[Xenial][udev] postinst script should use "invoke-rc.d stop" instead of "systemctl stop"

[Guillaume Penin]

In order to respect the local initscript policy layer that may be present in /usr/sbin/policy-rc.d, the postinst script of the udev package should use "invoke-rc.d stop" instead of "systemctl stop".

This direct systemctl call can be found in the handle_service_rename() function :

handle_service_rename() {
  if dpkg --compare-versions "$2" lt "204-1"; then
    if [ -d /run/systemd/system ]; then
      systemctl stop udev.service udev-control.socket udev-kernel.socket >/dev/null 2>&1 || true
    fi
  fi
}

Using "systemctl stop" during unattended-upgrades in shutdown mode hangs and leaves the dpkg database in a broken state after reboot. Using a local initscript policy layer that prevents start/stop/restart actions on this case is a way to prevent those hangs but maintainer scripts have to use invoke-rc.d instead of direct systemctl calls.

[Dan Streetman (ddstreet)]

please reopen if this is still an issue