I reinstalled the operating system over the Internet. I could boot into Recovery Mode ( Cmd+R+Pwr) and used this to access Disk Utility to run First Aid (no errors were found), and then used Terminal to run resetpassword which was then used to reset permissions on my user folder. This seemed to be meaningful, but was ultimately a wild goose chase. I was unable to boot into Single User Mode ( Cmd+S+Pwr), but it and Verbose Mode ( Cmd+V+Pwr) did show that the boot process was hanging and the last message it displayed was: pci pause: SDXC I reset the SMC ( Shft+Ctrl+Opt+Pwr while off, then Pwr), I reset the PRAM ( Cmd+Opt+P+R+Pwr while booting, then hold until the chime sounds again), I tried to boot into Safe Mode ( Shft+Pwr). Thus when I was notified that it was available, I dutifully upgraded… and then my MacBook Pro Retina wouldn’t reboot. After Update, OS X Won’t RebootĪfter upgrading to OS X El Capitan (10.11) when it was released, I had been generally pleased with the new version but there were a few quirks – like random beach ball pauses – that made me think the 10.11.1 update would address some of them.

It seems to have left behind a kext named .kext and once I deleted it, things work again. Before I knew this I installed Malwarebytes to check for spyware/adware causing the CPU usage, then uninstalled it after installing the OS X beta. I am using the Beta version because 10.13.2 had very high CPU usage by the WindowServer process that was fixed in 10.13.3. Update – I updated to 10.13.3 High Sierra Beta 5 and once again was unable to boot. Removed everything older than 2016 after running ls -lat. This time I had to remove kexts from /System/Library/Extensions. Update – I updated to 10.12.6 and once again was unable to boot.

Update – This has been an issue for myself and others running OS X Sierra as well. Update – It happened again when I updated to 10.11.4! Even fewer clues this time, additional details and an updated script to remove non-default kext files at the very bottom. Otherwise feel free to read the saga below! If your OS X El Capitan/Sierra/High Sierra update won’t reboot you can skip to the fix or check here for the (mostly) automated fix script.

Mac os x sierra virtualbox