iMac shuts down on 1/3 of boot sequence

OS X Mavericks- If your computer stops or delays while starting up with progress bar

OS X v10.6- Gray progress bar appears under Apple logo during startup

What version of OS X do you have installed?

Reinstalling OS X Without Erasing the Drive

Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Reinstalling OS X Without Erasing the Drive

Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.

When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list. Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu.

Reinstall OS X: Select Reinstall OS X and click on the Continue button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

Also see:

Reinstall OS X Without Erasing the Drive

Choose the version you have installed now:

OS X Yosemite- Reinstall OS X

OS X Mavericks- Reinstall OS X

OS X Mountain Lion- Reinstall OS X

OS X Lion- Reinstall Mac OS X

Note: You will need an active Internet connection. I suggest using Ethernet

if possible because it is three times faster than wireless.

After updating and rebooting, I am experiencing the EXACT same problem. 2009 27" iMac, Intel too!

Then I recommend a clean install:

Install or Reinstall OS X from Scratch

Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.

Boot to the Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Erase the hard drive:

1. Select Disk Utility from the main menu and click on the Continue button.

2. After DU loads select your startup volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.

3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.

4. Quit DU and return to the main menu.

Reinstall OS X: Select Reinstall OS X and click on the Install button.

Note: You will need an active Internet connection. I suggest using Ethernet if possible

because it is three times faster than wireless.

This should install the version of OS X that you had installed.

Hi, I have the exact same problem.

The disks are checked and fine. but the logfile below says different.

Does any one have a solution?

Thx.

I have the full crash-logfile if needed.

Sep 5 06:01:30 localhost OSInstaller[387]: Setting external root to: /

Sep 5 06:01:30 localhost OSInstaller[387]: OSI: com.apple.pkg.BaseSystemResources remapped external root path to: /

Sep 5 06:01:30 localhost OSInstaller[387]: Total install size including padding: 8272177152 b + 0 b non-OS collection items

Sep 5 06:01:30 localhost OSInstaller[387]: Can not connect to /var/run/systemkeychaincheck.socket: No such file or directory

Sep 5 06:01:31 localhost OSInstaller[387]: PK will install signed package file:///Volumes/Macintosh%20HD/OS%20X%20Install%20Data/OSX_10_9_IncompatibleApp List.pkg

Sep 5 06:01:31 localhost OSInstaller[387]: PFPackage::packageWithURL - can't instantiate package: /System/Installation/Packages/OSInstall.mpkg

Sep 5 06:01:31 localhost OSInstaller[387]: Error opening package "OSInstall.mpkg".

Sep 5 06:01:31 localhost OSInstaller[387]: X Source too new: Source version: 10.10, Destination version: 10.9.5

Sep 5 06:01:31 localhost OSInstaller[387]: Starting installation:

Sep 5 06:01:31 localhost OSInstaller[387]: Performing volume consistency check on 'Macintosh HD'.

Sep 5 06:01:31 localhost Unknown[371]: 2015-09-05 06:01:31.926 OS X Installer[387:8303] staging failure request 'crash on OSVolumeFsckQueueElement at 0.'

Sep 5 06:01:32 localhost OSInstaller[387]: Checking Volume

Sep 5 06:01:32 localhost OSInstaller[387]: LSExceptions [0x7f9f88c2e6c0] unloaded

Sep 5 06:01:32 localhost OSInstaller[387]: Bestandssysteem controleren

Sep 5 06:01:32 localhost OSInstaller[387]: Journaled HFS Plus-volume wordt gecontroleerd.

Sep 5 06:01:32 localhost OSInstaller[387]: Extents overflow-bestand wordt gecontroleerd.

Sep 5 06:01:32 localhost OSInstaller[387]: Catalogusbestand wordt gecontroleerd.

Sep 5 06:01:32 localhost Unknown[371]: 2015-09-05 06:01:32.964 OS X Installer[387:8303] crashing now...