Flashing BeagleBone Black (rev B, 2GB eMMC) with Ubuntu 14.04
You're supposed to be able to use "BBB-eMMC-flasher" images to flash new OS directly from SD card. For whatever reason this sometimes fails to work. People blame power supplies which probably is one reason but not this time. In my case when trying to use BBB-eMMC-flasher image BBB started flashing all four user leds in sync without ever even attempting to flash image to eMMC.