Hwpack

"hwpack" means a "hardware-specific package".

Latest hwpacks for various Allwinner devices are available from http://dl.linux-sunxi.org/amery/sunxi-3.0/latest/

Updating your SD-card with u-boot from a hwpack
Extract the downloaded hwpack file: tar -xf *_hwpack.tar.xz

You will get 3 directories:
 * bootloader: contains u-boot;
 * kernel: contains uImage and script.bin for the boot partition;
 * rootfs: contains some configuration files and kernel modules to be copied into your root partition.

u-boot consists of two files (sunxi-spl.bin and u-boot.bin) in the bootloader directory.

You will need to write them into fixed areas of your SD-card: dd if=sunxi-spl.bin of=/dev/sdX bs=1024 seek=8 dd if=u-boot.bin of=/dev/sdX bs=1024 seek=32 ...where /dev/sdX is your SD card (make sure you use the correct device name here).