Last Week on My Mac: 1 True Recovery

Before the Recovery partition was introduced in Mac OS X Lion, in 2011, Mac users had managed to survive all manner of problems and disasters without its aid. Over the next nine years, Recovery became steadily more complex, in 10.12.4 gaining a second remote recovery mode.

By 2016, there were 14 different startup modes and variations, each engaged using a different combination of keys. In my latest guide to startup modes, it takes over a thousand words to explain just their basics, with links to several other articles explaining more. For anyone new to the Mac, even for old-timers, that’s a lot of knowledge required before you can say you’re proficient using your Mac.

In 1 True Recovery (1TR), Apple has gone back to the drawing board and designed a complete suite of recovery tools from scratch. Entered using a single action – holding the Power button until the Mac starts loading 1TR – it has a graphic interface throughout, and provides detailed online help. As I have explained, it integrates all recovery tools under a single roof, except for the ultimate manoeuvre of engaging DFU mode and connecting to Apple Configurator.

Architecturally, Apple has taken a major step forward in separating 1TR from all installed versions of macOS. In the days of HFS+ boot disks, Recovery Mode was run from a separate partition, as an HFS+ volume is. When Apple migrated the system to APFS, Recovery ended up on its own APFS volume, sharing space with the system volume. Although it’s still possible to install multiple versions of macOS within a single APFS container (the equivalent of an HFS+ partition), that results in multiple Recovery volumes. Start up in the wrong one and run First Aid in Disk Utility, and you can end up repairing more recent APFS file systems with older tools.

Many of the startup modes of Intel Macs are run from UEFI apps which are themselves stored in firmware, so can only be updated as part of a firmware update. Two – local Recovery and Diagnostics – launch minimal runtime environments from disk images from the Mac’s internal storage. Their only fallbacks, Internet Recovery and Internet Diagnostics, download signed disk images which are then mounted and run to provide the service.

On the internal SSD of an M1 Mac, 1TR now has its own partition (APFS container), which separates it completely from the six volumes which make up the Big Sur boot container. Together with the iBoot System Container (iSC), which is required for the boot process, it forms what is in effect an extension to the M1 firmware. Because this is stored on the SSD, it is readily updated as part of a normal macOS update, without any of the trouble that EFI firmware has suffered. Neither does it require the protracted chipset juggling which has to take place when updating T2 firmware.

In this new scheme, there’s just one True Recovery system on each M1 Mac, regardless of how many different versions of macOS you might have installed. It also works for other operating systems: if you have Linux alongside, or on an external disk, there’s always 1TR there with its per-system controls over security policy, and disk maintenance tools. Individual systems can provide their own local recovery support too, but 1TR is there when you most need it.

There are other benefits to storing iSC and 1TR on the internal SSD. EFI and T2 firmware updates haven’t been free of their own problems. Innumerable users have complained that firmware updates have brought new problems such as kernel panics when trying to wake from sleep, or exacerbated an existing one. Rolling back to the previous version of macOS seldom offers any relief, as Intel Mac firmware can’t be downgraded.

Armed with a second Mac and a copy of Apple Configurator 2, those with M1 Macs can now roll their entire system back to any previous release of macOS (compatible with Apple Silicon models) in less than 15 minutes by restoring the appropriate IPSW image. If a new version of Big Sur makes your M1 Mac unstable, or incompatible with existing software, you can now restore its entire system to the previous, stable release.

One True Recovery may now seem fine detail, and restoring with Configurator may seem irksome. As we get used to it, and realise the problems which it solves, it will prove itself as a major advance for Macs and their users.