Simply fire up your terminal and run
As macOS manual explains, this tool will
prevent the system from sleeping on behalf of a utility. I’ve used
-dimus parameters, here’s their meaning:
-d Create an assertion to prevent the display from sleeping. -i Create an assertion to prevent the system from idle sleeping. -m Create an assertion to prevent the disk from idle sleeping. -u Create an assertion to declare that user is active. If the display is off, this option turns the display on and prevents the display from going into idle sleep. If a timeout is not specified with '-t' option, then this assertion is taken with a default of 5 second timeout. -s Create an assertion to prevent the system from sleeping. This assertion is valid only when system is running on AC power.