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Past Episodes

How to Make an Encrypted Sparse Disk Image

In episode #195 of the NosillaCast Podcast over at http://podfeet.com Bart suggested I create my offsite backup by keeping a backup drive to work, and bringing in my laptop once a week and doing it there. Then he further suggested that I make an encrypted sparse image to back up to so no one but me could ever open it. These instructions show exactly how to do that.

Plug in the External Drive

You can see my external drive on the Desktop called The External Dart

Launch Disk Utility

Navigate to Applications –> Utilities and launch Disk Utility. When it comes up, click on New Image.

Set up the Disk Image

1) Choose your external hard drive
2) Name the disk image – this is the file name you’ll see on your hard drive
3) Name the volume – when you open the image, a new "disk" will show in the finder with this name
4) Choose your volume size. The sparse image will only be as big as the sum of what you put in it, so use the pulldown to select the size of your external drive
5) Leave the format at Mac OS Extended (Journaled)
6) Choose 128-bit AES Encryption unless you’re the CIA in which case you want 256-bit
7) Leave the default to single partition – Apple Partition Map
8) Set the Image Format to sparse disk image
9) Click Create

Enter a Password

You need to give the encryption a password and as always make it complicated so you can’t possibly remember what it is. If you remember the password in your keychain, that will make it very easy to open this image for your weekly backups but it will also make you lazy and help you forget the password, and remember that the only time you’ll need this image at all is if your laptop hard drive dies or your house goes up in smoke burning it up – so you will not be able to get to the keychain if you forget it! I would suggest not remembering it in the keychain for that very reason.

Mount Your Image

Looking at your external drive in the sidebar, you should see the image name followed by .sparseimage. Double click the sparse image.

Enter Your Password

You’ll now be prompted for that super secret really hard password you entered earlier. Resist the temptation to tell it to remember password in your keychain! I promise you’ll be glad you took my advice. Just click OK and move along.

Verify Your Image

You’ll now see your volume in the left sidebar and it will act just like a regular drive. When you’re all done, eject the volume, then eject the hard drive and throw it in a drawer till next week’s backup!