[BH] Issues booting from eMMC with NON-BOOTABLE SD card inserted

[drpi]

I think it's looking for u-boot somewhere in the first MB or so of the card. If you had an OS on there and just deleted everything from the partitions u-boot might still be on there. You have to overwrite everything with zeroes, i think 8k from the start to the start of the first partition.
Something along the lines of

Code:

dd if=/dev/zero of=/dev/mmcblk0 bs=8k seek=1 count=64

will probably be enough.

I had used this drive as an OS drive prior, however it never occurred to me the boot sector might still be populated.  Thanks for the reminder that unflagged is not overwritten!

Unfortunately, even after using dd it still would not boot with the SD card inserted.  I even went so far as to set the count to 128, thus overwritting the entire 1st MB of the drive, to no avail.

After digging around in a few drawers I found an SD card I was sure had not ever been set to boot (I've been testing allot of distro/revs on the pinephone...) and it booted up perfectly!

So, thanks for the help!

I've checked the drive in question on serveral OS's (linux and windows) using different partition managers and I'm not seeing anything that would cause it to appear as a bootable device.  Is there anyone else that is booting off of internal storage that would be willing to test if a formerly-bootable SD card causes the same issues I'm seeing?

The boot stub is located outside partitions.
On the SD card, the partition sector is located at sector 0.
This partition sector locates the first partition at, for example, sector 128 (can be another value).
In the gap between sector 0 and sector 128, there is a boot stub. Removing partitions has no effect on the boot stub.
You have to erase the first sectors of the SD card to remove the boot stub.