Mac OS - Startup Keyboard Commands
This document lists helpful keyboard commands that can be used at startup.
Startup Keystrokes
Below are keyboard command keys/key combinations and their respective results:
- C: forces the Macintosh to boot from a CD, DVD, or USB thumb drive if it is present
- T: starts the computer in Target Disk Mode, after which one can then access the internal hard drive by connecting the computer to another via Firewire, Thunderbolt, etc
- Shift + up arrow: starts in Safe Mode
- Spacebar: opens the Extension Manager (Mac OS 9 only)
- Command: turns off virtual memory (Mac OS 9 only)
- Command + R: boots from the recovery partition, if present (Mac OS 10.7 and up)
- Command + S: starts the computer in Single User Mode, wherein the user can interact with a command terminal
- Command + Option: rebuilds the desktop (Mac OS 9 only)
- Command + Option + P + R: clears PRAM
- Option + Command + Shift + Delete: bypasses the current startup volume that Macintosh will try to boot from the next available device that has a valid system folder
- Hold Mouse button down: ejects removable media
- Option: allows you to select a boot volume on open firmware machines