Startup keyboard shortcuts Press the key or key combination until the expected function occurs/appears (for example, hold Option during startup until Startup Manager appears, or Shift until "Safe Boot" appears). Tip: If a startup function doesn't work and you use a third-party keyboard, connect an Apple keyboard and try again. Key or key combination What it does Option Display all bootable volumes (Startup Manager) Shift Perform Safe Boot (start up in Safe Mode) C Start from a bootable disc T Start in FireWire target disk mode N Start from NetBoot server X Force Mac OS X startup (if non-Mac OS.