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MacOS Recovery

· 2 min read
Chuan-Heng Hsiao
Research Developer @ Boston Children's Hospital

Recently a colleague accidentally changed their Mac system settings through /etc/synthetic.conf. This caused the collegue could not even login into the Mac with any account.

We then found the following mac recovery steps from the Apple Website:

In case this page may disappear in the future:

  • With Apple Silicon:
    • Turn on your Mac and continue to press and hold the power button as your Mac starts up.
    • Release the power button when you see the startup options screen, which shows your startup disks and a gear icon labeled Options.
    • From this window you can start up from a different disk, start up in safe mode, use macOS Recovery, and more.
  • With Intel-based Mac:
    • Command (⌘)-R: Start up from the built-in macOS Recovery system.
    • Option (⌥) or Alt: Start up to Startup Manager, which allows you to choose other available startup disks or volumes.
    • Option (⌥)-Command (⌘)-P-R: Reset NVRAM or PRAM.
    • Shift (⇧): Start up in safe mode.
    • T: Start up in target disk mode.

The Mac is a 2014 Intel-based Mac. We use Command (⌘)-R to get into the built-in macOS Recovery system. In addition, we connected an external-drive to the Mac. We were able to:

  • Select this external-drive as the target disk.
  • Install MacOS on this external-drive.
  • Reboot the Mac through this external-drive.
  • Found the /etc/synthetic.conf in the internal disk and rm /etc/synthetic.conf.