U-Boot/Legacy U-Boot

Initially developed by Tom Cubie and now developed and maintained by Henrik Nordström the u-boot support comes in two branches, one with NAND and android stuff(boot.img, fastboot) support and another with MMC-only ( aka SD ) support, which is more the traditional linux style.

For details see the linux-sunxi u-boot wiki.

Tutorials
How to remove the old environment from a card:  card=/dev/sdc #/dev/mmcblk0 dd if=/dev/zero of=${card} bs=1024 seek=544 count=128

u-boot nand enviroment
Example u-boot enviroment from a stock android u-boot enviroment partition bootdelay=0 bootcmd=run setargs boot_normal console=ttyS0,115200 nand_root=/dev/nandc mmc_root=/dev/mmcblk0p4 init=/initloglevel=8 setargs=setenv bootargs console=${console} root=${nand_root} init=${init} loglevel=${loglevel} boot_normal=nand read 40007800 boot;boota 40007800 boot_recovery=nand read 40007800 recovery;boota 40007800 boot_fastboot=fastboot