Booting a Mac with a boot disk is pretty straight forward in most cases ***:
- Connect the macOS Big Sur beta install drive to the Mac
- Restart the Mac if it’s already started up, otherwise boot it up as usual
- Immediately hold down the OPTION key upon Mac boot, continuing to hold OPTION / ALT until you see the Mac boot menu
- Select the macOS Big Sur installer volume to start the Mac from
What if the Mac won’t boot from the macOS Big Sur USB bootable install drive?
*** Note that on some newer Macs with the security chip you may need to manually enable the ability to start the Mac from an external boot disk. Do this by:
- Reboot the Mac holding down Command + R to go into Recovery Mode
- Select “Startup Security Utility” from the Utilities menu and authenticate with admin
- Choose to “Allow booting from external media”
This will allow the Mac to boot from the Big Sur boot install disk as usual with the directions above.
Regardless, once the Mac is booted from the macOS Big Sur beta installer drive, you can format the Mac, partition it, modify and create APFS volumes, restore from Time Machine, clean install, upgrade Macs to MacOS Big Sur, and much more.
Did you make a macOS Big Sur beta bootable installer drive successfully with the command line approach detailed here? Did you use another method to create a Big Sur boot disk? Share your thoughts and experiences in the comments below.
