Beaglebone Black make SD card system burn write EMMC

My Beaglebone black before installing the Ubuntu 14.04 System, the use of the process found in the Ubuntu system under the serial device TTYS1~TTYS5 can not be used, open the serial port will show input/output error, I guess there may be no driver or any other reason, younger brother compared vegetables, so did not find the reason, also did not solve.
My solution is to brush back to the factory is the operating system Debian, to the Beaglebone website, the latest version of the current is 8.4. Download the system.
As for how to burn the system image to the SD card, there are many tutorials on the internet, here is a reference to the author of the article to express thanks. Http://www.cnblogs.com/daxueba-ITdaren/p/5319709.html
But if you download the system is not EMMC flask version, is Jessie for Beaglebone via MicroSD card version of the system, directly as described in the above article is no way to burn write to eMMC. You will find that no matter how you press the boot key to power on, the system will boot the SD card directly from the SD card.
When you need to boot the system from the SD card, modify the file/boot/uenv.txt in the system, find the #cmdline=init=/opt/scripts/tools/emmc/init-emmc-flasher-v3.sh, and then delete the previous # Note, at this time in the press the boot key to power up, until you see four LED lights running light, began to burn write system, and so on, the system will automatically power off, at this point is done.