MacOS Sierra is the latest release of OS X for Mac computers. Beta version was released following the WWDC conference this year. If El Capitan release during Sept 2015 is any indicator, some of us might have run into issues with Macbook not starting up after the update.
We at AppleToolbox have seen these issues with almost every major OS X release. Majority of the problems are usually related to third party software running on your Macbook. If your Macbook will not startup at all after macOS Sierra update and hangs on a grey screen with an Apple Logo, here are some steps for you to consider:
Please try each of the Steps below till your problem is resolved:
- Press and hold the power button for a few seconds until your computer turns off, then release the power button. Wait a few seconds and then press the power button to turn on your computer.
- You can also give our detailed Mac White Screen article a try which shows all the usual steps that are taken when encountering this issue.
- Try to start Your Mac using Safe Mode. To do this, turn on your Mac, when you hear the start up sound, press and hold the Shift key until you see the Apple logo. If your Mac can start up, the problem may be that your computer do not have enough space. Did you see any low disk space warnings before this problem? Your Mac should have at least 10 GB of free space.
- Try resetting the NVRAM. You can follow Apple’s steps to reset NVRAM.
Un-Assigned Kernel Misfiring
If None of the above steps helped your issue, chances are that you have an unsigned kernel extension that is mis-firing.
Kernel Extension is a piece of code that extends the capability of the base kernel of an operating system. The kernel typically manages I/O requests, and in OS X, the file ends in “.kext.” In the past, kernel extensions that conflicted with the kernel code could cause a kernel panic—a fatal halt in the OS requiring a reboot. Using the kextstat command line utility, you can actually find out which kernel extensions have been loaded by OS X at bootup.
Starting with Yosemite, kernel extensions must be code signed by the developer with Apple authorization or OS X won’t load them. Sometimes these un-signed kernel extensions cause this headache after an OS X update.
In order to tackle the Kernel extension issue, first shutdown the Mac and turn it on while pressing and holding Cmd +R to enter Recovery Mode. Open your Disk Utility. If your drive is encrypted you will have to unlock it and enter your encryption password. Quit Disk utility and open terminal.
- Open Terminal in /Applications/Utilities
- Enter “kextstat -l | grep -v com.apple > NonAppleKext.txt” without the quotes. This will create the list of all non-Apple file extensions that you can look through to see if there is an obvious suspect. In any case, continue the steps below to remove the non-signed extensions.
- Enter “system_profiler SPExtensionsDataType > ~/Desktop/kextList.txt” without the quotes and hit return(this will take a while to run).
- There should now be a kextList.txt file on your desktop, open it and press both the “Apple(Command)” and “F” keys to bring up the find.
- In the find field insert “Obtained from: Not Signed” Copy the destination to the .kext file to a list for use later. (Click next to cycle through all of them.) Example: /System/Library/Extensions/JMicronATA.kext
- Browse your drive to /System/Library/Extensions and remove any of the unsigned kext files.
- You can also unload these kernel extensions by using the following command on your terminal window. “sudo kextunload -b com.apple.driver.ExampleBundle” Use the extension name instead of the examplebundle
Once all the unsigned extensions have been handled, Restart the Mac and you should be all set to go.
Please let us know in the comments below if you have any issues. Good luck!