I'm using Ubuntu 16.04 (updated from Ubuntu 14.04, which maby was updated from previous version, I'm not sure).
When I try to lock the screen, it gets blank an after I move the mouse the desktop shows up without asking for password. This started while I was on 14.04.
In "System Settings" > "Brightness & Lock" I have:
  Lock: on
  Lock screen after: Screen turns off
  Require my password when waking from suspend: checked
In "System Settings" > "Security & Privacy" > tab "Security" I have:
  Require my password when:
    Waking from suspend: checked
    Returning from blank screen: checked
      if screen has been blank for: 0 seconds (lock immediately)

I tried to lock the screen from the main menu > "Lock/Switch Account..." and using Ctrl+Alt+L. Both make the screen blank and after that if I move the mouse the desktop just shows (the blank screen just disapears) without asking for password. It's like locking is not working.
If I leave the computer, the display dims and after that if I move the mouse - the desktop shows without asking for password. All that worked a year ago (or something like that).

Something interesting. I made a new user. When I login with it and press Ctrl+Alt+L or use "Lock/Switch Account..." it works - the standart ubuntu login screen shows up.

Can someone help?


I recently experienced a similar issue. The only action I found to permanently resolve the matter was to reinstall 16.04 from a boot-able USB.

Step by step directions for this process can be found here: Reinstall Ubuntu with USB

  • Thank you for your reply, but this will be the last resort. I'm searching for specific fix. Aug 11 '17 at 8:42

In ubuntu 17, you need to install the "Brightness and lock" app. To find it, go to your"show applications", search for "lock", and it should pop up for your to install.

  • My version is 16.04. This solution might help, but I've already reinstalled and the problem is gone. Maybe this can help someone else with the same issue. Thank you! Apr 4 '18 at 7:57

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