"You need to restart your computer" (kernel panic) message appears (Mac OS X v10.5, 10.6)

Products Affected

Mac OS X 10.5, Mac OS X 10.6

Symptoms

In rare situations, your Mac may stop responding and display a message stating "You need to restart your computer". This is called a kernel panic. Here is a sample kernel panic message that may appear:

Resolution

Restart your Mac with a Safe Boot and see if the kernel panic happens again

In most cases, kernel panics are not caused by an issue with your Mac. They are most likely caused by an issue external to your Mac. If the kernel panic doesn't happen again within a few weeks, you don't need to troubleshoot further.

  1. Depending on the model of Mac you have, restart one of these ways:
    • Press and hold the Power button for several seconds to turn off your Mac. Then, press the Power button to startup your Mac.
    • If you have a Restart button, press it.
  2. As soon as your Mac starts up, hold down the Shift key to start up with a Safe Boot into Safe Mode. Note: If you are using a third-party external keyboard and cannot start with a Safe Boot, try using an Apple keyboard instead.
  3. If your Mac has a kernel panic starting up, or while in Safe Mode, jump to the "Troubleshooting a recurring kernel panic" section of this article.
  4. If your Mac starts up without a kernel panic after a Safe Boot, restart your Mac by choosing Apple Menu > Restart…, then let it start up normally. Run Software Update and install all available updates until Software Update reports "Your software is up to date". Mac OS X updates improve the tolerance for external issues such as malformed network packets. For most kernel panics, this is all you have to do.

Important: If your Mac has another kernel panic within a few weeks, continue with this article to diagnose the cause of the intermittent, recurring kernel panic.

Note: It is possible, although very unlikely, that something on your network is sending your Mac malformed network packets which could cause recurring kernel panics. If the hardware and software on your Mac checks out as OK, check the devices on your network. Make sure your router's firmware is up-to-date, and that the router is not malfunctioning.  Refer to your router's manufacturer for service and support.

Diagnosing a recurring kernel panic can be difficult. If you would like to avoid this process, or do not know how to perform any of the following steps, consider bringing your Mac to a Genius at an Apple Store or an Apple Authorized Service Provider for assistance. Be sure to ask that, if the hard disk needs reformatting or replacing, they contact you about escalating your case to a special data recovery service. If you plan to visit an Apple Retail store, make a reservation at the Genius Bar using http://www.apple.com/retail/geniusbar/ (available in some countries only).

Troubleshooting a recurring kernel panic

Tip: To help diagnose recurring kernel panics, record the date and time it occurs, and any information that appears with the kernel panic message.

  • Was the computer starting up, shutting down, or performing a particular task when the recurring kernel panic happened?
  • Is the kernel panic intermittent, or does it happen every time you do a certain thing?
  • Does it occur only when a certain external device is connected, or a device is connected to a certain port?

Note: The following steps require an external disk with at least 10 GB of free space.

Isolate hardware or software as the cause of the kernel panic

  1. Start your Mac from its install media. Note: If a kernel panic occurs while starting up from its install media, go to the "Hardware troubleshooting" section of this article.
  2. Open Disk Utility and use "Repair Disk" on your internal hard disk.

    Important: If Disk Utility is unable to repair the internal hard disk, you should bring your Mac to a Genius at an Apple Store, or an Apple Authorized Service Provider for service and support. Be sure to ask that, if the hard disk needs reformatting or replacing, they contact you about escalating your case to a special data recovery service. If you plan to visit an Apple Retail store, make a reservation at the Genius Bar using http://www.apple.com/retail/geniusbar/ (available in some countries only).
     
  3. Quit Disk Utility.
  4. Install Mac OS X on the external hard disk. Perform a custom installation of Essential System Software only (deselect everything else).
  5. Start up from the external hard disk.
  6. Run Software Update.
  7. Install all updates until Software Update reports "Your software is up to date."
  8. Use the Apple applications on your external hard disk to surf the web, view QuickTime movies, email, print, scan, sync iOS devices, and other things. Continue using your Mac for the amount of time it would usually take for the kernel panic to occur.
  9. If a panic occurs, go to the "Hardware troubleshooting" section of this article to further diagnose the issue.
  10. If a panic does not occur, go to the "Software troubleshooting" section of this article to further diagnose the issue.

Hardware troubleshooting

Check peripheral devices first

Skip this section if you have no peripheral devices.

  1. Power off your Mac.
  2. Disconnect all peripheral devices and Ethernet cables until all you have connected to your Mac is a display, keyboard, and mouse or trackpad.
  3. Power on your Mac and start from the external hard disk.
  4. Use the Apple applications on your external hard disk to surf the web, view QuickTime movies, email, print, scan, sync iOS devices, and other things. Continue using your Mac for the amount of time it would usually take for the kernel panic to occur.
  5. If the kernel panic does not occur: Power down your Mac and connect one peripheral at a time; repeat the above steps until you find the peripheral causing your kernel panic.
  6. If the kernel panic does occur: Proceed to check the internal RAM and third party hardware.

Check internal RAM and third-party hardware

  1. Power off your Mac.
  2. Reseat your Apple RAM, and remove third party RAM and third-party hardware.  If you do not have the Apple RAM that came with your system, reseat the third-party RAM.
  3. Power on your Mac and start from the external hard disk.
  4. Use the Apple applications on your external hard disk to surf the web, view QuickTime movies, email, print, scan, sync iOS devices, and other things. Continue using your Mac for the amount of time it would usually take for the kernel panic to occur.
  5. If the kernel panic does not occur: Your third-party RAM or internal third-party hardware may need to be replaced.
  6. If a kernel panic does occur:  Bring your Mac to a Genius at an Apple Store, or an Apple Authorized Service Provider for service and support. Be sure to ask that, if the hard disk needs reformatting or replacing, they contact you about escalating your case to a special data recovery service. If you plan to visit an Apple Retail store, make a reservation at the Genius Bar using http://www.apple.com/retail/geniusbar/ (available in some countries only).
     

Software troubleshooting

  1. Reinstall Mac OS X v10.6 (or, for Mac OS X v10.5, perform an archive and install) on your internal hard disk.
  2. Start from the internal hard disk.
  3. Run Software Update.
  4. Install all updates until Software Update reports "Your software is up to date."
  5. Download and install any third-party software updates before reinstalling third-party software, especially drivers and kernel extensions.

    Examples include:

Additional Information

Advanced information about kernel panics and panic logs

You can check kernel panic logs for more information. The kernel panic text is added to the log after you restart the computer, assuming that you did not reset PRAM (the kernel panic text is stored in PRAM until you restart). In Mac OS X v10.6, the logs are located in in /Library/Logs/DiagnosticReports. In Mac OS X v10.5, the logs are located in /Library/Logs/PanicReporter .

Information that may aid developers in the investigation of a software issue may be in the log. The information may also provide a clue as to what event may have caused the kernel panic in the first place. 

Kernel Core Dumps – This technote explains how you can enable remote kernel core dumps used to collect data about the kernel panic.

Understanding and Debugging Kernel Panics – This technote addresses kernel panics: what they are, how to read panic logs and how to debug the code that caused the panic.

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