Since Nova allows VNC access to instances, it's nice to start to
  
negative.code:   # Put /tmp and /var on /ephemeral0, which has a lot more space.
    # Unfortunately we can't do this with the `fileSystems' option
    # because it has no support for creating the source of a bind
    # mount.  Also, "move" /nix to /ephemeral0 by layering a unionfs-fuse
    # mount on top of it so we have a lot more space for Nix operations.
    /*
    boot.initrd.postMountCommands =
      ''
  