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Troubleshoot a kernel panic

By Joe Kissell, Macworld
February 06, 2013 01:55 PM ET

Macworld - Most crashes on a Mac affect just one application. But you may encounter a type of system-wide crash that brings down your entire Mac: a kernel panic. When this occurs, there's no warning and no way to save your work or do anything else without restarting. And, because kernel panics can have many different causes, diagnosing the problem and preventing its recurrence are difficult.

How do you know if it's a kernel panic?

If you're running OS X 10.7 Lion or earlier, kernel panics usually result in your screen dimming from top to bottom, and a message appearing in several languages telling you that you must restart your Mac (by holding down the power button for several seconds to turn it off, and then pressing it again to turn it back on).

Starting in OS X 10.8 Mountain Lion, OS X automatically restarts when you have a kernel panic, and then displays a similar-looking message for 60 seconds (or until you press a key) telling you that your Mac was restarted because of a problem. (If the kernel panic repeats every time your Mac restarts, OS X will give up after five tries and shut your Mac down.)

As Apple notes on its support page about kernel panics, something as random and fleeting as malformed network packets can potentially cause a kernel panic. So, if you experience this problem just once, or only rarely, just restart, get back to work, and forget about it.

But if you see a kernel panic frequently (Apple apparently defines "frequently" as "more than once every few weeks"), you should take additional troubleshooting steps. I suggest a slightly different sequence of steps than what Apple outlines.

First things first

If you're running OS X 10.8 or later, immediately after your Mac restarts on its own you'll see a dialog box asking whether you want to reopen the apps that were open before the crash. Click Open; if the kernel panic recurs, one of the running apps is a likely culprit, so click Cancel the next time around. Either way, another dialog box will ask if you want to see more information and report the problem to Apple. You probably do, so click Report. You may be unable to make heads or tails of the technical details, but glance over them and then click OK to send the report to Apple.

If you're seeing repeated kernel panics, try the following things until they go away.

Do a safe boot: Restart your Mac and hold down the Shift key until you see the gray Apple logo. Doing so temporarily disables some software that could cause problems and runs some cleanup processes. If the kernel panic doesn't recur, restart again normally.

Update your software: Outdated software is frequently implicated in kernel panics. This may include OS X itself and, very rarely, regular applications. More often it involves low-level software like kernel extensions and drivers. If you've installed software that goes with peripherals (network adapters, audio interfaces, graphics cards, input devices, etc.) or antivirus, file-system, or screen-capture tools, those should be the first you check for newer versions. Choose Software Update from the Apple menu to update OS X, Apple apps, and items purchased from the Mac App Store; for other apps, use a built-in updater or check the developer's website.

Originally published on www.macworld.com. Click here to read the original story.

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