Frequently Asked Questions about encrypting the backup volume

This documentation is for an older version of CCC. You can find the latest version here.
Last updated on March 15, 2017

Can I back up an encrypted volume to a non-encrypted volume?


If I back up an encrypted volume to a non-encrypted volume, will the copied files be encrypted on the destination?

No, encryption occurs at a much lower level than copying files. When an application reads a file from the encrypted source volume, macOS decrypts the file on-the-fly, so the application only ever has access to the decrypted contents of the file. Whether your backed-up files are encrypted on the destination depends on whether encryption is enabled on the destination volume. If you want the contents of your backup volume to be encrypted, follow the procedure documented here to enable encryption.

Will Carbon Copy Cloner enable encryption on my backup volume?

No. You can enable encryption in the Security & Privacy preference pane while booted from your bootable backup, or in the Finder by right-clicking on your backup volume.

Do I have to wait for encryption to complete before rebooting from my production volume?

No. Once you have enabled encryption on the backup volume, you can reboot from your production startup disk and the encryption process will continue in the background.

What happens if I change my account password on the source volume? Does the encryption password on the backup volume get updated automatically?

The encryption password(s) on the backup volume will not be automatically updated when you change the password for an account on the source volume. When you boot from the backup volume, you may notice that your user account icon is a generic icon, and the text indicates "[Update needed]". The update that is required is within the proprietary encryption key bundle that macOS maintains for your encrypted volume. This encryption key is not maintained on the backup volume, and it is Apple-proprietary, so it isn't something that CCC can or should modify. To update the encryption password on the destination volume:

  1. Choose the backup volume as the startup disk in the Startup Disk preference pane and restart your computer. You will be required to provide the old password to unlock the volume on startup.
  2. Open the Users & Groups preference pane in the System preferences application.
  3. Click on the user whose password was reset on the source volume and reset that user's password again. Resetting the password while booted from the backup volume will update the encryption key for that user on the backup volume.
  4. Reset the password for any other user accounts whose password was reset on the original source.

I enabled encryption on my 3TB USB backup disk. Why can't I boot from that volume any more?

Some versions of OS X have difficulty recognizing USB devices that have been encrypted with FileVault. The Western Digital My Passport Ultra 3TB disk, for example, works fine as a bootable device when not encrypted. In our tests, however, this device was no longer recognizable when FileVault encryption was enabled. This problem appears to be limited to OS X 10.11 El Capitan. The same volume was accessible using older and newer OSes, and also functioned fine as an encrypted startup device using older and newer OSes.

I formatted my destination as encrypted, and it's bootable. Why do you recommend cloning to a non-encrypted volume first?

We generally recommend that people establish a bootable backup on a non-encrypted volume, and then enable FileVault while booted from the destination. Some people have discovered, however, that a pre-encrypted volume can (will usually) function as a bootable device. So why do we recommend the former? There are a couple notable differences between pre-encrypting the disk vs. enabling FileVault after booting from the not-encrypted disk. When you enable FileVault via the Security Preference Pane:

  • You get a sanity check that a recovery volume exists (this avoids spending lots of time copying files only to find out that the volume might not be bootable)
  • You get the opportunity to store a recovery key with Apple
  • You can unlock the disk with selected accounts
  • You get a nicer UI on startup to unlock the disk (e.g. it's similar to the LoginWindow interface), vs. a less-polished looking Unlock Disk interface

One drawback to enabling FileVault via the Security Preference Pane, however, is that changes to account passwords on the source volume aren't immediately reflected on the backup as far as unlocking the disk is concerned. The old account passwords would be required until you boot from the backup and specifically re-enable those accounts in the Security Preference Pane (at which time the disk's EncryptionKey is remastered).

As far as the backups are concerned, there's no difference between these two methods. There is still an order-of-operations concern with pre-encrypting the disk. You'd want to approach it in this manner:

  1. Erase the destination device (unencrypted!)
  2. Click on the freshly-erased disk in CCC's sidebar and create a recovery volume on that disk
  3. Go back to Disk Utility and erase the volume now, not the whole disk (as was emphasized in the instructions above). Now you can choose the option to encrypt the volume. By erasing just the volume here, not the whole disk, the hidden recovery partition that CCC created won't be destroyed.
  4. Open CCC and configure your backup task

In general, either procedure is fine, it really is the same as far as the backup is concerned. We generally prefer the Security Preference Pane method, however, because it yields the same UI behavior you are expecting if you have enabled FileVault on your production startup volume. Many people become concerned when the Disk Utility-encrypted volume shows any behavioral difference at all with regard to unlocking the disk on startup, and that concern is best avoided by enabling FileVault in the Security Preference Pane.