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On a sheet of Mac keyboard shortcuts for booting, one of them says, "hold down shift while booting and the computer will not load login items or extensions".

Am I wrong, or are Mac OS "extensions" something that were phased out a long time ago? (In other words, with OS X Lion, the shift key simply cancels loading the login items, period?)

Note that, of course, I know that "extensions" has meaning in other apps -- Firefox, Safari, Thunderbird, etc. But please confirm my Mac OS X suspicion as I describe it above.

(Yep, I know this is related to my other question. Getting this answer clear will allow me to resolve both questions clearly and designate their correct answers.)

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up vote 6 down vote accepted

Your expectation that extensions are only a thing of the past is incorrect.

Modern Mac OS X uses kernel extensions, which are not identical to the "old school" extensions used in Mac OS 9 and earlier, but yes, there are still such a thing as extensions. You can find them in /System/Library/Extensions.

Apple expands on this in this support document about Safe Mode.

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To expand on the difference between Classic and OS X extensions: most, if not all, of the hardware drivers required by Classic Macs were included in the system software itself, not as separate extensions. In OS X most hardware drivers are provided as extensions. – username Jun 9 '12 at 14:27

To go along with @Daniel's answer: holding down the shift key on startup of OS X should prevent "startup items" from opening.

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You've said the same thing Daniel did. How is yours an "opposite answer"? – CajunLuke Jun 9 '12 at 21:50
Woah! I thought "kernel extensions" and "startup items" were different things! – GEdgar Jun 10 '12 at 0:39
I should say: your answers are complimentary, not identical. He explained extensions then vs. now, while you specified what the keyboard shortcut does. I've edited your answer to make that more apparent. – CajunLuke Jun 10 '12 at 0:45
I read the document Daniel posted and it answered all the remaining questions I have! Sorry. the above apple documnet at the bottom of daniel's answer is great. THANKS -- all done. – estephan500 Jun 15 '12 at 4:24
@estephan500 That's a great question, and it deserves to be asked as its own question, rather than trying to get an answer here in the comments thread. – Daniel Jun 15 '12 at 4:24

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