Encrypted sparse bundle images

[DavidCB]

I recently used SD to copy my User folder to a sparse bundle image. Now I would like to encrypt the image, but realize that it can't be done after the fact.

If I create a new sparse bundle with Disk Utility, can I use SD to copy the first image to the second one? If so, is there a difference between copying the contents of the image as opposed to the image itself?

Thank you,

David

[dnanian]

You can, sure. You'd basically be doing the same thing as re-copying the source files.

[DavidCB]

Should I specify to back up the User files (which is what I originally copied from my hard drive) or all files?

David

[dnanian]

All files.

[DavidCB]

How do I determine what size to make the target encrypted disk image?

The source User folder is 33.37 GB but the mounted disk image itself, which was created from within SD, is 130.73 GB (96.94 GB available). If I use Get Info on the unmounted disk image, it's 34.28 GB.

Also, when backing up, should the source disk image be mounted or unmounted? What about the target disk image?

David

[dnanian]

You should make it the full capacity of the source drive, since that's the largest it could become.

You'd have to ensure the source is mounted. The destination's password needs to be in the keychain, and it should auto-mount.

[DavidCB]

Sorry to be a little confused--is there a reason the target image needs to be so much larger than the User folder itself? (It's a backup archive; I won't be adding to it later.)

David

[dnanian]

Much, no. Larger, yes - you'll need some working space.

But "empty" space in a bundle, especially if you only use it once, doesn't create a significantly larger file. It's a virtual disk.

[DavidCB]

Much, no. Larger, yes - you'll need some working space.

But "empty" space in a bundle, especially if you only use it once, doesn't create a significantly larger file. It's a virtual disk.

So, if my User folder is 35 GB, would a 50 GB disk image be large enough? The reason I am asking all this is because when I made the original backup to a disk image, SD created about a 135 GB sparse bundle for a 35 GB User folder. That made me think there might be some special reason for the much larger image.

If I were creating a hard-drive partition for such a backup, I would think 50 GB or even 40 GB would be fine?

David

P.S. On reflection, I now realize that SD may have created a 135 GB sparse bundle because the original source volume was 125 GB (with about 78 GB used).

[dnanian]

Correct. We sized the bundle based on the size of the source volume. You decide how big you want it, David: I think I've given you my thoughts...