Monday, August 29, 2016

OSX El Capitan hangs or freezes during boot or after login acutally

I twice had the case that after upgrading and after an update, my MacBook Pro froze doring / after the login screen.

What didn't help - but what's always worth a try:
  • Deleting the NVRAM (Cmd + P + R + Pwr)
  • Booting in safe mode (shift + Pwr)
So what was the Problem? Kernel Extensions!  How to fix it?
  • Boot into recovery mode (Cmd + R+ Pwr)
  • If you have FileVault enabled, open the Disk Utilities, select your main drive (which is grayed out) and select "Unlock..." in the Menu
  • Start a terminal
  • Remount everything writeable: mount -rw /
  • Naviagte to your Kernel Extensions folder: cd /Volumes/System/Library/Extensions
  • Look for new or non-standard extensions and move them in a subdirectory called "Unsupported: mkdir Unsupported; mv Stuff.kext Unsupported/
  • The list of standard extensions can be found here: ls /Library/Extensions
  • Good candidates in my case were Logitech Drivers and or a USB to Serial driver
  • Reboot
An excellent writeup of all this can be found here:
Note however, that in this tutorial, the step of unlocking FileVault is missing, which is essential when using an encrypted harddisk.