Have an M1 Mac? You can create an external, bootable drive for it — but the disk won’t work with Intel Macs.
There are benefits to having an external, bootable drive. For example, it allows you to continue working on a different computer or helps you fix a Mac that’s having problems.
To create an external, bootable M1 Mac drive, you’ll need (in addition to an M1 Mac, naturally) a Thunderbolt 3 SSD and a copy of the macOS Big Sur 11.2 (or later) installer app (you could perhaps try 11.0-11.1, but most reports say this isn’t reliable).
OWC offers several great Thunderbolt SSDs. Two I recommend are:
Note: you could use a drive other than a Thunderbolt 3 SSD, but I’d recommend this option as it’s fast and reliable.
You can obtain the installer app from the App Store:
Creating the drive
Now follow these steps:
- Connect your external drive.
- Use Disk Utility to erase the drive completely, then format it in APFS without encryption. (Disk Utility is located in the Utilities folder in the Applications folder).
- Launch the Install macOS Big Sur app.
- You’ll be asked to choose the drive/disk on which to install macOS Big Sur.
- Select your external disk. If it’s not showing up, click on the button to show all available disks. Then select your formatted drive, and click Continue.
- Follow the installation process.
When your Mac restarts, it will boot from the newly created external drive to complete the installation.
After the external drive is created
To get back to your internal drive as the startup volume, open the Startup Disk preference pane while macOS is running on the external drive and select the internal drive. Then click Restart.
You’ll have to unmount the external drive after the restart is complete.