The Intrusive Blackout
By default, Ubuntu (specifically the GNOME desktop environment) utilizes aggressive power management rules. To conserve monitor lifespan and reduce energy consumption, the system will automatically suspend the screen (blanking it to black) after a very short period of inactivity, typically 5 minutes. If you are reading a long article, monitoring a dashboard, or watching a video in a media player that fails to send a “keep-awake” signal to the display manager, the screen will abruptly go black, forcing you to wiggle the mouse to restore the image.
Keeping the Display Active
To ensure your monitor stays on indefinitely and stop Ubuntu from automatically suspending the screen during periods of physical inactivity, you must adjust the core power settings.
Click the cluster of icons in the extreme top-right corner of your screen (where the battery and network indicators are) to open the Quick Settings menu. Click the gear icon to open the main Settings application. In the left-hand navigation sidebar, click on Power (you may need to scroll down slightly). Look at the right-hand panel for the section labelled “Power Saving Options.” You will see a dropdown menu explicitly labelled Screen Blank. Click this dropdown menu. It will list several time intervals (e.g., 5 minutes, 15 minutes). Select the option at the very bottom of the list: Never. By selecting “Never,” you instruct the display server to ignore idle time completely; your screen will remain fully illuminated until you manually lock the machine or close the laptop lid.