2012 Mac Mini only starts to internal HD

[m1maverick]

I have a base model 2012 i5 which I want to prepare for resale. It is currently running Linux and I'd like to wipe the drive clean and then reinstall Mac OS X. For some reason I am unable to start this Mac using anything but the internal disk.

I first attempted to boot from a USB drive with Linux installed (so I could wipe the drive) by holding down the option key. Nothing displayed on the screen for approximately 20 minutes at which time I decided to power cycle it. I repeated this process multiple times.

Thinking there may be an issue with the USB drive I decided to boot into Internet Recovery using Option-Command-R. Figured I'd just erase the disk using Disk Utility and then install Mountain Lion. Same behavior as when I attempted to boot with the USB drive (which was not plugged in when I tried this).

Thinking maybe something went wrong with the system I started the system normally and it booted to the OS. OK, back to steps one and two with the same results as before.

Perhaps Option-Command-P-R? Did the customary three chimes and attempted all the steps I did previously. Still the same result, nothing displayed on the screen.

The system is operational as it does chime when powered on (and that's when I press the various key combinations) and it also boots to the OS on the HD. This is puzzling to me as I have a second Mini for which I did the exact procedure outlined in my first attempt description. Everything went as expected with that system.

Am I missing something?

 

[Bigwaff]

Am I missing something?

What boot manager are you using w/ Linux? If you disconnect the internal storage, does the mini boot from USB?

 

[m1maverick]

What boot manager are you using w/ Linux? If you disconnect the internal storage, does the mini boot from USB?

It's using the standard GRUB boot loader. I didn't try disconnecting the internal drive as I didn't need to do that with its identical brother. Definitely something to give a try over the weekend.

 

[bradbomb]

macOS does not use the GRUB bootloader as standard. If that is your bootloader, you have modified the EFI partition of the main drive. You definitely should disconnect the main drive and try wiping it elsewhere if Command-R is not booting up. Your USB of Linux might not boot up, but a USB of macOS might (probably more so when the internal drive is disconnected).

If you have another Mac, you should also try creating a USB installer of macOS

Create a bootable installer for macOS - Apple Support

You can use a USB flash drive or other secondary volume as a startup disk from which to install the Mac operating system. These steps are primarily for system administrators and other experienced users.

support.apple.com

 

[m1maverick]

macOS does not use the GRUB bootloader as standard. If that is your bootloader, you have modified the EFI partition of the main drive. You definitely should disconnect the main drive and try wiping it elsewhere if Command-R is not booting up. Your USB of Linux might not boot up, but a USB of macOS might (probably more so when the internal drive is disconnected).

It appears like disconnecting the internal drive is about the only option that's left. It seems odd that its twin brother didn't have any problems. It also is puzzling is that I don't even get a screen display when I attempt to select which drive to boot (holding down the option key) or trying to start Internet Recovery (option-command-R) but it does recognize option-command-O-P.