I can found alot of explanation about how to burn image to eMMC storage. It’s ok.
But i want to backup the eMMC storage now. I want to create an image of the eMMC but i can’t do that from a linux stored on the sd card beacause the Banana always boot from the eMMC. So i tried to make an image directly from the armbian installed in the eMMC with the command :
The SoC might always run u-boot from eMMC if it exists, but u-boot (at least, upstream versions) will check for bootable files on SD/USB before booting a kernel from eMMC. So an SD card with the right boot files and a distro will boot u-boot from eMMC, but run the distro from SD; and from there you can simply backup or restore the eMMC using dd because the distro doesn’t see eMMC as “in use” at all. I’ve used this approach with LibreELEC images for some years now.