Web Excursions 2021-11-10

Using an M1 Mac: Some Basic Principles by eclecticlight.co

  • Although M1 Macs have some unique restrictions, in many ways they’re among the most flexible of Apple’s recent models.

  • There are four scenarios to prepare for in terms of disaster recovery.

  1. Loss or damage to data on the Data volume, on the internal SSD.

    • The response is to open Time Machine and restore the files from there

  2. Damage to the System.

    • This is prevented by the fact that M1 Macs, like Intel models, booting from Big Sur or Monterey

      • do so not from a mounted volume,

      • but from a signed and sealed snapshot.

    • Because snapshots are read-only and can’t be changed in any way, the chances of a corrupt System snapshot occurring are very low.

    • in most cases you should expect to migrate your data back from a Time Machine backup or a copy or clone of the Data volume, on an external disk.

  3. Soft damage to the whole of the internal SSD.

    • What the user can’t normally see is that this isn’t just the container (partition) for macOS, but includes two hidden containers too:

      1. the Pre-Boot container is used for what is effectively the firmware

      2. The other container holds a Recovery system, although in Monterey that copy isn’t the one normally used for Recovery

    • If the Pre-Boot container is damaged, the Mac is unable to boot, even though it may be connected to a bootable external disk,

      • as the only Pre-Boot it can use in the early part of the boot process is that located on the internal SSD.

      • In that case, the only way forward is to put the Mac into DFU mode

      • M1 Macs are, to the best of my knowledge, the only Macs that Apple has made which can be taken right back and restored by the user in this way.

      • It normally takes less than 15 minutes.

  4. Hard failure of the internal SSD

    • Because it’s soldered to the logic board, the only remedy is a replacement logic board,

      • which is performed under warranty and AppleCare by an authorised service provider.

    • Contrary to some opinion, M1 Macs are straightforward to boot from an external SSD,

      • although you must never confuse that process with booting an Intel Mac from an external disk.

      • In the latter, the whole of the boot process can run from the external SSD.

      • M1 Macs invariably start their boot process from their internal SSD, and only then transfer to the external boot system.

    • Once you’ve made a bootable external disk, and its ownership is recognised by macOS so that Mac can start up from it, you can use that disk with other M1 Macs.

    • Unlike Intel Macs with T2 chips, you don’t have to change an M1 Mac’s security settings for it to boot happily from an external disk.

    • You can also repartition your M1 Mac’s internal SSD to provide additional containers, and install multiple bootable copies of macOS on that internal storage.

    • You can also install multiple versions of macOS in a single container if you wish.