Some Mac users may wish to create a bootable MacOS Catalina installer drive, typically using a USB flash drive or with another similar small boot disk.
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.
We’ll walk through how to create a boot USB install drive for MacOS Catalina 10.15.
Requirements to Create a Bootable macOS Catalina USB Install Drive
The following prerequisites are necessary to make a bootable installer drive for macOS Catalina:
- USB flash drive (16GB or larger) – this will become the boot install driver for MacOS Catalina, it will be formatted so any data on this drive will be erased to become the boot installer
- A complete “Install macOS Catalina.app” installer application residing in the /Applications/ folder on the Mac (you can download full macOS installers from Terminal with these instructions on newer MacOS releases, otherwise use the MacOS Catalina download link via App Store)
- A Mac compatible with MacOS Catalina
- Knowledge and understanding of the command line and Terminal
The Mac will also need to be online so that it can download the MacOS Catalina installer, if that hasn’t already be accomplished.
How to Make a Bootable macOS Catalina 10.15 Beta USB Installer Drive
This process requires using the command line, if you are not comfortable using the Terminal than it is better to avoid this process. Mistakes with syntax can lead to permanent data loss, or the erasure and formatting of the wrong disk, so proceed at your own risk.
- Connect the USB flash drive to the Mac if you haven’t done so already, name the drive “UNTITLED”
- 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
- Enter the following command at the Terminal command line, assuming “UNTITLED” is the name of the USB flash drive you want to make into the Mac Catalina installer boot disk:
- If the syntax is correct, hit the Enter/Return key and authenticate with the admin password as necessitated by sudo
- Let the creation process build the boot installer disk and complete, it may take a little while
sudo /Applications/Install macOS Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/UNTITLED
After the MacOS Catalina 10.15 USB boot installer drive has been created, it will be mounted on the Mac. At this point it can be used like any other boot disk or installation disk.
The MacOS Catalina boot disk can be used with any MacOS Catalina compatible Mac.
* If you see a “command not found” error message in the terminal, it’s likely because there was a typo or syntax error, or because the “Install macOS Catalina.app” application file was not found in the /Applications/ folder where it is expected to be.
How to Boot with macOS Catalina USB Install Drive
To boot from the MacOS Catalina boot disk, connect it to a Mac, then reboot the computer and hold down the OPTION key to boot into the boot menu, where you will be able to choose the MacOS Catalina installer drive as a boot option.
- Connect the macOS Catalina install drive to the target Mac
- Reboot the Mac as usual
- Hold down the OPTION key upon system boot, and continue holding Option until you see the Mac boot menu
- Choose the macOS Catalina installer volume to boot from
The MacOS Catalina boot disk will allow you to install MacOS Catalina as an upgrade, and also to perform clean installations of macOS Catalina if desired. You can also access the regular bootable installer utilities, including Disk Utility for formatting and partitioning drives, and Time Machine recovery tools for restoring from backups.
Were you successful in making a MacOS Catalina bootable install drive? Did you use another method? Let us know in the comments whatever your experience has been.
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