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boot macOS from USB

macOS from scratch

This guide will help you to perform a clean install of macOS from the USB interface of your MAC.

You'll need:

  • a USB-Stick or an SD-Card (min. 14GB)
  • a downloaded installer for macOS

Prepare SDcard

Open your Terminal and copy this into the command line interface:

diskutil list

This command will list all the connected drives. In my case /dev/disk3 is the SDcard to which I'd like to copy the macOS Installer.

Let's reformat and rename the SDcard. Replace /dev/disk3 with the number of your USB-Stick:

diskutil eraseDisk HFS+ macOS_installer /dev/disk3

If the command went smoothly the output will be similar to mine:

Initialized /dev/rdisk3s2 as a 15 GB case-insensitive HFS Plus volume Mounting disk
Finished erase on disk3

Copy macOS installer to SDcard

You have:

  • downloaded the macOS installer APP to your Applications folder (default)
  • renamed your USB drive to macOS_installer
  • backed up all your data

Copy following command to your Terminal. In my case it will create a macOS Monterrey installer:

sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS_installer

Depending on the current language settings of your MAC, your downloaded macOS installer might be listed under a different name in your Applications folder. DON'T change the name of the APP. The command above will work anyway.

Terminal will ask you for confirmation. Type Y and treat yourself to a cup of tea ;) ...

A few minutes later your bootable USB-install media is ready for use.

By rebooting your MAC and holding down the ⌥ option key (Power Button for newer MACs with Apple silicon), you'll be able to choose the freshly made Installer as a boot-device.

That's it! - follow the instructions on screen.

On my next guide, I'll explain how to customize and setup your OS in a breeze with a script.

Hope to see you around on my site!

-- Pascal