Choosing boot from SD or USB

WORK IN PROGESS

Those scripts should allow to boot from SD or USB by renaming files on /boot on the SD card.

Install those 2 scripts on both USB and SD card.

This have been tested on RPI 2 and 3.

How to use

Boot normally from SD
Run sudo boot_from_usb.sh
The Pi should reboot and start from USB device
Once booted from USB, you can mount the SD card and do what ever you need (backuping the SD card as an img file for instance)
Run sudo boot_from_sd.sh
The Pi should reboot on the SD card (if you did not mess too much with it...)