build_library/disk_layout_anthos.json

{
  # See README_disk_layout
  "parent": "common_disk_layout.json",

  "metadata": {
    "block_size": 512,
    "fs_block_size": 4096,
    "fs_align": "2 MiB"
  },
  "layouts": {
    # common is the standard layout template.
    "common": [
      {
        # Reserve space for RW firmware. Not used on modern boards.
        # BIOS Boot Partition for COS.
        "num": 11,
        "label": "RWFW",
        "type": "firmware",
        "size": "8 MiB"
      },
      {
        # Unused partition, reserved for software slot C.
        "num": 6,
        "label": "KERN-C",
        "type": "kernel"
      },
      {
        # Unused partition, reserved for software slot C.
        "num": 7,
        "label": "ROOT-C",
        "type": "rootfs"
      },
      {
        # Unused partition, reserved for future changes.
        "num": 9,
        "type": "reserved",
        "label": "reserved"
      },
      {
        # Unused partition, reserved for future changes.
        "num": 10,
        "type": "reserved",
        "label": "reserved"
      },
      {
        # Kernel for Slot A, no file system.
        # Not used by COS.
        "num": 2,
        "label": "KERN-A",
        "type": "kernel",
        "size": "16 MiB"
      },
      {
        # Kernel for Slot B, no file system.
        # Not used by COS.
        "num": 4,
        "label": "KERN-B",
        "type": "kernel",
        "size": "16 MiB"
      },
      {
        # Board specific files, OEM partition for COS/Anthos.
        # Used for installing application binaries like Anthos.
        "num": 8,
        "label": "OEM",
        "type": "data",
        "fs_format": "ext4",
        "size": "2048 MiB",
        "uuid": "random"
      },
      {
        # Used for Legacy Bios, and EFI Bios, not ChromeOS hardware
        "num": 12,
        "label": "EFI-SYSTEM",
        "type": "efi",
        "fs_format": "vfat",
        "size": "64 MiB",
        "uuid": "clear"
      },
      {
        # Slot B rootfs. Must match Root A in side for normal
        # updates. Will contain copy of Root A after install, and
        # contain new rootfs's after runtime updates.
        # Shrink to 16 MiB since we disable update-engine.
        "num": 5,
        "label": "ROOT-B",
        "type": "rootfs",
        "size": "16 MiB"
      },
      {
        # Slot A rootfs. Rootfs + extras (AKA verity) must fit, AKA:
        #   size <= FS size + Verity size
        #
        # Verity's size can be found by:
        #   verity_bytes = div_round_up(fs_bytes, 128) +
        #                  div_round_up(fs_bytes, 16384) + 4096
        #
        # That means that the FS MiB should be:
        #   ((total_MiB * 1024 * 1024 - 4096) * 16384 / 16513) / (1024 * 1024)
        #
        # The reason to not set your fs_size to be exactly what is specified
        # by the formula above is to make builds start failing a little bit
        # before we're truly out of space, allowing a quick release valve to
        # relieve some of the pressure while we try to find other ways to save
        # space.
        #
        # Note that in the past it was observed that updates would fail if the
        # rootfs size shrunk (crbug.com/192136).  There are no known reasons to
        # shrink the rootfs size, but if you come up with one you should
        # revisit that bug and make sure it won't affect you.
        #
        # Changes to the offset of this partition may require
        # changes in cros-signing/security_test_baselines/
        # ensure_secure_kernelparams.config to allow secure boot.
        "num": 3,
        "label": "ROOT-A",
        "type": "rootfs",
        "fs_format": "ext2",
        "fs_options": {
          "squashfs": "-noI -comp lzo -Xalgorithm lzo1x_999 -Xcompression-level 9",
          "btrfs": "skinny-metadata"
        },
        "size": "2048 MiB",
        "fs_size": "2000 MiB",
        "uuid": "clear"
      },
      {
        # User data, stateful partition.
        # User data, fills all remaining space on drive.
        "num": 1,
        "label": "STATE",
        "type": "data",
        "fs_format": "ext4",
        "fs_options": {
          # A consequence of this option is that some file system
          # structures are initialized lazily when resizing,
          # resulting in much faster resize2fs invocations.
          "ext4": "-O metadata_csum"
         },
        "size": "5000 MiB",
        "features": ["expand"],
        "uuid": "random"
      }
    ],
    # Used for installs on main device
    # by default, same as 'common'.
    "base": [
    ],
    # Used for bootable USB installs (not recovery).
    "usb": [
      {
        # Slot B rootfs, unused on USB, but pad to 2M.
        # installation will expand this to size from base.
        "num": 5,
        "size": "2 MiB"
      }
    ],
    # Used for factory install images.
    "factory_install": [
      {
        "num": 12,
        "size": "32 MiB"
      },
      {
        "num": 5,
        "size": "2 MiB"
      },
      {
        "num": 3,
        "size": "420 MiB",
        "fs_size": "400 MiB"
      },
      {
        "num": 1,
        "size": "140 MiB"
      }
    ],
    # Used for recovery images.
    "recovery": [
      {
        # Slot B rootfs, unused on USB, but pad to 2M.
        # installation will expand this to size from base.
        "num": 5,
        "size": "2 MiB"
      },
      {
        # Stateful on recovery is dynamically resized larger.
        "num": 1,
        "size": "2 MiB"
      }
    ],
    # Larger rootfs, suitable for development with symbols, etc.
    # Cannot apply updates when running from USB (no slot B).
    "2gb-rootfs": [
      {
        # Will be grown to size from base on install.
        "num": 5,
        "size": "2 MiB"
      },
      {
        # Will be shrunk to size from base on install.
        "num": 3,
        "size": "2048 MiB",
        "fs_size": "2000 MiB"
      }
    ],
    # Larger rootfs, suitable for development with symbols, etc.
    # CAN apply updates when running from USB.
    "2gb-rootfs-updatable": [
      {
        # The partition size matches base, so it's installable.
        "num": 5,
        "size": "2048 MiB"
      },
      {
        # The partition size matches base, so it's installable.
        "num": 3,
        "size": "2048 MiB",
        "fs_size": "2000 MiB"
      },
      {
        "num": 1,
        "size": "4096 MiB"
      }
    ],
    # Very large rootfs, suitable for development with symbols,
    # etc. Cannot apply updates when running from USB (no slot B)
    "4gb-rootfs": [
      {
        "num": 5,
        "size": "2 MiB"
      },
      {
        # This partition is larger than the base partition, so the
        # installer will corrupt the disk during installation.
        "num": 3,
        "size": "4096 MiB",
        "fs_size": "4000 MiB"
      }
    ],
    # Huge rootfs, suitable for VM only images, should not be used
    # for actual hardware devices.
    "16gb-rootfs": [
      {
        "num": 5,
        "size": "2 MiB"
      },
      {
        "num": 3,
        "size": "16384 MiB",
        "fs_size": "16000 MiB"
      }
    ]
  }
}