Mac OS X 10.4: If FileVault "secure erase" is interrupted, data loss may occur

When you turn on FileVault protection for an account in Security preferences (in System Preferences), your entire home directory is converted into an encrypted disk image. With Mac OS X 10.4 Tiger, you can also securely erase data when FileVault protection is turned on by clicking the "Use secure erase" checkbox when the "You are now ready to turn on FileVault protection" dialog sheet appears.

If you select this option, do not interrupt the secure erase process (see below)—even if "Unmounting FileVault" appears for a long time.

Tip: It's a good idea to make a back up of important files, or even your entire home directory, before turning on FileVault.

The secure erase option means that after files are copied to the FileVault encrypted disk image, they are securely erased from your computer, like the Finder's Secure Empty Trash feature.

Important: If the secure erase process is interrupted:

• You may not be able to log in with the account that you were enabling FileVault protection for.
• All files within your Home, including things that were on your desktop, in your Documents, Pictures, Movies, and Music folders, your bookmarks, Mail messages, and your application settings, may be lost (even if you can log in with a different account afterwards).

Tip: When using this option on a portable Mac, it's a good idea to make sure the AC power adapter is connected.

The FileVault secure erase process

After you click "Turn On FileVault" with the "Use secure erase" option enabled, you will be logged out and the FileVault window will appear (it looks like the Login window). A status message tells you how long it will take to move files to your encrypted home directory.

After that, the secure erase process starts, but you won't see a status message that indicates how long it may take (you'll see an "Unmounting FileVault" message in the status area).

Important: The "Unmounting FileVault" message remains until the secure erase is finished. Don't interrupt it!

The secure erase is great for ensuring that files are securely deleted after they're moved to your encrypted disk image, but this can take a while to complete, just like using Secure Empty Trash in the Finder, which can take a long time when you're deleting lots of data. How long it takes depends on how much information is in your home directory and how fast your Mac is. Don't force-restart your computer or interrupt the process in any other way.

I interrupted the secure erase process

You probably can't log in. If you can log in as a different user, you probably can't find your files (or a FileVault-created disk image) in your original user account.

Do you have another administrator account already set up? If so, log in as that when starting up instead of with the account that was interrupted during the FileVault activation. Then, use Account preferences to delete the account which you can no longer log in as. Create the account again afterwards. Finally, log in as the new replacement account. If you have a back up of important files as mentioned above, restore your important data from it. Afterwards, you can enable FileVault for the account again.

If you have no other account set up, you'll need your Mac OS X 10.4 Tiger Install disc. Start up from the disc and perform an Archive and Install installation. Do not preserve user accounts and network settings. See this document for more information.

This document will be updated as more information becomes available.