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How to Format a Bootable USB Drive on Mac after using it to install Linux

Published by

F. Jeremy Bolanos

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If you’ve created a bootable USB drive using BalenaEtcher to install Linux on an old laptop or computer, you might find the macOS Disk Utility fails when you try to reformat it for regular storage use. This issue happens because the Linux installer creates multiple partitions that Disk Utility struggles to erase properly. In this guide, we’ll walk you through how to format your USB drive on Mac using Terminal.

Why Disk Utility Fails to Format a Bootable USB Drive

When you create a bootable Linux USB drive, it often includes multiple partitions, such as EFI and EXT4, which macOS Disk Utility may not recognize or be able to remove properly. The solution? Using macOS Terminal to manually erase and reformat the USB drive.

How to Erase and Format a Bootable USB Drive on Mac

Follow these simple steps to restore your USB drive to its original storage functionality:

Step 1: Insert the USB Drive and Open Terminal

  1. Plug the USB thumb drive into your Mac.
  2. Open Terminal (you can find it in Applications > Utilities or search for it in Spotlight with Cmd + Space).

Step 2: Identify Your USB Drive

To locate your USB drive, type the following command and press Enter:

diskutil list

Look for a disk that matches your USB drive’s size. It will likely be named something like /dev/disk2 or /dev/disk3. Make sure you identify the correct disk to avoid erasing the wrong one.

Step 3: Unmount the USB Drive

Replace the diskX with the correct disk number from the previous step:

diskutil unmountDisk /dev/diskX

Step 4: Erase and Format the USB Drive

Now, use this command to erase and format the drive as ExFat (compatible with macOS, Windows, and Linux):

sudo diskutil eraseDisk ExFat "USB_DRIVE" MBRFormat /dev/diskX
  • Replace “USB_DRIVE” with the name you want for your USB drive.
  • If you prefer MacOS Extended (Journaled) format, replace ExFat with JHFS+.
  • The MBRFormat option ensures better compatibility with most operating systems.

Step 5: Verify the Formatting

Once the process is complete, check if the USB drive is properly formatted by running:

diskutil list

Your USB drive should now be listed as a single partition with the format you chose.

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