comments, output
update-rc.d $display_manager remove as dpkg post invoke hook,
otherwise as soon as a display manager (kdm by default) get upgraded,
its postinst script will revert Whonix's post chroot script and Whonix's
feature, which deactivated the /etc/init.d/ autostart mechanism,
what would break Whonix's feature to decide to start a display manager
depending on free RAM and other configurable settings