Ubuntu – Lock screen Ubuntu 16.04


I am unable to lock my screen either using CTRL-ALT-L or waiting for 5 minutes (inactive time option). After pressing the combination of keys (or waiting the 5 minutes), the screen turns off but it does not ask for any password to return to the desktop. Can anyone help me please? Thank you!

Here are my settings:

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Best Answer

I solved my problem. There was an option in the Unity Tweak Tool that was preventing any screen lock. Desktop lock checkbox must be disabled. Thanks to https://askubuntu.com/a/91719/219893

Unity tweak tool desktop lock