Searching for the MLO file on the Beaglebone Black

Newer images put MLO outside the filesystems, directly at several "magic" offsets on the eMMC/SD-card. That's documented in the TRM for AM335x.

If you don't care about current eMMC contents, something like this will do the brute force job:

dd if=/dev/zero of=/dev/mmcblk0 bs=1M count=1
(make sure mmcblk0 is the eMMC, not the SD card, it changes if you boot from SD and can be mmcblk1 too)

It wipes out the first Megabyte of the eMMC with zeroes. So the partition table and other things are gone too. Essentially you get a blank eMMC.

If you want to be a bit more surgical, look at the flashing script in /opt/scripts. Also functions.sh is interesting.

Note that MLO is also referred to as SPL.