Mac Troubleshooting

This is meant to be a quick and dirty troubleshooting guide for Macintosh computers running OS X. It is not meant to be a fix-all, some issues may not fall into the scope of this document, but it’s a good list of troubleshooting steps to be familiar with. The steps are listed in the order in which you should generally take them to solve an issue.

Click on each step for more detail. Take notes on what you do and the results of each step; this can be useful for Apple if you have to call them as a last resort. And before you remove anything, or get into the heavier troubleshooting, always remember to backup the Mac first!

Also, read each part completely before doing it and for example don’t try hardware troubleshooting if you’re having a specific issue with an application. You’re wasting your own time and can end up causing other issues.

General Troubleshooting

  1. Restart
  2. Check/fix the filesystem
  3. Clear system & user caches
  4. Create a new user account, and see if the problem persists there
  5. Check for interfering/unwanted applications
  6. Startup in SafeBoot mode, and see if the problem persists there, or afterwards
  7. Check system resources
  8. Reinstall the affected application
  9. Unplug all USB, Firewire devices except Apple mouse

More Serious Issues

  1. Check the System Logs
  2. Repair permissions
  3. Reapply the latest combo updater
  4. Run the Apple hardware CD/DVD and Apple Service Diagnostic CD
  5. Check the hard drive for bad blocks
  6. Check RAM
  7. Reset PRAM/NVRAM
  8. Reset PMU
  9. Boot from External Drive
  10. Rebuild OS
  11. Call Apple

If possible, restart from inside the OS, usually by clicking on the Apple Menu in the top left, and selecting “Restart”. If this is not possible, hold down the power button on the machine for 5 seconds. If this does not work, unplug the power cord and remove the battery, if it’s a laptop.

If you had to force the system to shut down, but it appears to be working afterwards, still do some of the following checks. Having to force shut down a machine can be a indicator of more serious issues.

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Check/fix the filesystem
There are many different ways to do this. You can boot off the OS X Installation CD/DVD, run Disk Utility, and select Repair Disk. If you don’t have access to the Installation disc, you can also run AppleJack, or the UNIX command “fsck”, from the Terminal in Single User Mode. You can boot into Single User Mode by holding down Command-S at system startup. Follow the prompts to run AppleJack or fsck respectively.

Disk Utility will report back whether or not there were any problems, and whether or not it could fix any problems. If it is unable to fix a problem, then skip down to the hardware/filesystem tests.

If there were errors that needed to be fixed, and your software reports that they were all successfully fixed, you may have solved your problem, but you should check it with the 3rd party tests to make sure.

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Clear System and User Caches
When the OS is running, caches of files/databases are created in order to speed things up the next time they’re used. Sometimes they can become corrupted and cause all sorts of issues.

Use AppleJack, Maintain or Onyx, to clear these caches.

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Try a New User Account
Create a new user account, and see if the problem persists there. This will tell you if it’s a specific problem with the user account or with the system as a whole.

You do this by creating a new user in the Accounts tab of System Preferences, logging out, and logging into the new account. If this makes the problem go away, it means the cause is in the user’s account.

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Check for Interfering/Unwanted Programs
Sometimes the user can download/install programs that will wreck the rest of the system. Some examples of this include:

  • Application Enhancer
    • Sits in System Preferences, adds ‘features’ to the OS. Can cause major issues with other programs. Disable any modules, reboot, then remove the Preference Pane from the ~/Library/Preference Panes folder or the /Library/Preference Panes folder.
  • Any Norton Application
    • Like it’s Window’s counterpart, Norton for the Mac is pretty useless and only serves to crash, corrupt, and otherwise mess up any Mac it touches. Remove it.
  • Any two Antivirus programs.
    • Again, like Windows, running two antivirus programs can cause issues. Remove one.

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Start the machine in Safe Boot Mode
Safe Mode on a Mac has it’s own page here. If the doesn’t persist in Safe Mode, it can be a font or third-party extension causing your issue.

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Check the System Resources
If a user is complaining about slowness or constant “spinning beachballs” when they try to do something, it could be a issue with a particular program hogging system resources, and thus slowing down the rest of the machine.

For example, when the system is running out of memory, it needs to write swapfiles to the hard drive. If your hard drive is almost full, then the system will bog down to a point where it isn’t usable because the OS has to constantly write/read swap files. Keep tabs on how much free space you have on your boot disk by getting info (Command-i) on that disk in the Finder.

You should have at least 1GB to 3GB of free space at all times. Realistically you would want more than that, especially if you plan on burning CD/DVD’s. Remember that even if you have more free space than this when you first booted, swapfiles can eat up disk space quickly – 10GB or more of swapfiles is not unheard of. So it’s a good idea to have at least 5GB of free space immediately after booting.

Trash unneeded files and applications to free space. Tell the user to store more documents on the external/network drives and use them directly in that location or only copy them down when they need it, then copy them back up when finished. You can also try Delocalizer, this program will go through and only keep American English, and whatever others you specify, and can save as much as a gig of space. Suggesting more RAM is another good solution, but may not be possible/practical in all situations. Restarting will temporarily get rid of all swapfiles, but they’ll come back.

You can can check Memory, CPU, and Disk usage, as well as network usage, in the Activity Monitor. Located in /Applications/Utilities, this can help narrow down an application that’s hogging the CPU or memory.

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Clean/Reinstall/Update the Affected Application
If you’re having a specific problem with an application, try to remove the preference files, as they can become corrupted. On a Mac, they’re usually located in ~/Library/Preferences and have a .plist extension. Move the file in question out of the directory, and relaunch the application. The preference file will be recreated by the program when it’s opened. Microsoft Office stores it’s preferences in ~/Documents/Microsoft User Data/; this includes the Entourage email database.

If that doesn’t work, reinstall the application. This can be done by removing the application from the /Applications folder, as well as the corresponding preference file(s), and simply following the application specific instructions for reinstalling.

As a note, applications that interact heavily with the OS, such as the CiscoVPN client, install a lot of files in the /Libray and /System/Library folders. If the program does not contain an uninstaller, ask someone who knows for a list of the files that it installs or look in the installer itself for a list.

It can also be as simple as updating an app to fix a nasty bug, help to conform to OS compatibility, or make it Intel compatible (if you have an Intel Mac.) Most application versions can be found by going to the Application menu at the top left and going to “About” or by getting info on the actual application in the Finder. Check,, or the developer’s website for the latest updates.

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Unplug all 3rd party USB, FireWire, PCI devices except the Apple mouse.
Shut down the machine and then reboot with everything unplugged, including PCI cards if it’s a desktop, minus the video card of course. If this makes the problem go away, then you have a bad external device, bad cable, or bad port on your computer. Try to isolate which one it is. Be especially wary of USB hubs and unpowered USB/FireWire devices.

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More Serious Issues

Check the System/Application Logs
Inside of the /Applications/Utility folder is a handy little App called Console. This will easily allow you to view all the logs on the system, be it a generic system log, a log specific to an application or a kernel panic log. Sometimes these can be very helpful in diagnosing an issue. Sometimes it can just be gibberish. Use your judgment don’t be afraid to post the log somewhere and ask, there are many knowledgeable folks out there.

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Repair Permissions
Each file in the Mac system is assigned a proper permission. This ensures that the proper applications can access what they need to, that the user has access to what they should, and can’t break very important things, like the admin user, kernel, etc. System permissions can, though it’s unlikely in 10.3 or higher, get altered when applications are installed/executed or updates are applied. Incorrect permissions can cause all sorts of errors, application/OS crashes, strange file behavior, etc.

Running the Repair Permissions tool will ONLY check Apple installed applications, system files, and applications installed via an actual Apple Installer that leaves a receipt in /Library/Receipts. So your favorite foxy web browser? Won’t help a bit cause all you did was drag it to your Applications folder. It won’t help with all those crazy permissions you custom set in your home directory either.

Also, as John Gruber points out, repairing permissions will not fix most issues. It is for a specific purpose and specific troubleshooting.

Run this in Disk Utility in the affected user’s login. Open Disk Utility in the \Applications\Utilities folder. Select the boot drive (probably “Macintosh HD”), click on the First Aid tab and click the Repair Permissions button. You can also do this when booting from the installation CD/DVD or using AppleJack in Single User Mode.

Always run a ‘Verify’ first. If the reported issues have no bearing on what the trouble you’re seeing actually is, don’t fix them. They’re not the issue, look somewhere else.

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Reapply the latest combo updater
Download the latest OS X updater from Apple. These updates come in 2 flavors, an updater which will only update the next most recent version of the OS, and a combo updater, which will update all versions since the last main update (10.1, 10.2, etc.). You want the combo updater. It will be labeled as the combo updater, and it will be much larger than the normal updaters – pay attention to `PPC vs. Intel too, they’re labeled.

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Run the Apple Hardware Diagnostic CD/DVD and Apple Service Diagnostic CD
The Apple Hardware Diagnostic CD/DVD comes with every new Mac and can be useful in determining hardware problems with various parts of your system. Start with the Hardware Diagnostic CD/DVD, as this checks the Hard Drive.

If you have access to Apple Service Diagnostic CD’s, try them too. They’ll run some more in-depth tests on the system and can help pinpoint direct issues. Sadly, these are only available to Apple Service Tech’s.

You can also try Disk Warrior, available here. This is useful for a last step before testing hardware issues. Disk Warrior checks directory structure and can rebuild a fragmented or corrupt directory tree and solve many issues. Version 3.0.3 of Disk Warrior NOT Intel compatible. The latest version, 4.0, is Intel compatible. )

Some notes about Apple Diagnostic Discs:

  • The newer machines come with a diagnostic partition built into the restore DVD’s. Look on the front of the first DVD for more info.
  • You can run the tests in loops to ramp up processor/memory/hard drive usage if the issue is intermittent.
  • Certain discs will only work for certain models.

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Check the hard drive for bad blocks
You can use TechTool Pro, available here, to boot the system and run several hardware tests, including a sector scan of the drive. Hearing odd noises coming from your drive is another tip-off that this may be your trouble.

Tech Tool Pro, version 4.0, does not work properly with Intel machines and it’s block scanning feature does not report accurately for SATA drives. Version 4.5 fixes these issues.

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Take out 3rd party RAM
Non Apple approved RAM can cause all sorts of issues with Apple machines. From system crashes to odd application behavior, bad RAM is bad news. Use standard techniques (swapping, etc), to test the RAM and RAM slots.

Also, while the Apple Hardware tests can indeed do RAM testing; along with TechTool Pro; the best way to test memory on a Mac is using Memtest. It’s not free, but pretty close to it. It’ll do a much more extensive memory test than either the Apple or TechTool tests.

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Reset the machine’s PRAM/NVRAM
PRAM stores certain system and device settings in a location that Mac OS X can access quickly. Exactly which settings are stored in the computer’s PRAM varies depending on the type of computer as well as the types of devices and drives connected to the computer.

Zapping the PRAM is useful to troubleshoot booting issues, and that’s pretty much it. If you’re not experiencing any issues with startup, don’t do it.

Some information stored in PRAM includes:

  • Display and video settings such as refresh rate, screen resolution, number of colors
  • Time zone setting
  • Startup volume choice
  • Speaker volume
  • Recent kernel panic information, if any
  • DVD region setting

Note: Mac OS X stores your preselected DVD region choice in PRAM for easy access. Resetting PRAM does not allow you to change the DVD region.

Unlike prior versions of the Mac OS, Mac OS X does not store network settings in PRAM. If you experience a network issue, resetting PRAM will not help. If PRAM is reset, you may need to verify your time zone, startup volume, and volume settings using System Preferences. Certain firmware updates may reset PRAM as a normal part of their installation process.

  1. Shut down the computer.
  2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
  3. Turn on the computer.
  4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
  5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
  6. Release the keys.

Your computer’s PRAM and the NVRAM are reset to the default values. The clock settings may be reset to a default date on some models.

If your computer does not retain parameter RAM (PRAM) settings when it is turned off, this generally indicates that the battery needs to be changed. Some Macintosh models may display a black screen when you turn them on if the battery needs to be changed.

Some Macintosh computers have a backup battery to maintain system settings, such as the date and time, when the computer is turned off. The battery may last up to five years. However, this varies due to the battery’s shelf life, and usage patterns of the computer. The batteries used in Macintosh computers are lithium or alkaline, and are commonly 3.6 V to 4.5 V.

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Reset the Power Management Unit (PMU)
The PMU’s location, and how to reset it, varies by machine. It’s can also be referred to as the SMC (System Management Controller) Look at the links below for specific machine instructions:

See if this cures the problem. Typically this will fix issues when your system will not power on.

Same rules apply to the PMU that apply to the PRAM. If you’re not having power issues with the machine, DON’T DO IT. You risk serious damage to the machine for something that you know will not have any effect on solving the problem.

Make sure you only hold in the PMU button for a second. DO NOT hold it in for any longer and DO NOT press it more than once. If you do this it could result in corrupting the PMU itself.

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Boot from an External Drive
If it’s an issue with the Hard Drive, the cable, IDE channel, or something similar, it can be useful to boot from an external drive, via firewire, and run diagnostics from there. To do this, connect the drive via firewire and make sure it has power. Boot the machine holding down Option and then select the firewire drive as the boot device.

The boot and general usage will be slightly slower than using the internal drive, however it should be usable.

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Rebuild the OS
If you’ve tried all the above, follow the steps on the Rebuild page to rebuild the OS on the machine.

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Call Apple
At this point, if you can’t confirm a hardware issue, and you’ve rebuilt the OS from a clean image, it’s probably time to call Apple and see what they have to say. Have a list ready of the steps you’ve taken already to resolve the issue, as well as symptoms and how to reproduce the issue..

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Useful Links

This list was refined from a list made from the contributions of many folks at to work with current Apple and Third-Party hardware/software. Josh Bierman and Alan Henry also contributed.

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