The first blow to bless came in macOS 10.11: one of the side-effects of SIP is that it shouldn’t be used to try to set the startup disk. When you do, study its man page very carefully and make sure that you get the command right.
Only if that fails, or if you are trying to perform this task by hand, should you ever need to use the bless command in anger.
If you use a tool such as Carbon Copy Cloner or SuperDuper to clone an existing bootable volume, one of its options should be to make that cloned disk bootable by blessing it. When you install macOS on a volume, the installer should do that for you as part of the service. Making a volume bootable is a task which the user very seldom has to do. If you use any of its other options, there is always the risk that you will render that Mac unbootable (at least temporarily), so you should be extremely cautious. You’ll then be given the inodes and paths to the Blessed System File and Folder on that preboot volume, and the Blessed Volume for the container should be given as the root path, /. Or after mounting the preboot volume, which rather defeats its purpose, perhaps. Try this command on a Mac booted from an APFS volume, and you’ll be disappointed: you either have to run it with privileges as macOS here uses inode numbers instead of paths you can use my free utility Precize to explore inodes and their relatives. The numbers given for each of the lines in the boot settings are the file system inode numbers, which are more persistent than the conventional paths which they resolve to.
Which returns information about the current boot settings, such asįinderinfo: 325985023 => Blessed System Folder is /System/Library/CoreServicesįinderinfo: 342576416 => Blessed System File is /System/Library/CoreServices/boot.efiįinderinfo: 0 => Open-folder linked list emptyįinderinfo: 0 => No alternate OS blessed file/folderįinderinfo: 325985023 => OS X blessed folder is /System/Library/CoreServices Now, the only use of bless which you should be happy with, unless you really know what you’re doing, is configure the Mac to boot not from a local volume but from a server, using NetBoot Īnd more.prepare a volume so that it could be made bootable, by copying boot.efi to the right place.set the two NVRAM variables efi-boot-device and efi-boot-device-data to make any bootable volume the next startup disk.write the information to the volume header which declared that volume as being bootable.This used to be simple, before the advent of SIP, APFS, and Secure Boot in the T2, and came down to a single very complex command bless. The last piece in the puzzle that is the booting of a Mac is understanding how any given volume is made bootable, and how it can be made the next startup volume.
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