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.
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
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.
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.
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
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.
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.