Open the “Terminal” application, it’s found in the Utilities folder and you can also launch it from hitting Command+Spacebar typing Terminal and hitting return.Connect the USB flash drive to the Mac if you haven’t done so already, name the drive “UNTITLED”.Mistakes with syntax can lead to permanent data loss, or the erasure and formatting of the wrong disk, so proceed at your own risk. This process requires using the command line, if you are not comfortable using the Terminal than it is better to avoid this process.
How to Make a Bootable macOS Catalina 10.15 Beta USB Installer Drive The Mac will also need to be online so that it can download the MacOS Catalina installer, if that hasn’t already be accomplished. Knowledge and understanding of the command line and Terminal.
Bootable USB installers offer an easy way to upgrade multiple Macs to macOS Catalina, to perform clean installs of MacOS Catalina, to perform maintenance from a boot disk like formatting disks, modifying disk partitions, and performing restorations, and much more.