What is a kernel panic? (Mac OS X)
Summary
UNIX-style operating systems (such as Mac OS X, Mac OS X Server, AIX, and A/UX) may experience a type of error called a "kernel panic," which may provide information useful for software developers.
A kernel panic is a type of 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 follow when the operating system is not able to recover from a different type of error. A kernel panic can be caused by damaged or incompatible software or, more rarely, damaged or incompatible hardware.
Products Affected
Mac OS X 10.0, Mac OS X 10.1, Mac OS X 10.2, Mac OS X 10.3, Mac OS X 10.4, Mac OS X 10.5
Appearance of a kernel panic
The appearance of a kernel panic varies, depending on which version of Mac OS X you are using.
Mac OS X 10.2, 10.3 or later
A kernel panic in Mac OS X 10.3 or later
Mac OS X 10.2 introduces automatic kernel panic logging, so you may not see any visual indication of a kernel panic. You can check the kernel panic log any time that you must force restart your computer, using either the power button, interrupt button, or the Control-Command-power key combination. The kernel panic text is added to the log the next time you restart the computer, assuming that you have not reset PRAM at the same time (the kernel panic text is stored in PRAM until you restart). The file is named "panic.log", and it is located on your startup disk at:
/Library/Logs/
If you do see visual indication of a kernel panic, it will appear as a message that says "You need to restart your computer. Hold down the Power button for several seconds or press the Restart button.".
A kernel panic in Mac OS X 10.2 through 10.2.8
Mac OS X 10.0 to 10.1.5
When this happens in either Mac OS X or Mac OS X Server version 10.0 to 10.1.5, white text on a black background is drawn on top of the last video image on the monitor before the error occurred. The text of a panic might contain something like this:
- "Unresolved kernel trap(cpu 0): 0x300 Data access DSISR=0x40000000 DAR=0x0000006c PC=0x06d77510 MSR=0x00009030
generating stack backtrace prior to panic:
backtrace: 0x06d77510 0x0002a1fa 0009d1ef 00099440 012f4102 kernel modules in backtrace: com.apple.filesystems.cddafs(1.0) @ 06d75000
Memory Access Exception(1,0,0) Waiting for remote debugger connection"
Example kernel panic in Mac OS X 10.0 to 10.1.5
What's in a kernel panic message?
Kernel panics generate information that may aid developers in the investigation of a software issue. It is useful to record any information that appears during a kernel panic, in addition to how the computer was being used when the kernel panic happened--was the computer starting up, shutting down, or performing a particular task?
Tip: Update to the latest version of Mac OS X to avoid certain potential kernel panic situations.
Recording kernel panic information
For Mac OS X 10.2, 10.3 or later, the kernel panic text is logged automatically for you as described above. If you want to send the information to Apple for potential investigation of the issue, see "Mac OS X, Mac OS X Server: How to Log a Kernel Panic".
For Mac OS X 10.0 to 10.1.5, the computer is in a non-responsive state during a kernel panic, so you can't take a screen shot. But you can type the information on another computer or write it out by hand. Also see "Mac OS X, Mac OS X Server: How to Log a Kernel Panic".
Troubleshooting
If you have a recurring panic issue and don't know how to troubleshoot it, see "Isolating issues in Mac OS X".