Macintosh Safe Boot

Starting with Mac OS 10.2 it is possible to start a Macintosh in Safe mode. Hold down the Shift key during startup to force the computer to start in safe mode. Starting in safe mode does the following things:

• It forces a directory check of the startup volume.
• It loads only required kernel extensions (some of the items in /System/Library/Extensions).
• It runs only Apple-installed startup items (some of the items in /Library/StartupItems and /System/Library/StartupItems - and different than login items).
• Mac OS X 10.4.x and later: It disables all fonts other than those in /System/Library/Fonts .
• Mac OS X 10.4.x and later: It moves to the Trash all font caches normally stored in /Library/Caches/com.apple.ATS/(uid)/ , where (uid) is a user ID number such as 501.
• Mac OS X 10.4.x and later: It disables any Login Items.

Safe Mode can be useful for troubleshooting. However, certain Mac OS X features do not work when you are started up in Safe Mode. For example, you can't use DVD Player, capture video in iMovie, use an AirPort card, use some audio input or output devices, or use an internal or external USB modem.

NOTE: There have been some reports of kernel panics occuring during startup which seem to be related to bad font cache files. Doing a safe boot and then restarting the computer will move the bad font cache files into the trash and possibly fix the problem.