OS X Startup keyboard commands help in troubleshooting

When troubleshooting, performing maintenance, or otherwise starting up your Mac OSX computer in an abnormal fashion, there are a few keyboard shortcuts that you may or may not know about that can help you. Below is a list of them with an explanation of what they do:

  • X = Force Mac OS X startup
  • Option = Brings up a screen with startup volume choices (slow process, may take a while)
  • Option+Command+Shift+Delete = Bypass primary startup volume and seek a different startup volume (such as a CD or external disk)
  • C = Start up from a CD that has a system folder
  • N = Attempt to start up from a compatible network server (NetBoot)
  • T = Start up in FireWire Target Disk mode (very handy for plugging your Mac into another as an external hard drive)
  • Shift = start up in Safe Boot mode and temporarily disable login items and non-essential kernel extension files (Mac OS X 10.2 and later)
  • Command+V = Start up in Verbose mode.
  • Command+S = Start up in Single-User mode
  • Command+Option+p+r = Zap PRAM. Hold down until second chime.
  • Command+Option+n+v = Clear NV RAM. Similar to reset-all in Open Firmware.
  • Command+Option+o+f = Boot into open firmware
  • Hold mouse button down = Force eject a CD/DVD