Upgrade to Yosemite from mountain lion hangs at reboot
I'm upgrading two computers, a MBP and an iMac, both Core i5 and 500GB HD, both running Mac OS X 10.8.5. I started out by creating a good full low-level backup of the MBP, so I can go back. Such a backup takes 10 hours or so and so does the restore.
After creating the backup, I downloaded and started the upgrade. Downloading and installing already was slow (it said 20 minutes, it was more than an hour before it rebooted). Now, it has been stuck at 50% of the reboot (I'm not sure if this is a first or second reboot, I might have missed one). I can't go to a log window, I'm in the light grey reboot screen with the grey Apple logo and the dark grey progress bar, which has been stuck at 50% for 2 hours now. The system has 200GB free on a 500GB HD. If I press the caps lock, the little green led turns on and off, but I might have to press the caps lock screen twice before it turns on the first time. I suspect that means that the kernel still functions.
I am doing this for my handicapped brother and he lives 350km (200mi) away and I have reserved a three days for this. I thus cannot take endless time (like waiting for a week for it to finish) and the result must be absolutely reliable because it is difficult to help him at that distance). I need a solution today, or I must go back to the old install and try again in the fall.
Basically, I wonder if there is a way to force this to complete and if I then have a situation that is reliable. If not, I need to move back to 10.8.5 and in that case I cannot put him on 1Password (because that requires Yosemite) and that was one of the reasons for the update in the first place...
I have been wondering about the possibility to do a hard reboot, do a clean install and then migrate applications and data over from the backup. But is that feasible? How do I know what parts of the applications where on the backup of the boot drive need to come over? User home directories is easy. But what about installs for multiple users (system-wide)?
Can someone (and Apple, why did you create this hopeless situation in the first place) tell me if I have a reliable way to get out of this situation?
