I have a couple of Apple Power Mac G5 machines that I have deployed as servers: they're running GNU+Linux, connected to the world only via an ethernet cable.

When I need to restart these machines, they will hang at some early stage; eventually the fans will switch to full-speed and the noise will draw someone's attention and they will call on me. I then connect a monitor and keyboard, restart the machine, and it boots fine. Further diagnosis shows that the machine will not boot properly unless a keyboard and monitor are connected.

This has nothing to do with MacOS, since it's not on the machine any more. It also has nothing to do with GNU+Linux, since it hangs very early, before the point where the OS is involved. Is it a BIOS setting? (Update 2009-11-29: morgant's answer suggests that it could be a failure in the boot loader; I'll investigate this.)

How can I change it to boot correctly without monitor or keyboard?

  • As mentioned in Sven's answer, there appears to be no way to change this short of modifying the hardware. – bignose Apr 20 '11 at 5:32

As far as I know, they will fail when trying to boot up without a monitor connected, and there is no way to change that, in OpenFirmware or otherwise. The keyboard should be irrelevant.

Here is a post that describes a way to solder yourself a device that tricks the GPU into detecting a non-present monitor.

Another idea I never tried would be to see if it boots up when there is no gpu at all installed.

  • Thanks. I wasn't looking for making changes to the hardware (so can't evaluate whether they work in this case) but I appreciate the suggestions. – bignose May 7 '11 at 1:07
  • 1
    @bignose: just soldered myself one of these according to the linked recipe and it works perfectly fine. The PowerMac G5 now boots up headless and will happily show the screen contents if you connect a screen later on. – 0xC0000022L Jan 20 '12 at 19:19

I have many G4, G5, and Intel Xserves, plus PowerMac G4s & G5s an Mac Pros that are run completely headless and boot and operate sans keyboard and/or monitor without issue, but they're all running Mac OS X or Mac OS X Server. I have a couple PCs and a couple Intel Macs running various Linux installs (unfortunately I don't recall which boot loader my coworker used, off the top of my head) and some of them do have issues booting without keyboards attached (monitors haven't usually seemed to make a difference, but one is an iMac). So, my guess would be that the issue is with either the EFI boot loader you're using or with the distro & version of Linux.

  • 1
    From the timing, I know that the difference in behaviour becomes evident too early for the operating system to be a factor. But I'd neglected that there is also a different boot loader; that bears further investigation. Thank you. – bignose Nov 28 '09 at 13:46
  • I have this problem with an 2013 Mac Pro. I restart it remotely, and it never boots up (until I connect a KB and monitor to it). – Stan Jun 28 at 14:18

The accepted answer is wrong.

The behaviour you see has nothing to do with Open Firmware and everything to do with yaboot. By default a small script (the "l for Linux, c for CDROM" screen) will be booted (via the tbxi attribute) before yaboot. That scripts blocks if no monitor is connected.

The solution is pretty simple, edit the OF variable boot-device to not point to <somedevice>,\\:tbxi but to <somedevice>,\\yaboot instead. This can be done from Linux with the NVRAM commands (nvsetenv) or on the OF shell with setenv.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.