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What's the best way to install Ubuntu without putting GRUB on the MBR? I would think I can install to another partition (logical?), and then install GRUB on a bootable USB. When I want to boot to Ubuntu, just plug in the USB.

Would this work? How can I get the installer to do that?

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3 Answers

Why don't you want to install GRUB on the MBR? If you're installing it beside another operating system, GRUB will pick it up and still give you the option to boot into that other operating system. Alternatively, you can choose to not install GRUB at all, and let the other bootloader handle things, though this may take some configuration in the other OS. The easiest and most common thing to do in a dual-boot situation is to just let the new bootloader nuke the old one and replace it.

That said, what you want to do probably won't work, anyway. If you could do what you wanted, then you'd end up with two bootloaders trying to fight for control. That's part of why there's a Master Boot Record (MBR) to begin with.

If you want to install Ubuntu, without wiping out your other OS, that's entirely doable in a number of different ways:

  1. Repartition the drive the other OS is on.
  2. Install on a different internal drive.
  3. Install to a USB flash drive and use the "Boot to USB" option in your boot options at POST time to boot to it the same way you'd boot to a CD.
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Why don't you want to install GRUB on the MBR? Because I've been burned by this before. Granted it was an older version of Ubuntu, and a much older version of Windows - but I've had to spend hours trying to repair the MBR b/c Win wouldn't boot - it can be really finicky with stuff like this. –  Bob Nov 30 '12 at 21:52
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Grub replaces the MBR, as you know, however there should be no problems booting either Windows or Ubuntu from Grub. There are sometimes problems where the OS proper does not find the Windows boot partition however this can normally be fixed by running 'sudo update-grub' afterwards. –  fabricator4 Dec 1 '12 at 7:59
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I've never tried, but I think it would work indeed.

As for the safest way of doing this, I'd say you need to create a partition (with partition magic or any other program) for ubuntu, by shrinking the windows one.

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To do this you will need to set up the partitions for Ubuntu manually. I suggest you do this with Gparted after selecting "try Ubuntu". You should then go ahead and install Ubuntu but when Ubiquity asks how you want to install select "something else" and it will take you to the advanced mode.

You then need to specify the partitions manually, and also tell it where to install grub. Down the bottom of the advanced partitioner, you will it has probably defaulted to installing grub on /dev/sda. Change this to the correct device name for the USB you want to install grub to.

After installation the machine will only boot into Ubuntu when you boot grub off the USB drive; the MBR on the hard drive will not be changed.

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This is exactly what I want to do. I will try it. I didn't know that ubiquity lets you choose the place to install grub. Perhaps I've missed it in the past. Thanks! –  Bob Nov 30 '12 at 21:49
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