Hello Linux Geeksters. As you may know, Canonical has created a new lock screen for Ubuntu 14.04 Trusty Tahr, which looks exactly as the login screen.
If you want to get the old Ubuntu lock screen back, you have to install the compizconfig-settings-manager, like this:
$ sudo apt-get install compizconfig-settings-manager
Next, go to the Unity Dash, Open the CompizConfig Settings Manager:
And from the General Tab, go to Lockscreen and from the drop-down box choose LightDM, instead of Unity:
After this, your lock screen will look like this: