Home > AMLogic, Android, Linux, Linux 3.0, Testing, Ubuntu > How to Extract a Device Tree File from Android Firmware Files

How to Extract a Device Tree File from Android Firmware Files

Up to now, all our cheap Android devices were based on older Linux kernel (3.0.x, 3.4.x) that still used board files (arch/arm/board, but we’ve recently seen companies like Amlogic and Rockchip release source code with Linux kernel 3.10.x. One of the key differences between these version are the move from board files to flattened device tree and multi-platform support. If it is fully implemented, a single kernel image should be able to boot multiple hardware platforms, and all low level configuration handled by the device tree file. Since I’ve connected the serial port of Tronsmart Vega S89 for debugging, and it’s a slow news day, I thought I might try to boot the Linux kernel I compiled myself, but one of the challenge was to get the device tree file. I’ll show how to extract it from the firmware. It should also be possible to get it directly from the flash, but “cat /proc/mtd” does not show a complete list of partition as in previous versions.

I’ve performed the steps below in Ubuntu 14.04. The first thing is to install some tools: the device tree compiler that we’ll use to decompile the dtb (binary) file into a dtd (text) file, and split_bootimg.pl a standard PERL script to extract files from boot.img:

I’ll use M8 / TM8 firmware (Amlogic S802) as an example. The exact procedure will vary between firmware files, but if you can boot.img, the procedure should be platform independent and work for any ARM SoC. After having downloaded and extracted the firmware file (TM8 ap6330_03102014A_0410_ROOT.rar), let’s create a working directory, and unzip the “OTA” file.

We now get a bunch of files, including boot.img. Great! Time to run split_bootimg.pl script to extract its content:

So we’ve got the kernel, a ramdisk, and a “second file” that happens to be the dtb file. We can now decompile it with dtc (device tree compiler) as follows:

That’s it. Here’s M8 device tree file.

I’ve done the same for Tronsmart Vega S89 (Elite). S89 firmware is usually distributed as an IMG file to be used with AML Flash Burning tool, but I haven’t found a way to extract such file yet. however, I’ve found an “OTA” firmware, to be updated via SD Card, on freaktab, and could extract the device tree file for Tronsmart Vega S89 Elite & Vega S89. Both M8 and S89 Elite DTD files are very similar, but the maximum CPU frequency seems to be higher in M8, and there are other apparently minor differences. Vega S89 DTD file appears to be much different however.

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  1. m][sko
    May 12th, 2014 at 22:37 | #1

    Did you finally boot up fully working kernel now?

  2. Alain Theriault
    May 13th, 2014 at 00:57 | #2

    This looks like fun… let me know how I can help.

  3. May 13th, 2014 at 09:37 | #3

    I’m loading the built boot.img via tftp and running it from there.
    Before it could boot to command line (in the ramdisk), but no Ethernet.
    With the right device tree file, I get Ethernet, and access to the command line. HDMI output seems to work but it’s all black. I was expecting the Android UI to show up as well. It’s probably because I need to modify the ramdisk. There are some pinmux conflict in the log as well, because of a camera module which is not present in the stock firmware. Expect progress to be slow, as I play on this only if I can’t find much to write about during the day.

    @Alain Theriault
    If you want to give it a try, here’s what I’m planning to do:
    1. Get console access to your M8 – Similar to http://www.cnx-software.com/2014/05/07/how-to-open-tronsmart-vega-s89-elite-and-access-the-serial-console/
    2. Build the kernel with the M8 DTD file (modify mk_m8.sh)- http://www.cnx-software.com/2014/03/10/amlogic-gpl-source-code-release-kernel-3-10-u-boot-and-drivers-wi-fi-nand-tvin-mali-gpu/ + post above
    3. Configure a tftp and nfs server in your Linux PC
    4. Copy to your boot.img to the tftp directory, and an ARM Linux rootfs to the NFS share (e.g. ALIP: http://releases.linaro.org/13.11/openembedded/vexpress-lsk/linaro-image-alip-genericarmv7a-20131126-163.rootfs.tar.gz)
    5. Try to boot with an adaptation of the following: http://forum.xbmc.org/showthread.php?tid=152328&pid=1304803#pid1304803

    If you want to make sure the kernel is working properly, you may want to boot Android instead. As mentioned to misko answer, your may need to modify the ramdisk, or just take the one from M8 firmware.

  4. gizmomelb
    May 13th, 2014 at 19:34 | #4

    hey cnxsoft, don’t know if it’s of any use – but I extracted the partitions with boot.img etc. on my Beelink 16GB (Tronsmart Standard S89 hardware-a-like) if those files are of any use to putter around in?

    I’m mostly a windows guy, I need to set up a *nix box for playing around on (mm.. maybe I could use my raspberry pi for that).

  5. Dante
    May 13th, 2014 at 19:51 | #5

    M8 is better then S89 Elite?
    Antutu benchmark? I Can’t find anything good about m8 (S802).


  6. May 13th, 2014 at 20:17 | #6

    Both are about the same. But when I tried M8 tended to hang from time to time. It could have been hardware (overheat) or firmware issue. Not sure.

    Did you get the boot.img from the NAND Flash or firmware file? If from the NAND flash, how did you do? I can’t find the partitions in my Vega S89 Elite.
    If you are a Windows guy, and want to play around, you’d better install VirtualBox + Ubuntu on your windows PC, especially if you’re going to give a try at building the kernel. The Raspberry Pi use would be limited (tftp / nfs server), hence unnecessary.

  7. gizmomelb
    May 14th, 2014 at 16:18 | #7

    hey cnxsoft – I extracted the boot.img from the NAND using adb shell and some help from Finless Bob on freaktab.


    I have the extracted files from the 100k4 NAND, I’ve since updated to 101k4 but haven’t extracted the files again (is there any point if we can unpack the firmware update?).

    I’m happy to help out in any way I can. I have two Beelink M8 round boxes, one for testing – my USB -> serial cable/adapter arrived today as I need to update my Gotek floppy emulator (another project).

  8. gizmomelb
    May 14th, 2014 at 16:20 | #8


    Hi Dante! The square S802 boxes are going by the M8 brand, however Beelink have a round (Tronsmart S89 clone essentially – same motherboard, different firmware but you can flash with the S89 firmware) S802 device which is named M8 (and another one named S82). Confusing!

  9. gizmomelb
    May 14th, 2014 at 16:21 | #9


    Hi cnxsoft – yeah I’ll go virtualbox or if I look around I can probably find an old VMDK VMware ubuntu image I was using to play around with thin client firmware from quite a few years back.

  10. May 14th, 2014 at 17:40 | #10

    Extracting from NAND is useful if you don’t have the firmware, which may happen for some low cost devies in the future with zero support. I got confused when I tried cat /proc/mtd…, but “ls /dev/block/” is what I should have done.

    Now I’m at the stage where I try to boot the rootfs (Linaro ALIP) from NFS. The usual bootargs method does not seem to work at all, so I’m trying switch_root, which sort of work until the “Connection Manager” starts, and seems to mess with the nfsroot…

  11. m][sko
    May 14th, 2014 at 19:43 | #11

    I don’t have any problem with debian 7.0 armhf rootfs with kernel 3.0 over NFS
    But it is maybe that you use initrd https://www.ibm.com/developerworks/library/l-initrd/
    As I build most amlogic modules as static as I don’t need any hotplug :)

    I didn’t use linaro(Ubuntu).

  12. m][sko
    May 14th, 2014 at 19:45 | #12

    my uboot paramters for AML8726-MX,

  13. May 14th, 2014 at 20:33 | #13

    Finally even if I can’t mount the NFS share directly with bootargs (I had to edit init with switch_root), it’s still importnt to have a proper bootargs in u-boot. So now I can mount the ALIP rootfs. The display is still black, but at least I get network, and USB mass storage support. I’ll document that tomorrow.

  14. September 17th, 2014 at 15:30 | #14

    For Rockchip (RK3288) the device tree file is located in resource.img.
    It can be extracted using kernel/resource_img script found in the Android SDK here: http://www.cnx-software.com/2014/09/02/rockchip-rk3288-android-4-4-2-sdk-and-schematics-released-for-firefly-board/ or there: http://www.cnx-software.com/2014/09/16/how-to-build-android-4-4-sdk-for-rk3288-tronsmart-orion-r28-beelink-r89/

    Syntax from kernel folder:

  15. John
    January 4th, 2015 at 07:18 | #15

    I have a problem: When run the command “split_bootimg.pl boot.img” i’m getting just kernel and ramdisk. I don’t have the second.gz file. What can i do?

  16. January 4th, 2015 at 09:23 | #16

    What’s the kernel version? If it’s less than 3.7, then there’s no device tree file.

  17. John
    January 5th, 2015 at 21:27 | #17

    Yes, my kernel version is less then 3.7. I have 3.4.5. In this what can i do to make my device tree?

  18. January 6th, 2015 at 09:36 | #18

    So there’s no device tree. Somebody needs to port the platform you use (Allwinner?) to a more recent kernel.

  19. Joel
    February 6th, 2015 at 05:11 | #19

    I am in the same situation….no boot.img-second.gz file. LG Optimus Fx3Q, Android 4.1.2, kernel version unknown (I am running a custom one, but probably less than 3.7).

    So all it takes is recompiling the kernel against a newer source? Are there any roadblocks/considerations/gremlins associated with such a task?

  20. February 6th, 2015 at 10:06 | #20

    If there’s no new port, you’d basically need to become a kernel developer,so if you have no experience that would be quite a roadblock, and even if you have that could be months of work.

    If your processor is supported in a more recent version of the kernel, you might just have to write the device tree file by yourself, but that assume all required drivers for your hardware are also part of the kernel. There may also be an issue with binary drivers (GPU. Wi-Fi), and if they don’t match your kernel version, you may be out of luck.

  21. Joel
    February 6th, 2015 at 18:48 | #21


    Would merging the kernel source with say, the Optimus F6 (a similar device, which I think has a 3.7+ kernel out there) be any easier? Or is that what you had in mind with my original question?

    I’ve compiled Linux Kernels before (the Debian way), so merging the kernel sources, although daunting, seems less of a chore than writing a device tree by hand (especially when I don’t know where to start). Sadly, although similar, the F6 tree does not work for this device (ROM won’t compile).

    Thanks for your opinion.

  22. February 6th, 2015 at 20:42 | #22

    If you have a device tree kernel for another device with the same processor, then it will help a lot, but you’ll still need to modify the device tree file yourself, and maybe some other bits too in the source code. It won’t be from scratch so most probably easier. Disclaimer: I’ve never done that myself.

  23. Jon Smirl
    February 6th, 2015 at 21:29 | #23

    Check and see if the device tree is exposed in /proc. Exposing it is a kernel option.

    Also the dtc compiler is part of the Linux kernel tree. You don’t have to build it separately.

    It is possible to append the DTB onto the end of the kernel image, in that case it is not a separate file. It is still there, just harder to get to.

    Just because these chips are on Linux 3.10 does not force them onto device tree. I have several systems here still using board files on 3.10. I really, really wish these vendors could understand the benefits of contributing code to mainline and then start doing it. A few are starting but many more aren’t.

    Hint to vendors – your pile of out of tree code that has to keep getting ported to each release is only going to growing larger and larger until it collapses and buries you. Once the code is in mainline that part of the pile will stop growing. This is nothing new and has been going on for twenty years. There are hundreds of dead companies out there that collapsed under the ever growing expense of maintaining proprietary Linux versions.

  24. Li
    March 15th, 2015 at 04:37 | #24

    I got the blog has incorrect magic number error.

    dtc -I dtb boot.img-second.gz -O dts -o meson8.dtd
    DTC: dtb->dts on file “boot.img-second.gz”
    FATAL ERROR: Blob has incorrect magic number

  25. March 15th, 2015 at 09:54 | #25

    I’m not sure why.
    FTD_MAGIC is defined in http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/scripts/dtc/libfdt/fdt.h#L44
    and checked in flatree.c @ http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/scripts/dtc/flattree.c#L808

    Maybe you could try to edit dtc source code to display the magic number you get, and work from there.

  1. May 15th, 2014 at 16:15 | #1
  2. September 16th, 2014 at 20:45 | #2