Ext HDD is 3,5" 4TB WD RED (exFAT) in USB 2.0 box with external power supply (220v)

When I restart my Mac Mini (late 2012, MacOS 10.14) in 90% the boot will end on black screen (no apple loading logo, no progress bar). When I turn off or disconnect my ext HDD (exFAT), or reset PRAM then the system will boot perfectly. Then I can reconnect my extHDD and everything will work (till next restart).


Assuming you have not installed a third party dual boot loader such as rEFInd, go into the System Preferences and select the internal HD as the "Startup Disk." If you have installed a third party boot loader it may be damaged or you may need to uninstall. If you don't know what a third party boot loader is; you probably don't have it.

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    I don't want to boot from extHDD. I want to boot from my system HDD. So dual boot loader or Startup Disk is not relevant. – Lukas P. Feb 15 '19 at 8:47
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    @LukasP. Have you taken the steps suggested by magic in seeing that the internal drive is selected as the "Startup Disk?" – DavidSupportsMonica Mar 16 '19 at 8:11
  • The Internal HD is and has to be startup disk, because ext USB doesnt isn't bootable. So there is only one bootable drive and that is the internal one. – Lukas P. Mar 17 '19 at 13:11
  • Try starting up in Verbose mode (Command-V) (If you end up at a unix prompt type "reboot" to restart) It will print out a lot of messages to the screen. I am guessing at some point it will just stop as it looks for an OS on the external drive. Read though that to see if there are references to the external drive. (of course you can not cut and paste to here for us to try and help decipher. sorry. ) – magic Mar 18 '19 at 14:16

So problem was with extHDD on exFAT. After reformating to NTFS is everything OK.

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