Creating a Mac OS USB Boot Drive via CLI - macmiester/luci GitHub Wiki

This can be accomplished in a few different ways.

Use createinstallmedia explained here

Mounting your USB drive via Terminal is explained here

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Kingston\ Mac/ --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

The exact volume mount name can be determined by running: cd /Volumes and then ls