The macOS High Sierra update has netted a few weird upgrades where I had to start over, restore, or boot into safe mode (e.g. if you DEP a device that forces encryption in Sierra and then gets into a loop after a High Sierra update is started). So I’ve been using modifier keys more than usual. The following startup modifier keys are available in macOS High Sierra:
- Alt or Option key: Access Mac Startup Manager, which allows you to select a wireless network and then choose which volume you want to boot to.
- C: Mostly legacy, boots to volumes on a CD, DVD, or USB drive.
- Command-Option-P-R: Resets the parameter RAM (or PRAM for short).
- Command-Option-R: Same as Recovery Mode, but over the Internet.
- Command-R: Boots into the macOS Recovery Mode, useful when doing an internet restore or using Disk Utility to repair a volume.
- Command-S: Enables Single User Mode.
- Command-V: Boots into Verbose Mode, so you see a log of everything during the startup process.
- D: Diagnostics mode starts up using Apple Hardware Test or Apple Diagnostics utility, for checking the hardware of your system.
- Option-D: Load Diagnostics tools over the Internet.
- Eject key, F12, or mouse/trackpad button: Ejects any removable media inserted.
- N: NetBoot attempts to boot to a NetBoot volume on a network.
- Option-N: NetBoot automatically to the default boot image
- Shift: Safe Boot verifies the startup disk and repairs directory issues, disables user fonts and clears the cache for them, only loads required kernel extensions and clears the cache for them, clears system caches, and disables startup and login items.
- T: Target Disk Mode, which sets the system as a disk that can then be mounted on another system (if FileVault encrypted, you may need to enter a password to mount the volumes on the disk).
- X: Boot to a macOS startup disk when otherwise booting to a Windows partition or startup manager.
