Woman's hand plugging a USB drive into a Macbook
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Installing Linux on your old Mac is an easy way to give it a new lease of life. Pick a lightweight Linux distribution for best results and claw back some of the performance lost to hefty macOS updates.

Booting on Apple Silicon

Unfortunately, as of this writing in July 2021, this technique won’t work on new Apple Silicon Macs with the M1 system-on-chip or later. Corellium has already managed to port Linux to run natively on an M1 chip, but the process is much more complicated than simply writing a disk image file to a USB stick.

Linux kernel version 5.13 includes support for the new ARM-based chips, so hopefully support for mainstream distros like Ubuntu isn’t too far off. Before you start, make sure you’re using an Intel-based Mac. You can figure out which type of Mac you have using the Apple > About This Mac menu.

RELATED: How to Check if Your Mac Is Using an Intel or Apple Silicon Processor

Creating Bootable Linux USB Drives in macOS

Format Your Drive

For best results, it’s a good idea to format your USB drive to FAT before starting. Different Linux distributions have different space requirements, but around 4GB should be enough for most distributions.

Disk Utility in macOS

Launch Disk Utility (search for it with Spotlight, or find it in the Applications > Utilities folder), then click on your USB drive. If you’re satisfied you can erase the drive without losing data, click on “Erase” and then choose “MS-DOS (FAT)” as the format and give it a name. Click Erase and wait for the process to complete.

Convert Your ISO

With your Linux ISO downloaded, it’s time to convert it to the IMG format so that it can be written as a mountable disk image. Open Terminal and enter the following command:

hdiutil convert /path/to/downloaded.iso -format UDRW -o /path/to/image
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Replace /path/to/downloaded.iso with the location of your downloaded Linux ISO, for example if ubuntu.iso is in your Downloads folder, you can type ~/Downloads/ubuntu.iso.

Similarly, you’ll need to provide a destination in which the DMG will be placed (no need to add the “.dmg” extension). For ease, we’d recommend using the same location for both. Following on from the example above, you could type ~/Downloads/ubuntu.

Convert ISO to IMG with hdiutil command

Write to USB

With your IMG file ready to go, it’s time to write to USB. Head back to Terminal and type the following to get a list of drives:

diskutil list

You’re looking for the identifier for the USB drive you just formatted. If you gave it a name like “LINUX” then you should be able to spot it under the “NAME” column. The size of the disk (for example, 8GB) may give it away too.

Disk Utility listing drives

Now that you know your identifier, you need to unmount that particular drive so that you can write your DMG file to it. To do this, use the following command replacing diskX with the identifier (for example, disk3 in the screenshot above).

diskutil unmountDisk /dev/diskX
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Finally, it’s time to write your DMG file to your USB drive. You can do this with the following command:

sudo dd if=/path/to/image.dmg of=/dev/diskX bs=1m

You’ll need to replace /path/to/image.dmg with the path to the DMG file created above, and /dev/diskX with the disk identifier used above (for example, disk3). You will be prompted for your administrator password. Type it, then hit Enter to begin the copy. You may also be asked to grant Terminal permission to access a removable volume, which you should grant.

Wait for your Mac to write the contents of the DMG to your drive. This could take a while depending on the size of the DMG and the speed of your Mac or USB drive. If you see a “The disk you inserted was not readable by this computer” error, click “Ignore” and carry on.

A Disk Not Readable error message after creating a bootable drive.

Boot Linux on Your Intel Mac

Power down your Intel Mac, then insert your USB drive if you haven’t already done so. Press and hold the “Option” button then press and release the power button to start your Mac.

Keep your finger held down on the “Option” button until you see a list of devices appear on-screen. You should see your boot drive, likely labeled “Macintosh HD” and a separate USB drive titled something like “EFI Boot” with a different icon.

Click on your USB drive, then click on the upward-pointing arrow to start Linux. Your Mac will now boot from USB. If you decide to install Linux, consider a dual-boot arrangement for your Mac.

Hate Terminal? Use balenaEtcher Instead

While the Terminal provides a method of doing this that doesn’t rely on additional software, text-based commands aren’t for everyone. If you’d rather use an app to do this instead, try balenaEtcher.

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This open-source app handles the whole process for you, from converting your image to safely copying it to an external volume.

Have a Windows PC you want to boot Linux on as well? See our instructions on how to create a bootable Linux drive in Windows.

Tim Brookes Tim Brookes
Tim Brookes is a technology writer with more than a decade of experience. He's invested in the Apple ecosystem, with experience covering Macs, iPhones, and iPads for publications like Zapier and MakeUseOf.
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