Flashing BBB eMMC with Yocto Image?

Salutations fellow BeagleBoard members,

Hoping to get some clarity on a question one of my students recently asked on how one would go about flashing the eMMC of the Beagle Bone Black using a Yocto image flashed on a microSD card?

Holding the microSD button labeled “S2” on power up simply boots the beagle from the microSD card and does not flash the internal eMMC, as some of the Debian images do. Powering on the beagle with the microSD card inserted without holding “S2” boots the default internal eMMC Debian image. Thoughts?

“S2” is just a boot ‘selector’… it’s up-to the image located on the microSD to “flash” the eMMC…


Thank you Robert for the clarification of the S2 selector function. Since this is a Yocto image, and not a Debian “flasher” image, what is the process to flash the eMMC with this image?

Boot into microSD and just dd the yocto image…

Any specific documentation which outlines this?

Well what do the Yocto documentation say about the microSD card?


Not sure if there is any regarding flashing to BBB. But lets say they boot from the microSD card containing the Yocto image. What are the commands needed to flash the eMMC specifically?

Hi @danjones the reason i asked you for what Yocto directions are for creating the microSD. Is that, you’d just swap the device name from what they said too… “/dev/mmcblk1”… (While booted from the Yocto microSD on the BeagleBone Black.)


Are there step by step guides on how to do this Robert? Students will need some direction. Ty


I have been working on Yocto images. Not so plain Jane. I tried w/ the yocto-beaglebone machine in the config file. This works mostly. I have four non-zero errors.

I did it wrong too. So, I was surprised that it built so well.


P.S. Oh…I tried w/ kirkstone. I am still trying. So, if I accumulate the data for the build, I will reply again. Oh and about the rootfs and boot partitions. Some people use dd and some people use other ideas like cfdisk or other ways to create partitions.

Hey there Seth! Thanks for the info. Whichever way works please list the steps. Again, the students are just trying to make the Beagle boot from eMMC flashed with the Yocto image instead of booting from the sd card, which works as expected.

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I misunderstood what was going on. I thought you were working on making the images bootable in general.

Okay…I will try. My Yocto build seems to be faulty right now (I erased the whole thing). Something was up.


P.S. I will do my best to report back for eMMC instructions only.

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Yep, we have a YOCTO image flashed to an SD card that the beagle’s are currently booting from. We simply want that image flashed to the internal eMMC so that it doesn’t need the SD card to boot.

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So, what directions did you use to create that YOCTO image? Once you boot with Yocto on the microSD, just use those exact same directions but with “/dev/mmcblk1” instead…


Yocto image was already pre-built and flashed to the sd card using balena Etcher

This image you flashed with balena Etcher, is it an img, wic, etc file?

aka, what was the file name? :wink:



Boot with microSD, copy *.img to BeagleBone Running Yocto and run as root:

dd if=<file>.img of=/dev/mmcblk1

Power Off, remove microSD, enjoy BBB with eMMC booting Yocto…


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Thanks for the guidance, Robert. So, once it boots on the SD card, copy the .img into the BBB before running the dd command above?

Or even before, not sure if Yocto resizes the disk on first bootup or not, so it might not fit on first bootup…

Or use a usb-flash drive with it in the file system.