How to Erase and Format a USB Drive on Mac OS X

I recently needed to format an external 5TB Seagate Backup+ Desk Media USB hard drive.So, I decided to use the Disk Utility application, which is included in Mac OS X. This post describes the how to erase and format a USB Drive on Mac OS X and also addresses a particular error scenario I encountered:

Mac OS X - Disk Utility Error - Erase process has failed. Click Done to continue.
Mac OS X Disk Utility: Erase process has failed. Click Done to continue.

Connect the External USB Hard Drive or USB Storage Device

Plug-in the USB storage device and let Mac OS X mount it automatically. As a result, the device will appear as an icon on the desktop as shown below. Here, I have connected a Seagate 5TB external USB hard drive, which I want to erase and format.

Mac OS X - External USB Drive Mount Icon on Desktop
Mac OS X: Desktop icon for mounted external USB drive

If the device can not be mounted, it may be currently formatted using a file system format that is not supported by Mac OS X or the drive can not be read for some other reason. In this case, you can continue by launching the Mac OS X Disk Utility application.

Use the Mac OS X Disk Utility Application to Erase and Format USB Device

Press F4 to open the Mac OS X Launchpad and use the search bar to find the Disk Utility application. Click on its icon to start it.

Mac OS X - Find Disk Utility Application
Mac OS X Launchpad: Find and launch Disk Utility application

In the Disk Utility application, select the hard drive that you want to erase and format. Please note that all data on that drive will be permanently deleted once you start the erase and format process.

Mac OS X Disk Utility -
Mac OS X Disk Utility: Select external USB drive to be erased and formatted

If your hard drive does not show up by its name in the left-hand side list as shown above and you select a disk instead when clicking on Erase, you may get an error as shown in the following screen shot:

Mac OS X - Disk Utility Error - Erase process has failed. Click Done to continue.
Mac OS X Disk Utility: Erase process has failed. Click Done to continue.

When clicking on Show Details, an error, saying that there is not enough space on the device, or similar, may be shown:

Mac OS X Disk Utility - Erase Process Has Failed - Show Details - MediaKit reports not enough space on device for requested operation
Mac OS X Disk Utility: Erase Process Has Failed. MediaKit reports not enough space on device for requested operation.

Use the list view icon in the upper right-hand corner of the Disk Utility application and switch the view to Show All Devices.

Mac OS X Disk Utility - Switch view to Show All Devices
Mac OS X Disk Utility: Switch view to Show All Devices in sidebar

The external USB storage device should now be listed by its name, select it and click on Erase to continue.A new dialog will appear. It allows you to enter a name for the external USB drive and to select a format. Leave the Scheme to GUID Partition Map, unless you specifically need a different one or want to make the drive bootable.

Mac OS X Disk Utility - Erase options - Enter disk name, format and scheme
Mac OS X Disk Utility: Enter new disk name, select file system format and scheme

Security Options

Click on Security Options… to change the default settings. By default, the drive will be erased using the fasted, most unsecure method. The data can be recovered quite easily using disk recovery applications. If you plan to sell this drive or need to permanently delete sensitive data, make sure to use a more secure erase method.

Mac OS X Disk Utility - Set security options for disk erase
Mac OS X Disk Utility: Set security options for disk erase

The Security Options dialog provides four options, ranging from Fastest to Most Secure:

Security Option 1 (Fastest) – This option does not securely erase the files on the disk. A disk recovery application may be able to recover the files.

Security Option 2This option writes a pass of random data, and then a single pass of zeros over the entire disk. It erases the information used to access your files and writes over the data two times.

Security Option 3 This option is a DOE-compliant 3-pass secure erase. It writes 2 passes of random data followed by a single pass of known data over the entire disk. It erases the information used to access your files and writes over the data 3 times.

Security Option 4 (Most Secure) – This option meets the US Department of Defense (DOD) 5220-22 M standard for securely erasing magnetic media. It erases the information used to access your files and writes over the data 7 times.

Erase and Format Process

Select a security option and click on OK and then on Erase to start the erase and format process. Depending on the selected security options and on the size of the storage device, the erase and format process may take a few minutes, several hours or several days.

Mac OS X Disk Utility - Erase Process - Progress of secure erase
Mac OS X Disk Utility: Progress of secure erase

In my case, where I erased a 5TB Seagate Backup+ Desk Media, the process took about 3 to 4 hours. Once the erase process is completed, the Disk Utility will show a success message. Click on Done to close the overlay.

Mac OS X Disk Utility - Erase Process is complete, click Done to continue
Mac OS X Disk Utility: Erase process is complete, click on Done to continue

The USB storage drive is now ready for use and will be automatically mounted by Mac OS X. The Disk Utility shows details about the storage device. Here, 1.31GB are used by the file system and nearly 5TB are now available.

Mac OS X Disk Utility - Showing details of external USB hard disk
Mac OS X Disk Utility: Showing details of external USB hard disk

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.