New Users (3): The Kernel Panic: Something Many Users will Never See

By Graham K. Rogers


While I was thinking about how new users deal with the move to OS X, one wrote to me with a question: What is a Kernel Panic? The Kernel is the core of the operating system, linking the computer's hardware components to the software.

In most cases everything will be running fine, but sometimes a problem or conflict can be introduced and the system becomes confused. Nine times out of ten if the problem is software, the offending application will usually figure out the problem or quit by itself. Some conflicts are hardware related, and in my experience RAM has often been a cause: that cheap memory may prove to be more expensive in the long run. Other difficulties have been caused by printer or mouse drivers and by changes to third party software. To see a full explanation and several suggestions I urge users to look at Dr. Smoke's XLab FAQs and to buy his related, online book: Troubleshooting Mac OS X.

What the user sees, if ever a kernel panic (KP) occurs, can be manifested in a couple of ways. Least likely these days is that the screen changes to black with white letters, perhaps showing some obscure messages, for example, "We are all hanging here". These days, the KP will probably appear like a dark curtain descending slowly over the screen. A black panel in the middle will appear with multi-language instructions to restart the computer.

Not a real KP - an emulation

When I replied to that email, the writer added, "Let's hope and pray this never happens." I agree, but this indicated that he was bringing to his new Mac use a certain level of paranoia: he was expecting problems to occur, which may be a remnant of previous computing experiences.

With my current computers, I have seen two KPs on the MacBook Pro, which I have been using constantly -- day in, day out -- for the last 3 years. My iMac which is about 2 years old and is also used daily, has had none. Other users are not so fortunate, but I take care (and read Dr. Smoke's suggestions), while also experimenting with a lot of new software. Preparation is the key as we suggested in Part 1 (31 March). Preventative maintenance is part of that preparation.

In many cases, restarting the computer will allow a user to get back to work with no more interruptions. However, I feel that, even in these minor cases, a Safe Start (hold down the Shift key) would be better first, then a restart.

One of the most important things for a user with a Kernel Panic to do after shutting the computer down is not to panic. Try to remember what changes (if any) had been made recently, particularly in the last hours; or what actions were being carried out at the time of the KP. If, for example, a large file was being processed at the time, actions of the Finder and other applications all trying to work at the same time (while unusual) may have triggered the situation. If the computer had been dropped, displacing RAM; or a RAM module had been changed, this might also upset things.

If the KP returns, further investigation is needed. Returning the computer to the state before the KP (such as removing new RAM), may stop the problem. Another place to start looking is in Console and an expert, such as on the Apple User Forums, would be able to interpret the crash logs.

Repairing Permissions

On a restart after a KP, a more prudent user might want to make further checks, for example by using the Repair Permissions facility in Disk Utility. While this carries out its tasks, the main panel will show many indications where changes are made to files (or not made). This is normal and a new user should not be discouraged by the amount of text there. A lot of the information shown is normal, but this tends to worry new users. There are also likely to be more entries after an update, for example the recent 10.6.3 download.

Software Update - 10.6.3 and Others

With a KP, it is also a good idea to carry out a repair, by starting with the grey installation disks; always keep these safe. After selecting the language, we use the Utilities menu to access Disk Utility on the disk. A stronger utility, like Disk Warrior or Tech Tool Deluxe, might also be used and any repairs noted. TechTool Deluxe comes with AppleCare and is useful for diagnosing and testing critical system hardware components. It will not be able to repair disk directory problems. For that I would use Disk Warrior.

I have a screen shot of a Kernel Panic (above). This is not a real one, but comes from a utility (Panic 2.0.1) written expressly for the purpose. I use it to show students. In the majority of cases, this demonstration is the closest most ever come to seeing this.

See Also:

  • New Users (1): Use of Accounts and Passwords
  • New Users (2): Disk Contents and Some Pitfalls for New Users of OS X
  • New Users (4): Preventative Maintenance and Disk Warrior
  • New Users (5): Some Utilities for OS X
  • New Users (6): Some more useful utilities
  • New Users (7): A Few More Useful Maintenance Utilities
  • New Users (8): Some Suggestions for Guarding Against Malware on Macs

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