The keyboard shortcut is trying to use xscreensaver which is not installed and should be using lxlock.
~/.config/openbox/lubuntu-rc.xml Currently: <!-- Lock the screen on Ctrl + Alt + l--> <keybind key="C-A-l"> <action name="Execute"> <command>xscreensaver-command -lock</command> </action> </keybind> Change to: <!-- Lock the screen on Ctrl + Alt + l--> <keybind key="C-A-l"> <action name="Execute"> <command>lxlock</command> </action> </keybind> ** Changed in: lxsession (Ubuntu) Status: New => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1273077 Title: Crtl+Shift+L fails to lock session To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lxsession/+bug/1273077/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs