Right now I have an SD card with Manjaro. If I disable eMMC and press reset, the power led goes red and then pinebook boots to Manjaro from SD. If I enable eMMC and press reset, power led goes off and nothing happens. I did check that eMMC is properly connected. What else can I try?
I've got me an A-A USB cable to try the recovery process but failed to do that (probably didn't do the sequence right). Instead I tried again to boot with eMMC disabled and enable it once the boot started. I've stopped the U-boot from automatically booting and it showed that eMMC does indeed exist. After that I booted into Linux and did `dd if=/dev/mmcblk1 of=/dev/mmcblk2` (from SD card to eMMC). Rebooted again and it booted from eMMC.
That's good
Really, all you needed to do was copy mbr (1 sector) to sd, dd 1st 16M sd->emmc, restore emmc mbr
If it should be a little 'flakey' a non-booted distro has the /dev, /sys, /proc, /run
directories empty, just the top directories and the kernel fills them with virtual files
So, you may have to boot from sd, mount emmc and empty those directories
I've found mc (as root) the quickest and least hassle