I have the same problem using XFCE on Ubuntu 17.10. But Markus's solution does fix the problem.
My setup is as follows: In XFCE Power Manager under the security tab set: Automatically lock the session to "Never" Uncheck "Lock the screen when the system is going for sleep". Under the display tab I still blank the screen after 15 minutes. Put to sleep and Switch off times appear to be disabled (greyed out). Under the system tab I still have system sleep mode going to "Suspend" after an hour. Interestingly the screen still locks when it suspends. So everything still works fine and as I want it to. I get a full screen white on black message when I activate the machine again telling me the screen is locked and to wait a few seconds for a dialog box to appear. Haven't seen that before but fine nonetheless. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1605189 Title: Authentication is required for suspending the system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1605189/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
