Using SBL on UP2 Board

This document builds on the Getting started guide for UP2 board, and explains how to use SBL instead of UEFI to boot UP2 board.

Slim Bootloader is an open-source boot firmware solution, built from the ground up to be secure, lightweight, and highly optimized while leveraging robust tools and libraries from the EDK II framework. For more information about booting ACRN with SBL, please visit


We show a verified Boot Sequence with SBL on an Intel Architecture platform UP2, and the boot process proceeds as follows:

  1. SBL verifies and boots the ACRN hypervisor and Service OS kernel
  2. Service OS kernel verifies and loads ACRN Device Model and vSBL
  3. vSBL starts the User-side verified boot process


The following hardware and software are required to use SBL on an UP2 board:

  • UP2 kit (Model N3350)
  • USB 2.0 Pin Header Cable for debug UART output
  • USB to TTL Serial Cable (PL2303TA for example) for debug UART output
  • 3 Pin Male To Male Jumper Cable Dupont Wire for debug UART output
  • Micro USB OTG Cable for flashing
  • Linux host
  • Internet access

The connections between USB to TTL Serial Cable and USB 2.0 Pin Header Cable should be:


Build SBL

Follow the steps of Building and Stitching from to generate the BIOS binary file <SBL_IFWI_IMAGE>, which is the new IFWI image with SBL in BIOS region.

Flash SBL on the UP2

  1. Download the appropriate BIOS update for UP2 Board.

  2. Put the empty USB flash drive in your PC and format it as FAT32.

  3. Decompress the BIOS zip file into the formatted drive.

  4. Attach the USB disk and keyboard to the board and power it on.

  5. During boot, press F7 on the keyboard to enter the UEFI BIOS boot menu.

  6. Navigate through the following menus and select Built-in EFI shell.

  7. Please take note to which filesystem number fs* your USB drive is mapped.

  8. Switch to that filesystem, e.g. fs1:. (Don’t forget the colon.)

  9. Navigate to the path where you decompressed the update (the cd and ls commands are available here, as if in an Unix shell).

    Fpt_3.1.50.2222.efi -f <SBL_IFWI_IMAGE> -y

Build ACRN for UP2

In Clear Linux, build out the SOS and LaaG image with these two files:

$ wget
  • uos.json

An example of the configuration file uos.json:

    "DestinationType" : "virtual",
    "PartitionLayout" : [ { "disk" : "clearlinux.img", "partition" : 1, "size" : "100M", "type" : "EFI" },
                          { "disk" : "clearlinux.img", "partition" : 2, "size" : "10G", "type" : "linux" } ],
    "FilesystemTypes" : [ { "disk" : "clearlinux.img", "partition" : 1, "type" : "vfat" },
                          { "disk" : "clearlinux.img", "partition" : 2, "type" : "ext4" } ],
    "PartitionMountPoints" : [ { "disk" : "clearlinux.img", "partition" : 1, "mount" : "/boot" },
                               { "disk" : "clearlinux.img", "partition" : 2, "mount" : "/" } ],
    "Version": 31030,
    "Bundles": ["kernel-iot-lts2018", "openssh-server", "x11-server", "os-core", "os-core-update"]


To generate the image with a specified version, modify the “Version” argument, "Version": 3**** instead of "Version": 31030 for example.

Build SOS and LaaG image:

$ sudo -s
# chmod +x
# ./ --images-type all --clearlinux-version 31030 --laag-json uos.json


You must have root privileges to run

If you want to build with your own acrn-hypervisor, add the --acrn-code-path argument that specifies the directory where your acrn-hypervisor is found.

When building images, modify the --clearlinux-version argument to a specific version (such as 31030). To generate the images of SOS only, modify the --images-type argument to sos.

This step will generate the images of SOS and LaaG:

  • sos_boot.img
  • sos_rootfs.img
  • up2_laag.img

Build the binary image partition_desc.bin for GPT partitions and change the partition layout in partition_desc.ini if needed.

$ cd ~/acrn-hypervisor/doc/tutorials/doc/tutorials/
$ sudo -s
# python2 partition_desc.ini>partition_desc.bin

We still need the configuration file flash_LaaG.json for flashing, which is also in the directory ~/acrn-hypervisor/doc/tutorials/.

Filename Description
sos_boot.img This SOS image contains the ACRN hypervisor and SOS kernel.
sos_rootfs.img This is the root filesystem image for the SOS. it contains the Device Models implementation and SOS user space.
partition_desc.bin This is the binary image for GPT partitions
up2_laag.img This is the root filesystem image for the SOS. It has an integrated kernel and userspace.
flash_LaaG.json Configuration file for Intel Platform Flash Tool to flash SOS image + hypervisor/SOS boot image + SOS userland


In this step, build SOS and LaaG images in Clear Linux rather than Ubuntu.

Download and install flash tool

  1. Download Intel Platform Flash Tool Lite from
  2. For the Ubuntu host, install platformflashtoollite_5.8.9.0_linux_x86_64.deb for example.

SOS and LaaG Installation

  1. Connect a USB cable from the debug board to your Ubuntu host machine, and run the following command to verify that its USB serial port is discovered and showing under /dev.

    $ ls /dev/ttyUSB*
  2. Connect to the board via minicom, and use /dev/ttyUSB0. For example:

    $ sudo minicom -s /dev/ttyUSB0


    Verify that the minicom serial port settings are 115200 8N1 and both HW and SW flow control are turned off.

  3. When the following console log displays, press any key to enter the shell command:

    ====================Os Loader====================
    Press any key within 2 second(s) to enter the command shell
  4. Swap the boot sequence of DevType: MEM to Idx:0:

    Shell> boot
    Boot options (in HEX):
      0|      0|   MMC |    0 |   0 |    0 |  RAW |    1 | 0x0
      1|      4|   MEM |    0 |   0 |    0 |  RAW |    0 | 0x0
      s   -- swap boot order by index
      a   -- modify all boot options one by one
      q   -- quit boot option change
      idx -- modify the boot option specified by idx (0 to 0x1)
    Updated the Boot Option List
    Boot options (in HEX):
      0|      4|   MEM |    0 |   0 |    0 |  RAW |    0 | 0x0
      1|      0|   MMC |    0 |   0 |    0 |  RAW |    1 | 0x0
  5. Exit and reboot to fastboot mode:

    Shell> exit
     40E0 |  175118 ms |     158 ms | Kernel setup
     40F0 |  175144 ms |      26 ms | FSP ReadyToBoot/EndOfFirmware notify
     4100 |  175144 ms |       0 ms | TPM IndicateReadyToBoot
    Starting MB Kernel ...
     abl cmd 00: console=ttyS0,115200
     abl cmd 00 length: 20
     abl cmd 01: fw_boottime=175922
     abl cmd 01 length: 18
    boot target: 1
    Enter fastboot mode ...
    Start Send HECI Message: EndOfPost
    HECI sec_mode 00000000
    GetSeCMode successful
    GEN_END_OF_POST size is 4
    uefi_call_wrapper(SendwACK) =  0
    Group    =000000FF
    Command  =0000000C
    Result   =00000000
    RequestedActions   =00000000
    USB for fastboot transport layer selected
  6. When the UP2 board is in fastboot mode, you should be able see the device in the Platform Flash Tool. Select the file flash_LaaG.json and modify Configuration to SOS_and_LaaG. Click Start to flash to flash images.


Boot to SOS

After flashing, UP2 board will automatically reboot and boot to the ACRN hypervisor. Log in to SOS by using the following command:


Launch UOS

Run the script to launch the UOS:

$ cd ~
$ wget
$ sudo ./ -V 1

Congratulations, you are now watching the User OS booting up!