I’ve rolled out Webmin 1.853 to the Debian/Ubuntu Virtualmin 6.0 repositories. This is to address a bug on Ubuntu 16.04 where the init system is incorrectly detected as upstart (because both initctl and systemctl exist on the system, even though systemd is actually the default init system). This is a minor bugfix release, and is not needed on CentOS/RHEL systems.
It’s only in the /vm/6 repos. So, if you installed with the old installer (any version 1.x.x) rather than the new one (any version 6.0.x), you won’t find it, and won’t need it. Debian doesn’t need it anyway…I only rolled it for Ubuntu, but they share a universal repo for our packages, so debian got it, too.