Nobody ever said the Mac was perfect. (Well, OK, some people do, but you can’t take them seriously.) Macs crash, freeze, refuse to turn on or go online, and generally misbehave just like any other computer, though maybe not as often or as severely.
Hence this two-part guide. We’ll tell you what to do when apps freeze up, when your Mac slows down, when OS X goes into a kernel panic, when the internet refuses to work, and when the Trash refuses to empty. Such crises may be rare, but they do occur and when they do, you want to be prepared.
Last week we brought you the first part of our Mac Emergency feature – split into three. Over the next few days, we bring you part two, again split into three parts. Coming up will be Can’t Get Online and Trash Won’t Empty. But first…
Most crashes on a Mac affect just one application. But you may encounter a type of systemwide crash that brings down your entire Mac: a kernel panic. This occurs without warning, and you can’t save your work or do anything else without restarting. Furthermore, because kernel panics may be due to different causes, you may have trouble diagnosing the problem and preventing its recurrence. BY JOE KISSELL.
Identify it correctly
On systems running OS X 10.7 Lion or earlier, kernel panics usually cause the screen to dim from top to bottom; a message in several languages then appears, telling you to restart your Mac (by holding down the power button for several seconds to turn the computer off, and then pressing it again to turn the system back on).
Starting in OS X 10.8 Mountain Lion, OS X automatically restarts when your Mac suffers a kernel panic; then it displays a message for 60 seconds (or until you press a key) informing you that your Mac restarted because of a problem. (If, however, 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 for dealing with kernel panics (support.apple.com/kb/ TS3742), something as random and fleeting as malformed network packets or simply the use of out-of-date software can cause a kernel panic. So, for those of you who experience this problem just the once, or only rarely, your best bet is to restart the machine, get back to work and forget about it.
But if you encounter kernel panics frequently (apparently Apple defines ‘frequently’ as “more than once every few weeks”), you should take additional troubleshooting steps. The sequence of steps that we recommend here differs somewhat from the sequence that Apple outlines.
Reopen your apps
If you’re running OS X 10.8 or later, immediately after your Mac restarts on its own, you’ll see a dialogue box asking whether to reopen the apps that were open before the crash happened. Click Open.
If the kernel panic recurs, the likely culprit is one of the running programs, so click Cancel the next time around. Either way, another dialogue box will ask if you want to see more information and report the problem to Apple. You probably do, so click Report. You may not be able to make any sense of the technical details, but glance over them and then click OK to send the report to Apple. If you run into kernel panics repeatedly, you will just have to roll up your sleeves and do some serious troubleshooting to get rid of them permanently.
Restart your Mac and hold down the Shift key until you see the grey Apple logo. Taking this action temporarily disables some software that may be causing problems, and it also directs your system to run some cleanup processes. If the kernel panic doesn’t recur in this mode, restart your Mac normally.
Update your software
Outdated software is often implicated in kernel panics. Possible culprits include OS X itself and (very rarely) regular applications. More commonly, the underlying problem relates to low-level software such as kernel extensions and drivers.
If you’ve installed software that works with peripherals (network adapters, audio interfaces, graphics cards, input devices or the like) or antivirus, file-system or screen-capture tools, check for newer versions. To update OS X, Apple apps and items purchased from the Mac App Store, select Software Update from the Apple menu; for other apps, use a built-in updater or check the developer’s website.
Update your firmware
Software Update may also notify you of available firmware updates for your Mac. If so, be sure to install them. Another option is to check for firmware updates that are applicable to your Mac model at (support. apple.com/kb/ht1237).
Check your disk
Make sure that your startup disk has at least 10GB of free space. If it does not, delete some files to make room. Next, you’ll want to find and fix any disk errors. Start from another volume, run Disk Utility, select your startup disk and click Repair Disk. If you’re running OS X 10.7 or later, the easiest way to do this is to restart and then immediately afterward press and hold c-R to enter OS X Recovery. If that doesn’t work, or if you have an older Mac, you can start up from a bootable duplicate of your hard disk or your OS X install media.
Check your peripherals
If kernel panics continue to plague your computer, shut down the Mac and disconnect everything except the bare minimum items (keyboard, pointing device and display, if those pieces aren’t built in) – including any hardware you’ve added inside your Mac, such as a graphics card. Then turn your system back on.
If the problem doesn’t reappear at this point, shut down your system a second time, reattach one device, and restart. Repeat the process for each device in your setup. If you see a kernel panic immediately after connecting a piece of hardware, that device may be the problem.
Check your RAM
Defective RAM can cause kernel panics – and unfortunately the defects sometimes manifest themselves only after an interval of time has passed following their installation. If you’ve added any after-market RAM to your Mac, try turning off your system, removing the additional RAM and restarting. If that operation makes the kernel panics vanish, contact the company that sold you the RAM to see about a warranty replacement.
Consult a Genius
After you’ve exhausted all of the preceding options, the troubleshooting steps that remain to be tried get more time-consuming – enough so that, if we got to this point with no end in sight, we’d think about setting up an appointment at the nearest Genius Bar.
Reinstall OS X
Have a spare hard drive at your disposal? You can try installing a fresh copy of OS X on it, booting from that drive and running Software Update to ensure that everything on the system you’re working with is current. If the kernel panic doesn’t occur when you run your Mac from that extra drive, you can be fairly certain that you’re dealing with a software issue – in all likelihood some obscure gremlin lurking on your startup disk.
It won’t please you to learn that the easiest solution is to start up from another volume (or use OS X Recovery) and then reinstall OS X over your existing Mac. Worse, if that procedure doesn’t work, the next step is to erase the disk and reinstall everything from scratch.
by Joe Kissell