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I am trying to install Ubuntu 16.04 alongside macOS sierra on MacBook Pro 2015 Retina model.

I have installed rEFind and made the USB stick. When I tried to boot it from the USB, I got this error: Error: 

Not Found while loading legacy loader

Please make sure that you have the latest firmware update installed
...

error when booting from usb

And one suspicion is when I made the USB stick, I followed the manual approach stated by Ubuntu Wiki. (it was using terminal and something called "dd"). After the last command, I got this:
Screenshot

Any help will be appreciated.

Sumeet Deshmukh
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Xiaofeng Fan
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1 Answers1

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Booting from USB media, particularly in BIOS/CSM/legacy mode, has always been problematic on Macs. I have several suggestions:

  • Use the right bit depth -- Your Mac is new enough that it uses a 64-bit EFI. As such, you should be trying to install a 64-bit version of Ubuntu. If you're trying to install a 32-bit version, STOP! Download the 64-bit version instead and try with it.
  • Check how you prepared the USB drive -- rEFInd is better able to boot in EFI mode than in BIOS mode (see the next point), but to do so, the USB drive must have an EFI-mode boot loader installed. Depending on how you prepared the USB drive, that EFI-mode boot loader may be missing. Thus, preparing the disk with another tool, or with different options for the tool you're using, may be necessary. See "Creating EFI-Bootable USB Drives" on this page of mine for more on this subject.
  • Boot in EFI mode -- The messages you report describe failures of booting in BIOS/CSM/legacy mode. You're more likely to be able to boot in EFI mode. rEFInd is likely to display at least two options for booting an Ubuntu installation disk, one of which boots in BIOS mode and the other of which boots in EFI mode. Try picking the EFI-mode option, which will probably be described as "Boot Fallback boot loader from {description,}" where "{description}" is some sort of disk description.
  • Use Apple's boot manager -- Instead of using rEFInd, you could try using Apple's boot manager. You can get to this by holding down the Option (or Alt) key as you start the computer. It may work better than rEFInd for booting external media, especially in BIOS mode.
  • Try a CD-R instead -- Some people have reported that optical discs work better than USB flash drives for booting the Ubuntu installer on Macs. Your 2015 Mac probably lacks an optical drive, but if you've got an external one, you could give it a try. I make no promises about its working, but it's worth a try.

I wouldn't worry too much about the unreadable nature of the USB drive in OS X. Some tools (especially dd) create USB drives that are in weird formats that OS X might not recognize, although they should work fine in Ubuntu.

Rod Smith
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  • I have used Windows Rufus to create the USB stick successfully. However, the last problem(I hope it is the last one) is when I opted "Boot EFI\BOOT\grubx64.efi from UBUNTU 16_0", and when it went to installation type, it said "This computer currently has no detected operating systems...." What should I do next? – Xiaofeng Fan Apr 22 '17 at 21:53
  • You may need to use the "Something Else" installation option, as described here, among other places. – Rod Smith Apr 24 '17 at 14:39