I have an old Mac Mini on which I installed Ubuntu to be used as a test server. I completely formatted the hard disk before installing ubuntu, installation went fine and everything is working; so far so good.

The problem is that when I access the machine via ssh, and do a reboot, it doesn't reboot.

I get the message "going to reboot NOW" then I get a black screen as if its rebooting but then nothing happens. The machine is still running, but it is as if no restart signal has been sent to the bios.

Any ideas?


So I found the problem. The machine simply won't start without a monitor attached to it. A keyboard is not necessary, but a monitor is a must.

I tried looking around how to access the bios in mac-mini and it looks like mac has no bios but instead has Apple Open Firmware, which can be accessed by pressing Cmd + O + A. I have a standard Windows keyboard so I tried pressing windows logo key + o + a but it doesn´t seem to work

So now I'm trying to find out how to start a Mac Mini without a monitor attached to it.

**Edit 2: SOLUTION ** Answering my own forgotten question a couple of years later, but here goes You need to convince mac that it is attached to a monitor, this can be achieved by using a resistor on two holes in the VGA port, like 220Ω resistor. VGA voltage levels are 0.7V Check out this solution If by the time of reading this solution the attached link is down, then google for this "headless VGA headless vga mac" If by the time of reading this solution there is no google anymore, then I'm dead anyway and I don't care

  • Answering this might require more Linux knowhow than you will find on AskDifferent
    – nohillside
    Oct 23, 2012 at 13:32
  • please read my update. the problems seems to be mac hardware related Oct 23, 2012 at 13:47
  • I am unsure why Linux knowledge would have to do with this, and seems like a very valid question on how to boot a Mac headless.
    – jmlumpkin
    Oct 23, 2012 at 22:25
  • I did not know this machine had a BIOS. Shouldn't this be an EFI? And if your on EFI, install rEFIt to boot however you like. Oct 17, 2014 at 9:40
  • 1
    Possible duplicate of Remote into Mac Mini after a reboot
    – Allan
    Feb 21, 2019 at 23:00

3 Answers 3


Older Mac Minis don't like running headless (without a monitor)

Here's one solution involving some cunning use of a display adaptor and a 100 Ohm resistor.


You don't need a DVI to VGA adapter. Just plug the resistor between C2 and C5 holes on the DVI. (Any of C1, C2 or C3 should work, but I tried C2 and C5 first and it worked for me so I stopped right there.)

enter image description here

The resistor should be about 80 Ohm, but the closest I had was 150 Ohm resistors and that worked fine. 200 or even higher probably works too.


I was able to fix headless boot on Mac Mini 2,1 (mid-2007) by putting 80 Ohms directly between DVI port pins C2 and 15 (GND). Also tested the DVI port signal and it seems no harm was done ;)

Squeezing the resistor leg to pin C5 did not make a reliable electrical connection in my case.

My headless boot problem strangely started after switching from OS X to Ubuntu.

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