Disk Utility Erase Controls on Your MacBook - dummies

Disk Utility Erase Controls on Your MacBook

By Mark L. Chambers

On your MacBook, you need to erase a disk or volume only when you want to completely wipe the contents of that existing disk or volume. You can also erase a rewritable CD (CD-RW) or DVD (DVD-RW, DVD+RW, or DVD-RAM) from this pane.


  • Erasing an entire disk deletes all volumes on the disk and creates a single new, empty volume.

  • Erasing a volume wipes only the contents of that specific volume, leaving all other volumes on the physical disk untouched.

To erase, follow these steps:

  1. Click the disk or volume icon that you want to erase from the list on the left side of the screen.

  2. Click the Erase tab.

  3. Click the format that you want to use from the Format pop-up menu.

    Always choose Mac OS Extended (Journaled) entry from the Format list unless you have a specific reason to use the MS-DOS File System (for compatibility with PCs running Windows) or the ExFAT File System (for compatibility with high-capacity USB flash drives).

    In some cases, Disk Utility will force you to choose the Mac OS Extended entry instead, but the end result is the same. Note that you do not need to format a disk or volume with the MS-DOS File System just to read a file from a PC system — Mac OS X recognizes MS-DOS removable media (such as a USB drive formatted under Windows) without a problem.

    You can also choose to encrypt a volume when formatting it — not a necessity (in most cases) for a personal Mac, but often a requirement in business and government offices.

  4. In the Name field, type the name for the volume.

    If you’re erasing an existing volume, the default is the existing name.

  5. If you’re worried about security, click Security Options and specify the Secure Erase method you want to use.

    By default, this is set to Fastest, so Disk Utility doesn’t actually overwrite any data while formatting; instead, it simply trashes the existing directory, rendering that data unreachable. Or is it?

    With some third-party disk utilities, some unscrupulous bum could actually recover your files after a simple Fast format, so you can specify alternative, more secure methods of erasing a disk or volume. Unfortunately, these more secure erasure methods can take a horrendous amount of time.

    Therefore, it’s okay to use the Fast option unless you want to make sure that nothing can be recovered, or use the Zero Out Data to take a more secure route with the least amount of extra waiting.

    For example, you’d want to use the next-slowest option (which writes a single pass of all zeros over the entire disk) if you’re selling your MacBook on eBay and you’re formatting the drive for the new owner. If you’re really set on the tightest, government-quality security, select Most Secure . . . but make sure you have plenty of time to spare!

    You can even click Erase Free Space to wipe the supposedly “clean” areas of your drive before you format. Man, talk about airtight security! Again, the Zero Out method is the fastest.

  6. Click the Erase button.

    In the sheet that appears, click Erase to confirm that you do actually want to do the deleterious deed.