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How To Boot Ubuntu on a Mac from External USB Storage

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In this comprehensive guide, we will walk you through the process of booting Ubuntu on a Mac from an external USB storage device. This process involves creating a bootable USB stick, partitioning your USB device, installing Ubuntu, and setting up the necessary bootloaders.

Quick Answer

To boot Ubuntu on a Mac from external USB storage, you need to create a bootable USB stick with Ubuntu, partition your USB device, install Ubuntu, and set up the necessary bootloaders. Once done, you can boot Ubuntu by holding down the Option key during startup and selecting the EFI Boot option from the boot menu.

Preparing the Bootable USB Stick

The first step is to create a bootable USB stick with Ubuntu. You can download the Ubuntu ISO file from the official Ubuntu website. Once you have the ISO file, you can use a tool like UNetbootin to create the bootable USB stick.

Partitioning the USB Device

Next, you need to partition your USB device. This involves creating an EFI boot partition, a partition for the Ubuntu /boot directory, a swap space (optional), and one or more partitions for the rest of the Ubuntu system.

Here’s an example of how you can partition your USB device:

  • 200MB EFI boot partition
  • 200MB ext2 partition, mounted to /boot
  • Swap space (optional)
  • One or more ext4 partitions for the rest of the Ubuntu system

To create these partitions, you can use a tool like GParted.

Installing Ubuntu

Once your USB device is partitioned, you can proceed with the Ubuntu installation. Boot from the USB stick and follow the prompts to install Ubuntu on the USB device.

Setting Up the Bootloaders

After installing Ubuntu, reboot to OS X. You will need to install two tools: gdisk and rEFInd.

  • Gdisk is a GPT fdisk program. You can install it using Homebrew with the command brew install gdisk.
  • rEFInd is a boot manager that will allow you to choose between OS X and Ubuntu at boot time. You can download it from the official website.

Once you have these tools installed, open the Terminal and run the command diskutil list. This will list all your connected devices. Identify your USB device and its EFI partition (e.g., /dev/disk3, /dev/disk3s1).

With the device and partition identified, you can follow the instructions provided in the gdisk recipe under “Fixing the installation” point 6.

After setting up gdisk, you can install rEFInd on the EFI partition of your USB device. Navigate to the rEFInd directory and run the command:

./refind-install --usedefault /dev/disk3s1

Replace /dev/disk3s1 with the appropriate EFI partition of your USB device. The --usedefault option tells rEFInd to install itself to the default location, and the /dev/disk3s1 parameter specifies the EFI partition.

Booting Ubuntu

Now you’re ready to boot Ubuntu from your USB device. Reboot your Mac and hold down the Option key to access the boot menu. You should see an option to boot from the EFI Boot, which will take you to rEFInd. From there, you can select to boot Ubuntu.

Congratulations! You have successfully booted Ubuntu on your Mac from an external USB storage device. If you encounter any issues, refer to the detailed guide at

Remember, this process can vary slightly depending on your specific hardware and software configurations. Always make sure to back up any important data before making changes to your system.

Can I use any USB device to boot Ubuntu on a Mac?

Yes, you can use any USB device as long as it has enough storage capacity and is compatible with your Mac. However, it is recommended to use a USB 3.0 device for better performance.

Can I use a different tool to create a bootable USB stick instead of UNetbootin?

Yes, there are other tools available to create a bootable USB stick, such as Rufus (for Windows) or Etcher (for both Windows and Mac). You can choose the tool that you are most comfortable with.

Do I need to format my USB device before partitioning it?

Yes, you will need to format your USB device before partitioning it. Most partitioning tools, like GParted, will give you the option to format the device during the partitioning process.

Can I install Ubuntu on the same partition as my existing macOS installation?

It is generally recommended to install Ubuntu on a separate partition to avoid any conflicts with your macOS installation. However, if you have enough free space on your existing macOS partition, you can create a new partition and install Ubuntu on it.

Is it possible to dual boot Ubuntu and macOS on a Mac?

Yes, it is possible to dual boot Ubuntu and macOS on a Mac. By using a boot manager like rEFInd, you can choose between Ubuntu and macOS at boot time.

Can I remove Ubuntu from my USB device after installation?

Yes, once you have successfully installed Ubuntu on your USB device, you can remove the Ubuntu ISO file and any other installation files from the USB device. However, make sure to keep the necessary bootloaders (gdisk and rEFInd) on the USB device for proper booting.

Can I use this guide to boot Ubuntu on a Mac from an internal hard drive?

No, this guide specifically focuses on booting Ubuntu from an external USB storage device. The process for booting Ubuntu from an internal hard drive on a Mac may be different and may require additional steps.

Can I use this guide to boot a different Linux distribution on a Mac?

While this guide is specifically written for booting Ubuntu on a Mac, the general steps and principles can be applied to other Linux distributions as well. However, there may be some differences in the specific tools or commands required for different distributions.

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