OS X Legacy FileVault - "There isn't enough space on your hard disk..." alert

When turning Legacy FileVault on or off in Security & Privacy preferences, you may see an alert if you are low on disk space: "There isn't enough space on your hard disk to turn on (or off) FileVault."

Create a new user account and transfer your data to the account via a sparse disk image. If you're using OS X Snow Leopard or earlier, you can then re-enable Legacy FileVault on the new account or leave it off if desired. When you're done, you can delete your original account to recover disk space.

Important: Before performing these steps, you should back up your data (or your entire home folder) as a precaution.

  1. Start up in Safe Mode.
  2. Log in to your account if you haven't already.

Create an interim disk image to transfer home folder files to
Do not open any other applications while completing these steps.

  1. Open Disk Utility from the Utilities folder in the Applications folder.
  2. From the File menu, choose New > Blank Disk Image.
  3. From the Format: pop-up menu of the Blank Disk Image window, choose "sparse".
  4. Adjust the Size pop-up menu. The disk image should have enough capacity to hold the contents of your home folder (directory). You can choose "Custom..." from the Size pop-up menu to enter a specific size if needed (if you need more than 4.7 GB, for example).

    It's OK if you make the image a little larger than you expect you'll need. For example, if you have 2.3 GB of stuff in your Home, you might create a 2.6 GB (or larger) image.
  5. Give the image a unique name, but save it somewhere outside of your Home (don't save it on the desktop or in Documents, for example). You could save it at the root level of your Mac OS X volume, or on a different partition or different disk.

    Note: If your hard disk does not have enough free space for the new image, create it on an external disk or different partition which has enough space.
     
  6. Mount the new sparse disk image.
  7. In the Finder, select the image volume and choose Get Info from the File menu. Make sure "Ignore ownership on this volume" is selected (at the bottom of the window).
  8. Open your home folder (from the Go menu, choose Home).
  9. Select all items in your Home and drag them (copy) to the mounted sparse disk image. Advanced note: Invisible files or folders might not be copied; usually this should present no issue or only a minor issue--for example, ssh users will need to accept the ssh key after completing these steps.

Create a new user account

  1. From the Apple menu, choose System Preferences.
  2. From the View menu, choose Accounts or Users & Groups.
  3. Create a new account that has the same privileges as your original, current account (enable "Allow user to administer this computer" if it is enabled for your current account). You may wish to give it a name similar to your current account.
  4. Log out of your account and log in to the new account created in the previous step.

Copy files from the disk image to your new account
Avoid opening any other applications during this process.

  1. Mount the same, new sparse disk image that you copied files to.
  2. In the Finder, select the image volume's icon and choose Get Info from the File menu.
  3. Make sure "Ignore ownership on this volume" is selected (at the bottom of the window).
  4. Highlight all items in the sparse disk image and drag them into your new account's home folder (from the Finder's Go menu, choose Home). You may be prompted to confirm that you wish to replace some items.
  5. Restart when the copy has completed.
  6. Log into the new user account and verify that all desired data has been transferred and that you can open files as expected (things on your desktop or in your Documents folder, for example).
  7. If desired, enable FileVault for this account in Security & Privacy preferences.

Reclaiming disk space

If you want to reclaim the disk space used by the old account, use System Preferences to delete the original user account. You can also delete the interim sparse image.

Important
: Do not delete these items unless you are sure that all files have been properly copied. Advanced users should make sure any needed invisible files were copied, if not you can use Terminal to copy or move them.

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