1) Udev doesn't do anything about separate /usr, its systemd that does. Both are in the same source tree but unrelated at runtime(i.e. udev can be used without

1) Udev doesn't do anything about separate /usr, its systemd that does. Both are in the same source tree but unrelated at runtime(i.e. udev can be used without systemd). 2) systemd only prints a warning about separate /usr, it then continues to go on as before, so it does not affect this working or not. 3) The reasons that separate /usr are broken is not because of systemd, but the other parts of the system that rely on things in /usr in early boot. This happens in a variety of cases where services or hw support code rely on binaries in /usr/bin or data in /usr/share. Nothing you change in udev or systemd can make this work better, its all about fixing the rest of the system, something nobody cared to do for the 10 years before systemd added the warning to tell people of this problem.