+* sd-resolve: add callback api
+
+* ImmutableSystem=yes/no or so to mount /usr, /boot read-only/invisible, and leave /var and /etc writable
+
+* InaccessibleHome=yes/no or so to hide /home and /run/user from a service
+
+* Run most system services with cgroupfs read-only and procfs with a more secure mode
+