What You Need
First, you need the OS X or macOS installer on your Mac. Ideally, download the installer, but don’t use it. When you download and use the OS X or macOS installer, the installer deletes itself as part of the installation process. If you’ve already installed OS X or macOS, redownload the installer. After it is downloaded, the installer resides in the Applications folder. It is called “Install OS X [your version]” or “Install macOS [your version].” You’ll also need a USB flash drive. Make sure that it has at least 12 GB of available storage and is formatted as Mac OS Extended. It’s also important that your Mac meets the minimum requirements for the OS you’re installing. Apple’s website offers the exact system requirements for each version.
How to Use the Createinstallmedia Terminal Command
From OS X Mavericks forward, in the installer packages is a hidden command that you can enter into Terminal to create a bootable copy of the installer. This Terminal command, called createinstallmedia, creates a bootable copy of the installer using any drive connected to your Mac. This example uses a USB flash drive. Here’s how to do it: For macOS Catalina: For macOS Mojave: For macOS High Sierra: For OS X El Capitan For OS X Yosemite: For OS X Mavericks:
