This article explains how to create a bootable USB installer for OS X El Capitan (10.11) using Terminal on Mac.
Download the El Capitan installer from the Apple website. It is no longer available in the App Store. Once the download is complete, the installer will automatically launch. When it does, close the installer. You will need a copy of the El Capitan installer to create a bootable USB.
The El Capitan installer will be downloaded to your /Applications folder, with the filename "Install OS X El Capitan." If you have installed El Capitan and want to create a bootable installer, download the installer again from Apple.
Follow these steps to create a bootable USB installer of El Capitan in Terminal.