Can't saveenv

I can’t saveenv.

I got this:
U-Boot# saveenv
Saving Environment to NAND…
Erasing NAND…
Attempt to erase non block-aligned data

I am not an expert in this, but if this is a Beaglebone, I don't think there is any NAND, so saveenv will not work. I think modifications to environment go in uEnv.txt or must be compiled into U-Boot.