Since November 2012, I’ve been a proud owner of a MacBook Air (13-inch, Mid 2012), and it is with sadness that I must accept it has reached its end-of-life with the upcoming release of Big Sur.

It came with Mountain Lion (OS X 10.8), and with each upgrade, I always perform a clean install because I prefer starting without clutter.

There are many guides on how to create a bootable installer, but for doing this I’ll follow the instructions from Apple on how to create a bootable installer for macOS, along with how to erase a disk for Mac, since I will do a clean installation.

I will use a 16 GB USB drive labeled “INSTALLER” for creating my bootable drive.

And these are the instructions:

  1. Download macOS Catalina from the Mac App Store
  2. Once downloaded run the following command:
     sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/INSTALLER
    
  3. Restart your Mac and press the alt-option key as soon as it restarts, so you are prompted to select a Startup Disk
  4. Select the macOS Catalina Installer
  5. Select Disk Utility and click Continue
  6. Choose View > Show All Devices from the menu bar, and select APPLE SSD
  7. Click Erase and assign these settings:
    1. Name: APPLE SSD
    2. Format: APFS
    3. Scheme: GUID Partition Map
  8. Click Erase
  9. When done, quit Disk Utility
  10. Select Install macOS from macOS Utilities, and click Continue
  11. To set up the installation of macOS Catalina, click Continue
  12. Agree to the terms of the software license agreement
  13. Click Agree on the next prompt
  14. Select APPLE SSD and click Install
  15. Sit back and relax

Once the installation is done, you’ll be asked to configure your Mac.

And that’s it! You’ll have a “brand new” Mac!