When you make a backup of a Big Sur startup disk with CCC 5.1.23 or later, CCC will automatically use Apple's proprietary APFS replication utility (ASR) to make an exact copy of the source. This volume is cryptographically sealed, and that seal can only be applied by Apple ordinary copies of the System volume are non-bootable without Apple's seal. Starting in macOS Big Sur, the system now resides on a 'Signed System Volume'. MacOS 11, 'Big Sur' bootability troubleshooting If you're trying to migrate content to a new Mac, use Migration Assistant for that purpose - do not attempt to restore an older Mac's backup onto a new Mac.
No Mac will ever boot from an OS that is older than what it shipped withĪpple has never supported booting a new Mac from an OS that is older than what it shipped with. If you're having trouble with the steps or have run out of options, please let us know how far you got, or how far your Mac gets into the boot process. Before you ask for help, please try the troubleshooting steps below. We're happy to help you troubleshoot your bootability problems.
