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computer will not boot

522 Views 3 Replies Latest reply: Jan 6, 2013 11:16 AM by Linc Davis RSS
petguest Calculating status...
Currently Being Moderated
Jan 6, 2013 3:12 AM

I have reinstalled the operating system and software and them recovered user settings fro time machine. It was working ok but after trying to startup today it will not boot (grey scree, apple and grey time scroll). I have started it externally from a USB stick and performed disc utilities and reinstalled the OS but it still will not boot. I would prefer not to wipe the hard drive and start again. Is there some way of forcing the computer to boot?

MacBook Pro, OS X Mountain Lion (10.8.2)
  • Radiation Mac Level 5 Level 5 (4,630 points)
    Currently Being Moderated
    Jan 6, 2013 3:37 AM (in response to petguest)

    I would first reset the PRAM and SMC:

     

     

    Resetting the System Management Controller (SMC)

    Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).

    1. Shut down the computer.
    2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
    3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
    4. Release all the keys and the power button at the same time.
    5. Press the power button to turn on the computer. 
      Note
      : The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

    Resetting NVRAM / PRAM

    1. Shut down your Mac.
    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 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.

    If those don't solve it, then I would do a Safe Boot:

     

    To perform a Safe Boot, press and hold the Shift key immediately after your Mac starts up. Continue holding down the Shift key until a gray Apple logo appears on the screen.  Here's further info on Safe Boot:

     

    http://support.apple.com/kb/HT1564

  • Linc Davis Level 10 Level 10 (107,825 points)
    Currently Being Moderated
    Jan 6, 2013 11:16 AM (in response to petguest)

    Take each of these steps that you haven't already tried. Stop when the problem is resolved.

       
    Step 1
        
    The first step in dealing with a boot failure is to secure your data. If you want to preserve the contents of the startup drive, and you don't already have at least one current backup, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data that has changed since your last backup, you can skip this step.

     

    There are several ways to back up a Mac that is unable to boot. You need an external hard drive to hold the backup data.

    a. Boot into Recovery by holding down the key combination command-R at the startup chime, or from a local Time Machine backup volume (option key at startup.) Release the keys when you see a gray screen with a spinning dial. When the OS X Utilities screen appears, launch Disk Utility and follow the instructions in the support article linked below, under “Instructions for backing up to an external hard disk via Disk Utility.”

    How to back up and restore your files

    b. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, boot the non-working Mac in target disk mode by holding down the key combination command-T at the startup chime. Connect the two Macs with a FireWire or Thunderbolt cable. The internal drive of the machine running in target mode will mount as an external drive on the other machine. Copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.

    How to use and troubleshoot FireWire target disk mode

    c. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.

    Step 2

    Press and hold the power button until the power shuts off. Disconnect all wired peripherals except those needed to boot, and remove all aftermarket expansion cards. Use a different keyboard and/or mouse, if those devices are wired. If you can boot now, one of the devices you disconnected, or a combination of them, is causing the problem. Finding out which one is a process of elimination.

    Before reconnecting an external storage device, make sure that your internal boot volume is selected in the Startup Disk pane of System Preferences.

    Step 3

     

    Boot in safe mode.* The instructions provided by Apple are as follows:

     

    • Shut down your computer, wait 30 seconds, and then hold down the shift key while pressing the power button.
    • When you see the gray Apple logo, release the shift key.
    • If you are prompted to log in, type your password, and then hold down the shift key again as you click Log in.

     

    Safe mode is much slower to boot and run than normal, and some things won’t work at all, including wireless networking on certain Macs.

     

    The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

     

    *Note: If FileVault is enabled, or if a firmware password is set, or if the boot volume is a software RAID, you can’t boot in safe mode. Post for further instructions.

     

    When you boot in safe mode, it's normal to see a dark gray progress bar on a light gray background. If the progress bar gets stuck for more than a few minutes, or if the system shuts down automatically while the progress bar is displayed, your boot volume is damaged and the drive is probably malfunctioning. In that case, go to step 5.

     

    If you can boot and log in now, empty the Trash, and then open the Finder Info window on your boot volume ("Macintosh HD," unless you gave it a different name.) Check that you have at least 9 GB of available space, as shown in the window. If you don't, copy as many files as necessary to another volume (not another folder on the same volume) and delete the originals. Deletion isn't complete until you empty the Trash again. Do this until the available space is more than 9 GB. Then reboot as usual (i.e., not in safe mode.)

     

    If the boot process hangs again, the problem is likely caused by a third-party system modification that you installed. Post for further instructions.

     

    Step 4

     

    Sometimes a boot failure can be resolved by resetting the NVRAM.

     

    Step 5

     

    Launch Disk Utility in Recovery mode (see above for instructions.) Select your startup volume, then run Repair Disk. If any problems are found, repeat until clear. If Disk Utility reports that the volume can't be repaired, the drive has malfunctioned and should be replaced. You might choose to tolerate one such malfunction in the life of the drive. In that case, erase the volume and restore from a backup. If the same thing ever happens again, replace the drive immediately.

     

    This is one of the rare situations in which you should also run Repair Permissions, ignoring the false warnings it produces. Look for the line "Permissions repaired successfully" at the end of the output. Then reboot as usual.

     

    Step 6

     

    Boot into Recovery again. When the OS X Utilities screen appears, follow the prompts to reinstall the OS. If your Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade.

     

    Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.

     

    Step 7

     

    Repeat step 6, but this time erase the boot volume in Disk Utility before installing. The system should automatically reboot into the Setup Assistant. Follow the prompts to transfer your data from a backup.

     

    Step 8

     

    If you get this far, you're probably dealing with a hardware fault. Make a "Genius" appointment at an Apple Store to have the machine tested.

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