Wednesday, April 3, 2024

Checking Bootable Systems Using bputil

Howard Oakley:

Apple gives the user control over the level of security to be used, in Startup Security Utility, in Recovery. For this to work with boot volume groups (BVGs), each must have its own set of boot security policies, determined by its LocalPolicy.

Without a valid LocalPolicy, Apple silicon Macs will refuse to boot from what would otherwise be a bootable BVG. This article extends my previous account of what makes a disk bootable by explaining more about LocalPolicy, and how you can use the command tool bputil to check it.


LocalPolicy is created when installing macOS to an external disk, when the boot volume group on that disk is assigned its Owner. It can also be created when selecting the boot volume group on a bootable external disk to be the startup disk, if it doesn’t already have a valid LocalPolicy, for example when you want to boot from an external disk previously created using another Mac. This is commonly the point at which failure occurs.


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