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I would like to boot an Intel Mac from Linux on an external USB drive. Right now, I have install rEFIt and use grub on the internal hard disc to boot the external drive. That seems pretty complicated. Isn't there an easier way?

In particular one that does not involved installing anything on the internal drive?

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3 Answers

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Apple doesn't want it to be easy!!!

You can perhaps ask the rEFIt devs to make the specific process you want a bit easier, but I don't think you can get without having to install something to circumvent Apple-imposed restrictions.

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Not so sure about this Apple imposed stuff. Actually some you can boot without rEFIt or anything installed as described in the link to the Ubuntu Forums below. But this is pretty complicated and kills graphics performance. But I have not given up hope for simpler ways. :-) – ovidius Aug 27 '10 at 20:20
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Using Diskutil

  1. Download the desired .img file
  2. Open a Terminal
  3. Run diskutil list to get the current list of devices
  4. Insert your flash media
  5. Run diskutil list again and determine the device node assigned to your flash media (e.g. /dev/disk2)
  6. Run diskutil unmountDisk /dev/diskN
  7. Execute sudo dd if=/path/to/downloaded.img of=/dev/diskN bs=1m
  8. Run `diskutil eject /dev/diskN1 and remove your flash media when the command completes
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If I understand you correctly, that will only give me the opportunity to boot a LiveCD from a USB stick. Which would not appear on boot menu without rEFIt installed. That does not really answer my question. I would like to have a normal Linux install on an external harddrive and at best without install rEFIt and an internal hard disc based grub. – ovidius Aug 19 '10 at 11:16
What I described above lets you create a Bootable Live USB. After you have done all those steps, restart your computer and boot from USB. If the distro allows Live mode you can boot into that if not there will be an installer. Either way you can install it on your hard drive, like you would from an CD. – 9emE0iL18gxCqLTa Aug 19 '10 at 18:03
Maybe I am dumb, but I do not understand how this helps. I have tested this on a Macbook. You cannot boot from the so generated USB stick without rEFIt installed. The whole point of my question is that I want to install Linux on an external USB drive and boot from there. I know this solution to the problem ubuntuforums.org/showthread.php?t=869324 , but was hoping for something simpler. – ovidius Aug 19 '10 at 22:03
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All you need to do is format the usb stick in a format linux can boot from, for example ext3.

Then you copy the content of a live-cd or full distro on the USB stick. Afterwards, you need to mark the USB parition as 'ACTIVE' somehow.

Then you need to go into the BIOS of the computer and set the primary boot device to USB. Then you restart.

If all goes well, Linux boots.
If it doesn't, something was done incorrectly.
It's clearly possible, I've done it on my Dell notebook.

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Could you please at least check before you answer something? It is about Intel Macs. They have no bios and what you propose just won't work. – ovidius Aug 29 '10 at 11:35
@ovidius: Every computer has a BIOS (basic input-output system), even Apple computers. And if it doesn't work, then that means you didn't manage to mark the USB partition as 'ACTIVE' (=boot) [or your BIOS doesn't support booting from USB or has disabled it]. u start the system and be4 display comming press F2 or F3 or Esc or Delete hold any key for a second then it will show u other wise go to apple website and ask help they help u. New Apple computers use EFI , so you need to know the shortcut-key combination. – Quandary Aug 31 '10 at 10:59
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Look here: en.wikipedia.org/wiki/Extensible_Firmware_Interface . If you do not have an Intel Mac and can check that your advice is really appropriate, I'd recommend that you do not claim to know what works. – ovidius Sep 1 '10 at 6:31
Yes, EFI, Extensible_Firmware_Interface, as I said. No I don't need an Intel Mac, the principle is the same on any computer. It won't boot from USB as long as you don't tell your computer to boot from USB, and for as long as the boot device is not marked as active and for as long as you have the wrong /dev/sdXY in the grub boot config... you need the shortcut-key to configure the boot device order. By default, your computer won't be booted from a USB paritition marked as active, and this default makes sense. – Quandary Oct 8 '10 at 23:53

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