Back in the day of Mac OS 7.x-9.x, if you had a problem, one of the first thing you would think of is extensions conflicts. To test this theory, you would boot up holding the shift key to disable extensions. Well, Apple has added the same thing to Mac OS X. If you hold down the shift key at startup, you will do a Safe Boot into Safe Mode. In this mode, you startup disk is automatically checked for errors, only the required kernel extensions are loaded, and only Apple-installed startup items are loaded. This way, you can see if that newly installed software is conflicting with some system level software.

Using either the latest version of TechTool Pro or DiskWarrior, you can check and repair your hard drive's decretory files. These files contain all the information your hard drive needs to find files. If the directory becomes corrupted, the hard drive may not be able to find files, or may look in the wrong place for a file. This will cause extreme problems, that could lead to data loss.

Mac OS X does have some quirks sometimes such as graphical artifacts, things not showing up, or changes not being applied. If you have made sure you did everything right, log out and log back in via the Apple menu. This is nearly identical to restarting, except it is MUCH faster. Then, retry what you were having problems with, to see if it works now.

Remember how force quitting applications in the classic Mac OS would usually not work, and 9 times out of 10 bring the entire system down? That has all changed with OS X. Because of Unix's protected memory, using command+option+escape now brings up a window, with a list of applications to force quit (including the finder). Once you do a force quit, you are free to work on anything you wish, including launching that application again, and starting over with it. No longer is Force Quitting a lesson in futility.

Because of Mac OS X's Unix structure, it's not uncommon to run into problems with permissions. These problems can be very odd in nature, and hard to actually troubleshoot. By using the Disk Utility in your utilities folder, you can repair the permissions of your startup disk.

Mac OS X has some built in maintenance tasks that are scheduled to run very late at night (on a daily, weekly, and monthly basis). If you shut down or sleep your computer at night, these tasks will not get run. To run them at your leisure, you can use a utility such as OnyX.

Mac OS X makes extensive use of cache files to hold all different sorts of information. Sometimes, these caches can become corrupt, making their associated programs unstable. To easily clean out your computer's caches, use a utility such as Panther Cache Cleaner. This is especially true for the Mac Help application.

Just like in the Mac OS of old, preference files can become corrupt. This can cause a program to stop running correctly, or just acting strange. One of the first things you should do if this happens is delete the preference file(s) associated with that program. To assist in finding corrupt preferences, use the program Preferential Treatment.

Archive and Installation is basically a clean installation of the classic Mac OS days. When you install Mac OS X using this method, your settings and data from old installations are saved, and you get a band new OS to run. If you get to the point where a reinstallation is necessary, try this option first. If you need instructions on how to do this, see this Knowledge Base document.

If you are having problems printing, adding printers, or any other situation that involves printing, then the program to try is Print Setup Repair. With it, you can fix a variety of problems related to printing.

Various system settings are stored in this RAM, and they can become corrupted from time to time. If you are experiencing strange problems, try resetting the PRAM by holding down the command+option+P+R keys while starting up. Keep holding down the keys until your hear the startup chime two times. Let go of the keys, and the computer will continue to start up.

Another type of RAM that stores obscure settings (most notably firmware), is the NVRAM. Again, if this becomes corrupted, very odd problems could crop up with your Mac. To reset the NVRAM, holding down the command+option+O+F keys while starting up. This will start you up into Open Firmware, where you can enter commands into the prompt. Enter the following commands to reset the NVRAM and restart your Mac:

1. reset-nvram (hit return)
2. reset-all (hit return)

The Power Management Unit controls various I/O aspects of Apple laptops. If the PMU is corrupt, a wide variety of problems can occur. To reset the PMU, follow the directions on the Apple Knowledge Base.

Similar to the PMU for laptops, desktops Macs have a microcontroller that handles many I/O functions (With G5s it is called the PMU). Again, if this becomes corrupt, strange happenings can occur. To reset the CUDA/PMU switch, you will have to open your Mac, and look around on the motherboard for a white button (many times it is near the RAM slots). Press this button once (only once) to reset the CUDA/PMU. NOTE: Late 2004 and later G5's no longer have a PMU, but rather have a SMU. To reset that, shut down the computer, pull the plug from the wall outlet, wait 15 seconds, plug it back in, and restart.

If you have used Fontbook to disable various fonts that you think are of no use to you, and now your iApps won't launch. This is probably due to making certain fonts inactive. If the Helvetica and Lucida Grande fonts are grayed out, activate them to regain control of your iApps.

AppleJack is a command line utility to be run in Single User mode. It allows you to repair permissions, fix disk errors, check preference files, and clear cache files all without launching a GUI (Graphical User Interface).

If your /tmp file is suddenly missing, various action such as starting Classic, printing, software update, file sharing, and burnings discs will not function. To fix this, open Disk Utility, and repair permissions on your hard drive. Those services should now be restored.

While this won't help after the fact, this is possibly the most important prevention you can do. You should always backup your important data to CD, DVD, external hard dive, iDisk, or anything else which is not your main hard drive. If you have a proper backup, and run into a situation in which data loss occurs, you will be extremely happy you have a backup of those unique files.

• Shift=Safe Mode
• Command + S=Single User Mode
• Command + V=Verbose Mode (watch the Start-up status)
• Option=Volume List (A.K.A Startup Disk)
• Command + Option + P + R=Reset PRAM
• Command + Option + O + F=Start into Open Firmware

• MacFixIt
• Micromat
• Alsoft
• OnyX
• Panther Cache Cleaner Print Setup Repair
• Apple Support Discussions
• PMU Reset Info
• AppleJack
• Preferential Treatment