I'm on a mac on dual boot, I've got my hard drive partitioned so that it can run OS X and Windows. Now I've got an external hard drive that I want to install Ubuntu 14.04 on it and use it on my mac.

I created a live usb and ran Ubuntu and I did everything needed to install Ubuntu on my external hard drive. One of my problems was that I did everything without internet access on Ubuntu, but I solved it now.

During the installation I got an error message saying that I couldn't install the bootloader on my external hard drive. So I continued the installation in order to manually install the bootloader.

So what should I do? Where should I install the bootloader in order to run Ubuntu from my external hard drive? Should I install it on my mac partition? I want my mac to boot even when I don't have access to my external hard drive.

  • Can you elaborate on the error you got trying to install to the external HDD? – Mitch Oct 10 '14 at 18:32
  • I can't find the exact message but it said something like unable to install bootloader on /dev/sdb (the external hard drive) and then it gave me the options to try and install the bootloader on the mac partition or continue without installing the bootloader or cancel the installation. So right now my external hard drive has Ubuntu 14.04 installed but not the bootloader. – captain Oct 10 '14 at 18:42

With Macs, I think if you put the make the device bootable (e.g. treat it like the live USB) and hold the Option key while booting up, the mac EFI will recognize the bootable external HDD and give you the option to boot from it.

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  • It doesn't work because the external hard drive doesn't have a bootloader – captain Oct 10 '14 at 18:30

Booting an external USB on a Mac isn't that simple. You do want to install a bootloader to an EFI partition, but as far as I know it's not possible to get it to boot without using rEFInd.

I asked an answered a question about booting Ubuntu on external USB storage on a Mac here: How to boot Ubuntu on a mac from external USB storage? which you should see for detailed information, but in brief you need to:

  1. Create an EFI partition when installing Ubuntu
  2. Reboot to OS X and fiddle the boot sector
  3. Install rEFInd on the device
  4. Boot to rEFInd and then to the GRUB loader on the EFI partition.
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  • When you say Get gdisk (pkg installer for OS X) and rEFInd binaries do you mean installing rEFInd on my mac? Because I already have rEFInd on my mac as a bootloader. – captain Oct 19 '14 at 19:52
  • So I still got the error with the bootloader, I continued without instaling a bootloader and followed all the steps provided by the link you gave me but when I reboot I get an option to boot into rEFInd and it loads rEFInd and I get back to the same screen... – captain Oct 20 '14 at 16:47
  • I meant get gdisk and follow the instructions to use it to modify the boot block on the USB device; and in my case I just installed rEFInd on the USB device, not on my Mac. I'm unsure of what difference it makes if that's the Mac's bootloader, but would have thought it would be fine. – Coljac Oct 21 '14 at 12:54
  • Yes, I followed the instructions you posted but I can't make it boot into ubuntu. I can only boot to rEFInd from the external HDD. Did you also have the same issue when installing the bootloader while the ubuntu installation was running? – captain Oct 24 '14 at 11:16

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