If you did it before and after every system alteration, I'd count that. That's tedious and error-prone to do by hand, though, so you'd want a set of tools to do

If you did it before and after every system alteration, I'd count that. That's tedious and error-prone to do by hand, though, so you'd want a set of tools to do it automatically. At which point you've invented a new immutable distro.