Mac OSX Troubleshooting

See also

Easy Troubleshooting Steps

Quick, harmless, sometimes can help solve a problem.


Application Troubleshooting:

  • Quit the troublesome app then reopen it. (see below)
  • Quit the program and delete its .plist settings file. This is found either in ~/Library/Preferences or in /Library/Preferences. Deleting it clears all settings for a program, and the program creates a new blank settings file next time you start it up.
  • Create a new user account. Try starting the troublesome app in the new account. If it works fine in the new account try the next tip.
  • Quit the app, move its preference file to the Desktop, reopen the app.
  • Trash the app, trash its preference file. Reinstall the app.
  • Try Software Update

Quitting an application on a Mac

In Mac OSX, closing the window of an application does not quit the application. Look for glowing dots (or black arrows) in front of certain applications in the Dock to see what applications are currently running. To close a running application:

  1. Move your cursor over the Dock icon for the app.
  2. Click and hold down the mouse button. A menu will appear.
  3. Select "Quit" and the application should close. Notice that the "Open" dot or arrow disappears, indicating that the application has been closed.

General OS or boot problems

  • AC Adapter:

Mac laptops usually have a colored indicator where the AC adapter connects to the laptop, this is green when the computer is on, or when the battery is fully charged, or orange when the battery is charging. If no light appears, the charger, laptop or power source are likely faulty.

  • Reset NVRAM:

Shutdown your Mac. Find Command (⌘), Option, P, and R on your keyboard. Turn on your Mac. Press and hold the Command-Option-P-R keys immediately after you hear the startup sound. Hold these keys until the computer restarts and you hear the startup sound for a second time. Release the keys. https://support.apple.com/en-us/HT204063

  • Use Disk Utility First Aid:

From within OS: Follow these steps in OS X: Open Disk Utility, which is in the Utilities folder of your Applications folder. Select the startup disk from the list of volumes. Click the First Aid tab. To check permissions, click Verify Disk Permissions. To repair permissions, click Repair Disk Permissions (applies to OS X Yosemite 10.10 and earlier) https://support.apple.com/en-us/HT201560

From within Recovery Mode: As you Mac restarts, hold down the Command (⌘) – R Select Disk Utility and click Continue In the sidebar, select the volume you wish to repair (Macintosh HD) Click First Aid button Click Repair Disk http://www.idownloadblog.com/2016/02/26/how-to-use-disk-utility-in-mac-recovery-mode/

via Target Disk Mode: Disk First Aid can be run on another drive when connected by Target Disk Mode.

  • Safe Mode Boot: Start or restart your Mac, then immediately press and hold the Shift key. The white Apple logo appears on your display. If you don't see the Apple logo, learn what to do.

Release the shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder. To leave safe mode, restart your Mac without pressing any keys during startup. https://support.apple.com/en-us/HT201262

  • Drain power cache:

Unplug machine after shutting it down. Can sometimes fix a desktop Mac that won't boot.

  • Boot in Verbose mode:

on boot, hold down Apple + V. Watch for errors as Mac boots, and google any errors found.

  • Check Log Files:

Run Console.app to check for recent errors in Mac's log files.

What to do BEFORE doing advanced troubleshooting

  • BACK UP FILES before going on to any of the advanced diagnostics and tricks below. You can use Target Disk Mode (preferred); the Ubuntu live CD also works well with Macs.
  • Before trying these tricks, try installing Combo Pack updates.
  • If you are suspecting/experiencing a system wide issue, always check the hardware diagnostics before taking irreversible action like an OS reinstall.

Hardware troubleshooting with diagnostics

Mac doesn't wake up properly from sleep

See this article for advice: http://www.macfixit.com/article.php?story=20070129234938244

This could be an issue with a corrupt hibernation file. Deleting this file could help. A "clean" sleep/hibernation settings file will be recreated next time the computer goes to sleep. Here's how to delete it (requires admin privileges on the computer):

  1. Login as a user with admin privileges
  2. Open Terminal
  3. Type:
cd /private/var/vm
sudo rm sleepimage

(whoever is logged in, enter your own password when prompted)

  1. Close terminal and restart the computer
  2. Log in as normal and test putting the computer to sleep.

Blinking Question Mark

  • Symptom: Your Mac won't start up. You see a white or gray screen with a blinking/flashing question mark.
  • Cause: The Mac cannot find the operating system. Most likely the hard disk has failed.
  • Solutions: It's worth to try the following:

Recovering Files

If you need to get files from the computer, you can:

  • Try putting the Mac in Target Disk Mode (see below) and connect it to another Mac to copy your files.
    • This may not work, and if it does not, it is an indication that the hard disk has failed completely.
  • If the data on the computer is very valuable, the owner can decide to contact a Professional Data Recovery Service.
  • See below for repair options.


  • College Owned: If the computer is owned by the college, a Helpdesk ticket should be made and the machine should be brought to ITS Service Requests for evaluation, diagnosis, and repair.
  • Personally Owned: The owner must contact Apple Support directly (call 1-800-275-2273) or visit an Apple-authorized repair center, such as the College Bookstore or Small Dog Electronics.

Prevention and safeguards

Hard disks eventually fail, even when best care is taken. The best solution is a robust backup routine including storing files in a secure location such as OneDrive or Google Drive.

For hard drive failure

  • Try Target Disk Mode to repair disk permissions, recover files, etc. (see below)
  • Check the disk integrity.
    1. Boot into Single User Mode by holding down Apple + S on boot.
    2. When system has loaded, enter fsck -fy to check disk.
  • If the OS seems corrupted but the disk is fine, consider Archive + Install. Reinstalls system without touching user files (in theory). A messed-up install might be fixed this way.

Target Disk Mode

Target Disk Mode is a feature of Mac laptops that makes Mac hardware issues much easier to troubleshoot. Basically, a laptop in TDM acts like an external hard drive, which you connect to any other computer using a Firewire cable.

TDM lets you boot a Mac using another Mac's hard drive so you can:

  • Access the internal hard drive without depending on it to boot the system
  • Run Disk Utility to repair disk permissions
  • Run Disk Warrior for advanced repair techniques

Starting TDM

  1. Power up (or shutdown and restart) the Mac.
  2. Immediately after powering on, hold down the t key until the Firewire icon appears on the screen (looks like a windmill).
  3. Now connect the Mac to another Mac using a Firewire cable. The next section explains what you can do with your Mac in TDM.

Uses for TDM

As an external hard drive

When you plug your TDM-Mac into another Mac that is already booted up and running, the TDM-Mac's hard drive will appear in the Finder as an external drive. You can browse it, and manage, copy, and move files as you could with any external drive. This option can also be used for data recovery.

As a bootable device

This is a bit more confusing: you use the computer in TDM as a boot device to start up a Mac system using the TDM hard drive but a different laptop's hardware.

To boot Mac A from Mac B's hard drive using TDM:

    1. Shut down Mac A.
    2. Boot Mac B into TDM and connect the two computers with a Firewire cable.
    3. Power up Mac A and immediately hold down the Option key until a window appears showing boot options.
    4. Select Mac B's hard drive (may be called "External hard drive" or something like that).
    5. Mac A will boot using Mac A's hardware but Mac B's hard disk and software.

This is really useful if you have a problem and you don't know if it's a hardware issue or a software issue. There's also some strange feature of Mac where Mac A's internal hard drive will spin more slowly - and hence, a damaged hard drive won't wear itself out as quickly - when Mac A is booting to Mac B's hard drive using TDM.

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