Monday, November 27, 2023

A Short History of Recovery in macOS

Howard Oakley:

For the first ten years of Mac OS X, its closest substitute was Single User Mode, or SUM, entered by starting the Mac up with the Command and S keys held down. OS X then booted into the command line, where you could for example repair your startup volume[…]


With Mac OS X Lion, and the delivery of OS X from the App Store, this all changed, when starting a Mac up with the Command and R keys held entered its new Recovery mode, stored in what was termed the Recovery partition. In those days of HFS+, that was just another volume on the boot disk, and could be supplemented with a prepared USB stick containing third-party recovery tools, such as Drive Genius or Disk Warrior.


Prior to macOS Sierra, entering Recovery usually worked with a wireless keyboard; when running Sierra and later, many users found that they had to connect Bluetooth keyboards to a USB port to ensure the startup key combination worked reliably.


Apple silicon Macs, though, had a brand new Recovery system, dubbed 1 True Recovery (1TR), run from a hidden container on their internal SSD, and engaged by pressing and holding the Power button.


From Monterey onwards, starting up in primary Recovery using the Power button boots that Mac into the Recovery volume paired with the current boot volume group. Starting up in fallback Recovery using the doubly-pressed Power Button boots that Mac into the fallback Recovery (frOS) installed in the hidden Apple_APFS_Recovery container on the internal SSD.

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