OSX: Troubleshooting Tips: start-up Issues

Please note: This support document is intended for all-staff use to provide troubleshooting tips that computer issues that occur during computer start-up. Tips require administrative login.

During computer start-up, sometimes the start-up process hangs on a blue or gray screen, a broken folder, a kernel panic, a flashing question mark, or some other start-up anomaly. These types of issues can be simple to resolve, and the following tips may help to do so.

Mac won't turn on

If the computer won't turn on—you don't hear a start-up sound or any fan or drive noise—try the following steps, one-by-one.

  1. Make sure that the power cord is plugged into a working electrical outlet (to confirm that an electrical socket is working, plug in a lamp or other electric device and turn it on).
  2. Make sure that the power cord is properly connected to both your computer and the electrical outlet (if using a power strip, verify that the strip is powered on).
  3. Try plugging a different power cord into the computer, if you have a working one available. If the computer starts up, replace the old power cord.
  4. Disconnect all devices, except for the keyboard and mouse, that are plugged into your computer (i.e., printer, hub, iPod, etc.), and try turning on the computer again.
  5. If you have an iBook, PowerBook, or Mac mini, try starting up your computer by pressing the Control-Apple-Power Button keys simultaneously.
  6. If you have an iBook or PowerBook, make sure that the computer battery has enough charge to start-up—plugging in the power adapter will allow you to start-up the computer if the battery has no charge.

Your Mac starts up and then stops on a start-up screen

 If the start-up process stops on an empty, blue or gray screen or a screen with a progress indicator, try the following techniques, one-by-one.

  1. Incompatible third-party start-up item. Temporarily disable start-up items to see if the computer will then start-up normally:
  1. Shutdown your computer.
  2. Press the Power Button and immediately press and hold the Shift key to start-up in Safe Mode. When you see the "Safe Boot" screen, let go of the Shift key.
  3. When your computer finishes start-up, drag any third-party items out of the /Library/StartupItems and /System/Library/StartupItems folders. Restart the computer to see if it starts up normally.
  1. Incompatible login item could be causing the problem. Remove the login items to see if the computer will then start-up normally:
  1. Shutdown your computer.
  2. Press the Power Button and immediately press and hold the Shift key to start-up in Safe Mode. When you see the "Safe Boot" screen, let go of the Shift key.
  3. When the computer finishes start-up, choose System Preferences from the Apple menu and click Accounts. Click the Login Items tab; select all login items and remove them by clicking the minus (-) button.
  4. Restart your computer to see if it starts up normally
  1. Bad Ethernet cable? Temporarily disconnect it, then restart the computer to see if it starts up normally. If start-up is normal, replace the bad cable.

Your Mac starts up with a dark text screen or a bunch of gibberish text (kernel panic)

During start-up, a dark text screen with the message, "You need to restart your computer" in several different languages may display. This is known as a kernel panic, a type of error message that can be caused by damaged or incompatible software or hardware. A kernel panic error message can also display as white gibberish text against black text fields on top of your Desktop picture.

In most cases, the kernel panic can be resolved by simply restarting your computer (press and hold the Power Button until the computer shuts down, wait ten seconds, then press the Power Button to start-up again).

If the problem continues to recur, following are some troubleshooting tips to try:

  1. First, determine what you did before the kernel panic occurred: Did you install new software or new memory? Did you see an alert or error message causing you to restart your computer? Did an application stop responding necessitating you restart the computer?
  2. If you installed any new hardware (i.e., printer, hub, external drive, etc.), shutdown the computer, disconnect the new device, and restart the computer. If start-up is normal, it’s possible a new driver is causing the issue; see the next step outlining how to remove the software to see if that resolves the issue.
  3. If you installed new third-party software, try uninstalling it by doing the following:
  1. Restart the computer and immediately press and hold the Shift key while your computer starts up until you see the "Safe Boot" screen.
  2. Use the third-party software's original installer to uninstall the recently installed software, or do a search (Apple-F keys in the Finder) to locate the software and any related preference files, drivers, etc., and move those items to the Trash.
  1. Damaged start-up or login items can also cause kernel panics. To troubleshoot these items:
  1. a. Restart the computer and immediately press and hold the Shift key to start-up in Safe Mode. 
  2. From the Apple menu, choose System Preferences. Click Accounts, then select the Login Items tab
  3. Note what login (start-up) items, if any, are listed. Next select all items listed and click the minus sign (-) button to remove them.
  4. Restart the computer. If start-up is normal, add the start-up items back to your Login Items list one-at-a-time while logging out and back in each time to test. If the issue recurs, the last item you added is the culprit.

Mac displays a blinking icon at start-up

Sometimes on start-up, the computer may display nothing but a blinking question mark or a blinking globe icon indicating that the computer can't find the system software it needs to start-up. The problem may be momentary and then start-up will continue, or perhaps the computer won’t complete start-up at all. Usually all that is necessary is to remind Mac where its system software resides. Here’s some tips to try:

Mac starts up normally, but after a brief delay

a. From the Apple menu, choose System Preferences, and select Start-up Disk.

b. In the resulting panel, select the Mac OSX volume, and restart the computer.

If you still see a blinking question mark or globe, try this:

  1. Restart the computer and immediately press and hold the X key.
  2. Your computer will start-up to a gray screen and then restart again.
  3. Let go of the X key after the computer starts up the second time.

If that doesn't work, try resetting your computer's PRAM (parameter random access memory), then repeating the X key steps above afterwards.

  1. Restart the computer and immediately press and hold the Apple-Option-P-R keys simultaneously before the gray screen appears.
  2. Continue holding these four keys until you hear the start-up sound for the second time.
  3. Release the keys to allow your computer to start-up normally.