X-quest: Safe mode, booting without extensions


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The more things change, the more they stay the same. Evidence of this comes to us in the form of a pair Apple Knowledge Base articles that explain the how's and why's of booting into "Safe Mode," which is described as: "[T]he state Mac OS X is in after a Safe Boot. A Safe Boot is a special way to start Mac OS X when troubleshooting."

According to the article, starting up into Safe Mode does three things to simplify the startup and operation of your computer:
* It forces a directory check of the startup (boot) volume;
* It loads only required kernel extensions (some of the items in /System/Library/Extensions); and
* It runs only Apple-installed startup items (some of the items in /Library/Startup Items and /System/Library/Startup items - and different than login items).

Taken together, these changes can temporarily resolve issues caused by startup volume software or directory damage.

If this description gives you a feeling of deja vu, you're not alone. Moreover, getting your Mac into Safe Mode should be equally familiar: hold down the "Shift" key during boot up.

A second Knowledge Base article describes the particulars of booting into Safe Mode under X. Specifically, users shouldn't press the Shift key until after the start up chime sounds.

Instead of OS 9's "Extensions Off" message, X will indicate it is starting in Safe Mode by displaying a gray apple and a spinning gear instead of the usual progress bar. When these appear the user should release the Shift key.

As with Classic, leaving Safe Mode requires a reboot.

Now that we know how to do it, the only thing we need to know just why we'd need to start in Safe Mode in the first place -- only one of my three Macs has ever crashed running X and that involved several "adult" CDs of dubious (Vietnamese) provenance ;>...