If you are watching a movie on your laptop or are reading any PDF material, etc then you might have noticed that the system’s display turns off if no action is taken in a particular period of time. Let me show you an easy way to disable this system setting in Ubuntu.
There are some changes that need to be made in the Power Management section, first go to the Power Management settings from System > Preferences > Power Management. The Power Management Preferences will be displayed, here you will see the Put display to sleep when inactive for: option, under the Display heading, now please move the slider which is given next to this option, to the right.
Now if you have the screensaver activated, then make sure to deactivate it. In order to do this, go to System > Preferences > Screensaver, and uncheck the two checkboxes Activate the screensaver when computer is idle and Lock screen when screensaver is active.
You are done.