M1 Mac cannot boot from external drive with FileVault enabled

Originator:jk
Number:rdar://FB9037296 Date Originated:3/9/2021
Status:Open Resolved:
Product:MacBook Air Product Version:M1, 2020
Classification: Reproducible:Yes
 
Summary: When macOS 11.2.2 is installed on an external Thunderbolt 3 SSD, the Mac can boot from it properly, but only if FileVault is disabled. Once FileVault is enabled on the external drive, the Mac cannot boot and gets into a restart loop.

Steps to reproduce:
- Attach a Thunderbolt 3 SSD.
- Using Disk Utility, erase the external SSD as APFS/GUID Partition Map.
- Download Big Sur 11.2.2 installer and run it, with the external SSD as the destination.
- Install a fresh copy of macOS on the external SSD, all defaults, no migration.
- At this point, the Mac can restart from the external SSD, and all is well.
- Now, while booted from the external SSD, enable FileVault. Wait until encryption finishes.
- Restart.
- The Apple logo appears and the progress bar begins to fill, but then the Mac restarts in recovery mode. If I then select the external SSD as the startup volume, the cycle repeats. At no point does the login window appear, nor am I prompted to unlock the external FileVault volume.

Expected behavior:
- When an external SSD with a properly installed copy of macOS is installed, with FileVault enabled, and that volume is selected as the startup volume, the Mac should in fact complete the startup process.

Comments


Please note: Reports posted here will not necessarily be seen by Apple. All problems should be submitted at bugreport.apple.com before they are posted here. Please only post information for Radars that you have filed yourself, and please do not include Apple confidential information in your posts. Thank you!