Yosemite has been playing nicely on my MacBook Air so I decided it was time to upgrade the iMac.
After doing all the usual safety procedures and testing the backups it was time to upgrade. The iMac has had a few OS X upgrades since I bought it – it came with 10.6 Snow Leopard – and I did consider doing a clean install. However the “normal” upgrade route has had good reports so I opted for that.
The upgrade proceeded smoothly to begin with and I left it to get on with it, however when I returned some time later it seemed to have stuck on the last install screen at 50% complete. I left it for about half an hour and nothing had changed so I did what any highly trained Mac technician would do.
I powered it off and on again.
That did the trick and the iMac booted happily. I had been pretty sure it had got stuck at the reboot stage of the process so turning it off and on again forced the reboot it should have done by itself. Just to be on the safe side I then restarted it up in Safe (or Single User) Mode (Cmd + S) and ran /sbin/fsck -fy. Next, I booted from the Recovery Partition (Cmd + R) and used Disk Utility to repair permissions on the iMac’s startup disk.
Since then it has been fine and I’m now in the process of reorganising my data files to take advantage of iCloud Drive.