I can’t restart my mini!
I have a Late 2012 Mac mini which I use as a file server, running the latest version of Yosemite. Whenever it needs to be restarted, either manually or due to a software update, it proceeds normally to the startup chime, and then I just get a grey screen. Waiting for a few hours made no difference.
I added an SSD as an external boot disk, which afforded me the opportunity to reinstall OS X. However, after once completing a ‘normal restart’, the problem returned. The only workaround I have is to hold the power button to force a shutdown when I have the grey screen and then power up again. Could this be a hardware problem? James Hale Probably not, but there’s an easy way to check. Do a forced shut down and restart with D held down. This will boot into the hardware diagnostic mode to run some basic tests on your RAM, disk and motherboard. If that comes up clean, try booting in Safe Mode by holding ß. If this boots, it indicates to you that the fault is in some driver or kernel extension. You can find out which one by booting yet again, but this time in Verbose mode by holding ç+v. This will dump a message on the screen for each step in the boot process, and the last one you see before it locks up is the one responsible for the trouble. Hopefully you can use this information to roll back an update or uninstall something to get your Mac mini back on track.