EDF Disk Image Layout

This page is the canonical reference for the partition layout of the EDF Linux common disk image (edf-linux-disk-image, edf-platform-disk-image, and the Kria variants). It documents the partition map produced by the Yocto Project wic image generation, the role of each partition, mount points, filesystem types, and sizes.

Other pages in this documentation that show partition output or describe the layout cross-reference this page rather than duplicate the content.

Overview

The EDF disk image is produced by the Yocto Project from a wic kickstart file in meta-amd-edf/wic/. The kickstart used for your board, and the resulting partition layout, depend on whether the machine config sets efi in COMBINED_FEATURES.

Your board uses edf-disk-single-rootfs-efi.wks: a GPT-hybrid layout that boots through EFI with systemd-boot.

Your board uses edf-disk-single-rootfs.wks: an MBR layout that boots through U-Boot distro_bootcmd and boot.scr.

Both kickstarts produce three partitions with the same conceptual roles; only the partition table format and the first-partition contents differ. Use the board selector at the top of the page to switch the rest of this page between the two layouts.

Partition Layout

The EFI boot layout uses a GPT-hybrid partition table.

Num	Mount point	Size	Filesystem	Role	Purpose
1	/efi	1 GiB	vfat (FAT32)	EFI System Partition (ESP)	Holds systemd-boot, the Linux kernel image, loader/entries/*.conf, Xen artifacts, and UEFI capsule update files.
2	/storage	2 GiB	vfat (FAT32)	User-writable storage	Mounted with defaults,gid=100,umask=0002. Holds application data and artifacts that must survive a rootfs re-image.
3	/ (root)	grown to fill disk	ext4	Linux rootfs	General-purpose Linux user-space rootfs built by the Yocto Project. systemd-repart grows the partition and filesystem on first boot to fill the remaining disk space.

The wks selects the table format with bootloader --ptable gpt-hybrid. The ESP is marked active, and the partition-type GPT GUIDs come from ESP_PART_TYPE and ROOTFS_PART_TYPE. These follow the Discoverable Partitions Specification and are set in meta-amd-edf/conf/distro/amd-edf.conf.

On a booted EDF system the ESP contains:

/efi/
├── BOOTAA64.EFI            # systemd-boot loader (EFI default)
├── boot.bin                # SoC first-stage boot image (added post-build)
├── Image                   # Linux kernel image
├── xen.efi                 # Xen hypervisor (EDF Xen menu entry)
├── xen.cfg                 # Xen command line
├── EFI/
│   └── UpdateCapsule/      # UEFI capsule update drop directory
└── loader/
    ├── loader.conf         # systemd-boot defaults
    └── entries/
        ├── edf-linux.conf  # default Linux entry
        └── edf-xen.conf    # Xen Dom0 entry

Each menu entry’s kernel command line lives in the matching loader/entries/*.conf file. See systemd-boot for boot manager details and Root Partition Identification (PARTUUID) for the root partition identification scheme.

The distroboot layout uses an MBR partition table and applies when efi is not in COMBINED_FEATURES.

Num	Mount point	Size	Filesystem	Role	Purpose
1	/efi	1 GiB	vfat (FAT32)	First-vfat boot placeholder	Marked active and not used for EFI boot; mirrors the EFI layout for consistent partition numbering and can hold BOOT.bin on platforms whose ROM boots from the first vfat partition. The bootimg-partition source populates it from the IMAGE_BOOT_FILES machine variable.
2	/storage	2 GiB	vfat (FAT32)	User-writable storage	Mounted with defaults,gid=100,umask=0002. Holds application data and artifacts that must survive a rootfs re-image.
3	/ (root)	grown to fill disk	ext4	Linux rootfs	General-purpose Linux user-space rootfs built by the Yocto Project. systemd-repart grows the partition and filesystem on first boot to fill the remaining disk space. U-Boot distro_bootcmd scans each boot target for boot.scr to start it.

Root Partition Identification (PARTUUID)

EDF identifies the root filesystem with root=PARTUUID=... on the kernel command line rather than a device path such as /dev/mmcblk0p3. This makes the same image bootable from any media (SD, USB, UFS).

Warning

Booting two media that share the same root filesystem PARTUUID produces undefined behavior. U-Boot and Linux can enumerate the devices in different orders, and the kernel mounts the first partition with the matching PARTUUID. The PARTUUID is generated per build, so different builds on different media coexist correctly; identical copies of the same build still collide.

The wks sets the PARTUUID with --uuid="${ROOTFS_PART_UUID}" on the rootfs partition.

systemd-boot reads the PARTUUID from the loader/entries/edf-linux.conf options line.

U-Boot distro_bootcmd passes the PARTUUID on the kernel command line built by boot.scr.

Inspecting and Modifying the wic Image

List the partitions of a wic image:

$ wic ls tmp/deploy/images/<machine>/edf-linux-disk-image-<machine>.rootfs.wic
Num     Start        End          Size      Fstype
 1         32768   1073774591   1073741824  fat32
 2    1073774592   3221258239   2147483648  fat32
 3    3221258240   8589967359   5368709120  ext4

List the contents of an individual partition (here the ESP):

$ wic ls tmp/deploy/images/<machine>/edf-linux-disk-image-<machine>.rootfs.wic:1

Copy boot.bin into the ESP of an existing wic image (for SD/USB single-stage boot):

$ wic cp tmp/deploy/images/<bootbin-machine>/boot.bin \
     tmp/deploy/images/<common-machine>/edf-linux-disk-image-<common-machine>.rootfs.wic:1

Note

For the UFS image variant (.wic.ufs) the underlying device uses 4 KiB sectors, so wic cp requires --sector-size 4096:

$ wic cp --sector-size 4096 boot.bin <image-name>.rootfs.wic.ufs:1

To edit the kernel command line in a built image, copy loader/entries/edf-linux.conf out of the ESP, edit it, then copy it back:

$ wic cp <image>.wic:1/loader/entries/edf-linux.conf .
$ # edit edf-linux.conf
$ wic cp edf-linux.conf <image>.wic:1/loader/entries/

Flash Memory Layouts

The QSPI and OSPI boot flash partition tables (used for two-stage boot on Versal evaluation boards) are documented separately from the disk image layout. See OSPI/QSPI Memory Layout - Common Specification for the common OSPI / QSPI memory map and UEFI Variables SPI Partition Layout (AMD Versal OSPI / QSPI) for the UEFI variables partition layout.