Restoring MLO and uboot to eMMC and microSD

[Luther Goh Lu Feng]

Given that the eMMC and microSD has different drive geometries[1], what is the correct way of backing up and restoring the MLO and u-boot from one medium to another? eg from eMMC to microSD or from microSD to eMMC.

--Luther

[1] https://groups.google.com/d/msg/beagleboard/4HTJt7J2M8w/3qdig-7hBQAJ

[Robert Nelson]

On Wed, Oct 18, 2017 at 2:41 PM, 'Luther Goh Lu Feng' via BeagleBoard
<beagl...@googlegroups.com> wrote:
> Given that the eMMC and microSD has different drive geometries[1], what is
> the correct way of backing up and restoring the MLO and u-boot from one
> medium to another? eg from eMMC to microSD or from microSD to eMMC.

That's incorrect, the drive geometries doesn't affect MLO/u-boot.img
which are always in the same location on either eMMC/microSD.

you can use 'dd' to extract them or just grab the "backup" versions
found under: /opt/backup/uboot/

Regards,

--
Robert Nelson
https://rcn-ee.com/

[Luther Goh Lu Feng]

From https://groups.google.com/d/msg/beagleboard/4HTJt7J2M8w/3qdig-7hBQAJ

>> Next question. If I flash the eMMC using the microSD card debian flasher 
>> script, and then dd out 1MB from the eMMC and microSD, do I expect both to 
>> have the same shasum? I expect yes, since they came from the same debian 
>> image, but unless I made a mistake or there are some false assumptions on my 
>> part, I seemed to be getting different checksums 

> No... different drive geometries.. 

Just to clarify, does the above still hold true? If yes, does it mean that different drive geometries means that the 1MB of each storage medium contains other drive specific stuff, together with the MLO and u-boot, and therefore results in differences in the 1MB content for each drive?

--Luther

[Luther Goh Lu Feng]

I have a BBB which has the eMMC flashed from the microSD card using the flasher script. Therefore, the MLO and the u-boot should be idenitical.

Referencing the eewiki page[1]I backed up the MLO from the eMMC and the microSD:

sudo dd if=/dev/mmcblk0 of=./mmcblk0_MLO count=1 seek=1 bs=128k

sudo dd if=/dev/mmcblk1 of=./mmcblk1_MLO count=1 seek=1 bs=128k

The shasums are however different:

debian@beaglebone:~$ sha256sum mmcblk0_MLO

493f8723705c73c3383898658ce2b1855bbca219825198d2a23b115ce30a4ada  mmcblk0_MLO

debian@beaglebone:~$ sha256sum mmcblk1_MLO

51d7b68ec8eac56f6d04371c77885332e9eedc7c5434350750ba58f51e86fd56  mmcblk1_MLO

Am I backing up the MLO correctly?

[1] https://eewiki.net/display/linuxonarm/BeagleBone+Black#BeagleBoneBlack-SetupmicroSDcard

[Luther Goh Lu Feng]

Bump