baseboard-oak/scripts/disk_layout.json

{
  "_comment": "See http://www.chromium.org/chromium-os/developer-guide/disk-layout-format",
  "metadata":{
    "rootdev_base": "/sys/devices/platform/soc/11230000.mmc/mmc_host/mmc*/mmc*:*/block/mmcblk*"
  },
  "parent": "legacy_disk_layout.json",
  "layouts": {
    "base": [
      {
        "num": 1,
        "size": "5 GiB"
      }
    ],
    "usb": [
      {
        "num": 1,
        "size": "5 GiB"
      }
    ],
    "usb-updatable": [
      {
        "num": 1,
        "size": "5 GiB"
      }
    ],
    "factory_install": [
      {
        "num": 1,
        "size": "200 MiB"
      }
    ]
  }
}