I've noticed that under 10.5.2 Time Machine now backs up my mounted FileVault volume while I'm logged in, but alas it is unencrypted this way. At least before it was only copying the encrypted sparsebundle as a whole. This underscored the need to create an encrypted backup system since I have sensitive work data that is just unacceptable to leave in the clear. I figured out how to get Time Machine to make an encrypted backup, here's how:
This worked for me, I hope it works for you too!
- Set up Time Machine to backup to an AFP volume, I haven't figured out how to make it work on a local drive.
- Let Time Machine start backing up, and then stop the backup. This should create a <machine_name>_<random_number>.sparseimage volume on the AFP drive.
- Turn off Time Machine.
- Rename the <machine_name>_<random_number>.sparseimage to old_<machine_name>_<random_number>.sparseimage.
- Open Terminal, cd to your AFP volume and encrypt the image with this command: hdiutil convert -format UDSB -o <machine_name>_<random_number>.sparseimage -encryption AES-256 old_<machine_name>_<random_number>.sparseimage
- When that's done, double click on the newly encrypted image, enter your password and check the remember my password box. After it mounts, eject the volume (this may take a little while).
- Open up Keychain Access, and locate the <machine_name>_<random_number>.sparseimage entry in your login keychain. Right click it and choose copy.
- Unlock the system keychain (requires an administrator login), right click in the right hand side and choose paste. (It will not work if the password isn't in the system keychain.) Don't forget to relock the system keychain.
- Turn Time Machine back on, and tell it to backup now.
- At this point it should start backing up successfully. Once it does, you can delete the old_<machine_name>_<random_number>.sparseimage file.
This worked for me, I hope it works for you too!