

Oddly, on Intel Macs running Big Sur, the Data volume isn’t shown as a separate volume, but on M1 Macs it is.

Clicking on the Eject tool for the System disk brings a helpful dialog which offers to unmount both System and Data volumes.

Once booted from the internal disk again, ejecting the bootable external disk isn’t fault-free. Your M1 Mac will then restart from the selected disk. In the first screen displayed there, rather than select the Options item to proceed to Recovery, select the disk which you want to boot from and click Continue underneath it. Its new equivalent is in the opening of Recovery Mode. M1 Macs lack the old Startup Manager, and holding the Option key during startup does nothing at all. When you want to restart from the internal disk, the Startup Disk pane is your best option. You’ll have to go through the whole process of setting your AppleID to work, negotiating two-factor authentication for this ‘new Mac’, and so on, until you can finally use your external disk fully. With AppleID and current setups, what you now effectively have is not simply another boot disk, but a whole new Mac bar the hardware. This should be relatively rapid, and at the end your Mac will automatically restart into the freshly installed copy of Big Sur on your external disk. Then select the external disk and click Continue.įollow the installation process through to completion. When it invites you to select the disk on which you want to install Big Sur, if you don’t see your external disk, click on the button to show all available disks. Then open the Install macOS Big Sur app, and proceed.
