Now that logind will clean up all IPC resources of a user we should
really consider $XDG_RUNTIME_DIR as just another kind of IPC with the
same life-cycle logic as the other IPC resources. This should be safe
now to do since every user gets his own $XDG_RUNTIME_DIR tmpfs instance
with a fixed size limit, so that flooding of it will more effectively be
averted.
# See tmpfiles.d(5) for details
-d /run/user 0755 root root ~10d
+d /run/user 0755 root root -
F! /run/utmp 0664 root utmp -
d /run/systemd/ask-password 0755 root root -