Nothing you'be talked about sounds like a remotely normal thing that is documented or discussed anywhere and I doubt there's more than a fistful of orgs on the

Nothing you'be talked about sounds like a remotely normal thing that is documented or discussed anywhere and I doubt there's more than a fistful of orgs on the planet that have jury rigged that up. Meanwhile there are at least a dozen distros doing atomic image upgrades. Fedora SilverBlue for one example. These upgrades often involve a kexec restart. For fleets of servers- the target audience- it's expected that machines will go down & rolling restarts should be fine. That's how true atomic behavior is gotten. But I think you are nitpicking & being fussy with your complaining about old processes being left around; even if you do an in-place swap, but have some old processes around, at least the whole system is together & consistent. More broadly, thjs set of problem in general doesnt change much whether you are using a merged /usr or not. I genuinely dont get any of your disgust at having a /usr image that contains the functioning system image. You talk about chroots, as though it's an alternative somehow, but this practice of having a self-contained image seems like it would greatly assist in quickly cloning new images to chroot into.