I am running Ubuntu from a live session in order to see if I can reproduce this bug. Since though I'm still supposed to get stuff done, I'm trying to also do that. As a result I have to log onto corporate resources, and lock my screen while I'm not at my desktop.

I set a password on the default ubuntu/999 user account, but Ctrl-Alt-L still does not lock the screen, it merely blacks out the monitor.

How can I have a proper screen lock? Maybe I should just install xscreensaver...

  • I feel that the fact that I happened to be running Ubuntu+1 here is in no way relevant to the question, or the answer I have provided, since all supported versions of Ubuntu are equally incompatible with xscreensaver. – badp Feb 25 '16 at 16:04
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    @DnrDevil That's true, however the issue is also present in Ubuntu 14.04 and Ubuntu GNOME 15.10, so it's not specific to Xenial or due to a bug, it's just how the Live session works. – kos Feb 25 '16 at 16:23

On Ubuntu 12.04 & above with Unity/GNOME, you can enable locking the screen with the following command:

gsettings set org.gnome.desktop.lockdown disable-lock-screen false

However without a password it may not even work or be able to login i would recommend adding a user as well first just in case.

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  • Also under System SettingsSecurity & PrivacySecurityRequire my password when, check Returning from blank screen – badp Feb 25 '16 at 16:20
  • Answer still relevant for Ubuntu 18.10 LiveUSB. Enable automatic lock when screen turn off in Settings > Privacy > Screen lock. Don't forget to set a password, also in Settings > Details > Users > Password – solsTiCe Nov 9 '18 at 21:31

Probably not optimal, but it worked.

  1. Set up a password from the terminal (the graphical interface didn't work for me, but ymmv).

  2. Open Software & Updates and enable all repositories.

  3. Install xscreensaver.

    sudo apt-get update
    sudo apt-get install xscreensaver
  4. Launch the xscreensaver demon. This also opens up a window.

  5. Click on Settings and tick Lock Screen After. Set your timeout.

  6. Open System SettingsKeyboardShortcuts, and add this shortcut:

    xscreensaver-command -lock

    Assign to it the key combination of your choice; it's fine to override ctrl-alt-l.

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