With the release of Mac OS X Yosemite 10.10.3, a number of third party kernel extensions have been causing some users to experience issues during the installation of the upgrade.
These kernel extensions can cause the upgrade to fail and prevent the Mac from subsequently booting normally.
When this happens, at least in our experience, the Mac update will fail and the system will reboot. From here you may be able to get to the login screen but an attempt to login will result in failure with text showing in the top left of the screen which describes a 'kernel_panic'. I would recommend taking a photo of the screen when this information is displayed as it will provide a clue as to which kernel extension has caused the issue. Once you have followed the guide below to enable Safe Boot you can use this information to narrow down and remove the the problem extension.
Important! : If your data is critical we recommend against trying anything before backing up your files. If you cannot do this or need assistance trc can help you to retrieve your lost Mac data.
The normal process to get around this would be to start the Mac in Safe Boot. To do this you would normally:
You should now be at a login screen with Safe Boot in red letters printed at the top right of your screen next to the time.
Our experience when trying to resolve this issue for an emergency data recovery client was the following:
To be able to resolve the issue directly on the machine, Safe Boot is a must. So how did we do it?
First of all we need to boot the Mac into the Recovery Partition. The recovery partition is used by the system to repair issues or reinstall the operating system.
To access the recovery partition you must hold down Cmd ⌘ and the R key after you power on your Mac.
Once the recovery system has loaded you will be presented with the screen that you can see below:
What we need to do here is to launch the Terminal and issue a command to the system which will cause it to boot in Safe Boot mode without any special key presses at startup.
Once launched type the command below, exactly as it appears and press enter:
from here you can quit the Terminal and shut down your Mac. Now when you restart you should see the red Safe Boot message at the login screen.
Don't worry, the failed installation is completing now, this is a good thing and you should not worry about it however, it will take a little time for this process to complete.
This is where you will need the photo that was taken of your login screen. This should identify the cause of the kernel extension that is causing the system a problem. Often it is only necessary to uninstall the application (drag it to the trash and empty it), ocassionally you will need to go deeper into the system to find the problem.
It is also possible that you may not be able to identify the problem at all. If this is the case, booting in this manner will at least allow you to back up your files before reinstalling Mac OS X.
Once your problems have been resolved, you can reverse the safe boot settings by entering into the Terminal the following command:
sudo nvram boot-args="-x"
You will then be asked to enter your password.
Once you restart, you should no longer see the Safe Boot message at the login screen and your Mac should be up to date and ready to go.Access your free download
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