Your Mac will not boot after an update.

Most updates to the OS X operating system are trouble-free. However, a number of clients have recently contacted us informing us of a “blank screen and cursor” problem after they downloaded an update for OS X Sierra. Upon rebooting their iMac or MacBook they were greeted by a cursor and a blank screen. Not a sight you want to see when you just want to get some work done. The problem appears to be related to some “plist” and “Apple Upgrade” files going corrupt. Apple have not yet released a fix for this issue nor have they documented the issue in their knowledge base, but our solution is quite easy to implement.

1) Start your MacBook or iMac while holding the “Command” and “S” keys simultaneously.
2) After a minute or two you will be presented with a command line terminal screen. (This is a black screen where you can input commands)
3) Now type in the following commands in sequence.

/sbin/fsck -fy
/sbin/mount -uw /
rm -f /Library/Preferences/com.apple.loginwindow.plist
rm -f /var/db/.AppleUpgrade
reboot

Press enter after each command. After you’ve entered all commands successfully your MacBook or iMac should reboot and you should be back in business!