Should a problem occur with macOS during a restart, perhaps because a storage space on the SSD is defective and thus a system component is no longer intact, this will be recognised by the startup process since the seal will now be invalid. So macOS itself cannot be changed by any software that you install as a user. And snapshots cannot be changed, even by the system itself. For further security, these Macs also do not start directly from the system volume, but from a snapshot of the system.

This seal is stored either in the T2 chip of the newer Intel Macs or in the Secure Enclave of the Apple M1/M2.Įach component of the system is signed in hierarchical order, and any change to a component would also invalidate the seal that represents the top level. Since macOS Big Sur, macOS has its home on its own volume, which is both read-only and cryptographically signed and sealed (referred to as a Sealed System Volume). In the past it was helpful to reinstall the system if you wanted to correct some Mac problems, but today this solution doesn’t make as much sense.

Start with Why for mac instal