baseboard-gru/scripts/disk_layout.json

{
  "_comment": "See http://www.chromium.org/chromium-os/developer-guide/disk-layout-format",
  "metadata":{
    "rootdev_base": "/sys/devices/platform/fe330000.sdhci/mmc_host/mmc*/mmc*/block/mmcblk*"
  },
  "parent": "legacy_disk_layout.json",
  "layouts":{
    # Used for factory install images. No need to adjust fs size or partition
    # size since these do not need more space.
    "factory_install": [
      {
        "num": 3,
        "fs_size_min": "0 MiB",
        "size_min": "0 MiB"
      }
    ]
  }
}