How to Write an Image to the eMMC Module Tutorial

[MarkHaysHarris777]

Why installation is not done by just like this:
1) insert an SD card card with the "minimal" linux.
2) snap an empty eMMC in
3) turn the board on, boot from SD
4) download an image and flash it into eMMC by that smartass script.

I know it's obvious and hardly nobody could think of it before, rather there are some obstacles to do so. What they are?

Hi, the reason your simplified approach will not work is that boot precedence and eMMC initialization create two problems which prevent it.  If there is an image on the eMMC already, then the eMMC will boot 'first'.  If there is no image on the eMMC then either the machine will not boot, or if it does boot,  both devices will not be 'seen' by the OS during initialization; both mmcblk0 and mmcblk1 must be present, AND the machine has to be booted from SD.

The jumper used has one function,  it grounds the clock line of the eMMC, deactivating it temporarily;  that way the SD card will boot-up because (for all intents and purposes) the eMMC is not there.  We interrupt the boot-up at the uboot timer and then continue the bootup with the jumper removed--  this allows the boot-up to continue on SD, but also allows the OS to 'see' the eMMC module during initialization.

Thanks for the question.