README-environments

There are several environment text files included, these are targeted
towards the CuBox-i, but may be useful for other devices.

default.txt	Contains the default boot scripts and variables for
		the CuBox-i U-Boot.

u-boot.txt	Contains a custom boot environment with scripts and
		variables.  The following environment files pertain
		to this custom environment.

reset.txt	Resets all parameters back to default.  Same as using
		the "run reset" command in U-Boot.

videocon.txt	Set variables to use the video console with USB keyboard.
		This also affects the bootargs kernel command line.  Same
		as using "run videocon" in U-Boot.

serialcon.txt	Set variables to use the serial console.  Same as using
		"run serialcon" in U-Boot.

old_kern.txt	Set variables to use older kernel (uImage, no dtb file),
		same as using "run old_kern" in U-Boot.

new_kern.txt	Set variables to use newer kernel (zImage, dtb file), same
		as using "run new_kern" in U-Boot.  This is the default.

To use any of these, run (for example, with the serialcon.txt file):

uboot-env set < serialcon.txt

If you want to load the u-boot.txt or default.txt, you may want to clear
all other variables out:

uboot-env del -i
uboot-env set < default.txt

You can also force the default U-Boot environment by corrupting the save
area; the cleanest way to do this is to use dd to zero the area (thus
the checksum fails, and U-Boot loads default environment).  The following
command works on the CuBox-i, with an offset of 0x60000 and length of
0x2000.  VERIFY the command, be certain you're writing to the correct
device or you will lose data.

verify that U-Boot variables are installed (if this fails, either you
don't need to run the dd command, or the offset/length is WRONG so
you should NOT run the dd command):

uboot-env -o 0x60000 -l 0x2000 -d /dev/mmcblk0 del -i

If that command succeeds with no error, you can safely use:

dd if=/dev/zero bs=8K count=1 seek=48 of=/dev/mmcblk0

8K = 0x2000, 48 * 8K = 0x60000