Troubleshoot your dead screen in Ubuntu with LightDM.

This works great in times when you lose your user interface and reach a dead-end. In order to troubleshoot your black screen you need to go through the following steps:

  1. Open a Virtual Console

virtual console (VC) – also known as a virtual terminal (VT) – is a conceptual combination of the keyboard and display for a computer user interface. It is a feature of some operating systems such as BSDLinux, and UnixWare in which the system console of the computer can be used to switch between multiple virtual consoles to access unrelated user interfaces. Virtual consoles date back at least to Xenix in the 1980s. The Keyboard Combination to open Virtual Terminal is CTRL + ALT + F1. You can even use F2 to F6, but remember F7 is your recent console.

2. Run LightDM from the terminal

LightDM is an X display manager that aims to be lightweight, fast, extensible and multidesktop. It uses various front-ends to draw login interfaces, so-called Greeters.   I understand that lightdm is the display manager like explorer.exe manages window’s display. So a dead screen appears means your lightdm is off. Run it typing: sudo lightdm start in your terminal and you are into your interface.  

NOTE: Definitions are referenced from wikipedia