I hope that you're aware that when booting from SD card you can simply replace kernel.img and SYSTEM using your computer instead of tedious toothpick-install-reboot process?
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Edit: If you have original firmware on NAND, you can also make a backup in OpenELEC. For example, to backup kernel and recovery:
dd if=/dev/boot | gzip > /storage/downloads/boot.img.gz dd if=/dev/recovery | gzip > /storage/downloads/recovery.img.gz
dd if=/dev/bootloader | gzip > /storage/downloads/bootloader.img.gz dd if=/dev/env | gzip > /storage/downloads/env.img.gz dd if=/dev/nand_env | gzip > /storage/downloads/nand_env.img.gz
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