I read a lot of U Boot documentation the last hours but I still fail at fundamental understanding, like:   - where can variables be set? boot.scr obviously, but there is also uEnv.txt boot.cmd armbianEnv.txt ... and in which order and precendence are they parsed? (If I set a variable in different files, which value will be used? first? last? ...) - how is a change made persistent (saveenv does not work) - Can sub-variables be changed, e.g. root in bootargs   what I am