How to Shut Down a Mac with OS X Yosemite
Turning off the power without shutting down your Mac properly is one of the worst things you can do to your poor Mac. Shutting down your Mac improperly can really screw up your hard or solid-state drive, scramble the contents of your most important files, or both.
If a thunderstorm is rumbling nearby, or you’re unfortunate enough to have rolling blackouts where you live, you may really want to shut down your Mac.
To turn off your Mac, always use the Shut Down command from the Apple menu or shut down in one of these kind-and-gentle ways:
Press the Power button for approximately two seconds and then click the Shut Down button in the Are You Sure You Want to Shut Down Your Computer Now? dialog.
On keyboards that don’t have a Power key, press Control+Eject instead, and then click the Shut Down button that appears in the Are You Sure You Want to Shut Down Your Computer Now? dialog.
You can use a handy keyboard shortcut when the Shut Down button (or any button, for that matter) is highlighted in blue and pulsating slightly. Pressing the Return key is the same as clicking that button.
The Are You Sure You Want to Shut Down Your Computer Now? dialog sports a check box option in OS X Yosemite: Reopen Windows When Logging Back In. If you select this check box, your Mac will start back up with the same windows (and applications) that were open when you shut down or restarted.
Most Mac users have been forced to shut down improperly more than once without anything horrible happening, of course — but don’t be lulled into a false sense of security. Break the rules one time too many (or under the wrong circumstances), and your most important files will be toast.
The only time you should turn off your Mac without shutting down properly is when your screen is completely frozen or when your system crashed due to a kernel panic and you’ve already tried everything else. A really stubborn crash doesn’t happen often — and less often under OS X than ever before — but when it does, forcing your Mac to turn off and then back on might be the only solution.