Kernel Panics

A kernel panic is a system error that occurs when the core (kernel) of an operating system receives an instruction in an unexpected format, or that it fails to handle properly. A kernel panic may also occur when the operating system is not able to recover from a different type of error, or it can be caused by damaged or incompatible software. More rarely, damaged or incompatible hardware can cause one as well.

MacOS X 10.0-10.1.5 Kernel Panics

When a panic is displayed with this early version of OS X, you will see some text overwriting the last rendered screen before the kernel panic came into effect. This text will show you the state of the System at the time of the crash, and may also display some kind of a description of what went wrong, so have a look at it before you reboot, just incase it might be hardware related. See this picture for an example.

MacOS X 10.2 onwards, Kernel Panics

Mac OS X 10.2 introduces automatic kernel panic logging, so you may not see any visual indication of a kernel panic. The kernel panic text is added to the log the next time you restart the computer. Do not reset PRAM, as the kernel panic text is stored in PRAM until you restart the Mac. This file is called "panic.log", and it is located on your startup disk at <hard disk name>/Library/Logs/. See this picture for an example.

On an additional note, when you want someone to fix your Mac for you, it is always a good idea to do a printout of the last kernel panic that happened, from this log, so that they can extract clues from it. Also, kernel panics are normally very infrequent. So when you start to get regular kernel panics then there is something definitely wrong with your setup. Remember, kernel panics replace OS 9’s System Errors, so if a panic occurs, it is related to the last thing that was performed on your computer.