Using an AirPort Extreme with a USB External Hard Drive as a Time Capsule

The Idea

This is a fairly simple setup, but requires a few little tricks to get everything running smoothly. I would argue that this setup is better than using a Time Capsule, as it offers a bit more flexibility.

Requirements

Any Mac running OS X 10.5.x, an AirPort Extreme and your favorite USB external hard drive. For my setup, I’m using an Intel iMac and pre-unibody MacBook, an 802.11n AirPort Extreme w/ Gigabit Ethernet and a Western Digital 500GB My Book Studio Edition.

Setup

1) Plug the external hard drive directly into a Mac and fire up Disk Utility. Re-format the drive as Mac OS Extended (Journaled). Even if your drive is formatted this way out of the box (as mine was) it may be necessary to perform this step anyway.


2) Hook the drive up to the AirPort Extreme.


3) Launch AirPort Utility and click on “Disks” at the top of the window. Click on the “File Sharing” tab.

4) Make sure “Enable file sharing” is checked. The “Secure Shared Disks” option should be set to either “With a disk password” or “With AirPort Extreme Password.” Whichever you prefer will work. I did not have good results using accounts.


5) “AirPort Disks Guest Access” should be set to Not Allowed, keeping in mind that setting to Read Only will enable anyone who connects to your Extreme to mount the sparse-bundle and retrieve files from your backup, and setting it to Read and Write will give them the ability to delete files, or worse, your entire backup. Any of these options will allow you to perform a Time Machine backup, so you can allow guest access if you want, just be aware of the risks.

Make sure “Share disks over Ethernet WAN port” is checked.


6) I recommend NOT checking “Advertise disks globally using Bonjour” but this will not affect this setup.


7) Click on Update and wait for the Extreme to restart. Close AirPort Utility.


8) Open System Preferences and go to Time Machine.


9) You should now be able to select your hard drive for Time Machine. It will show up as the name of your AirPort Extreme, NOT the name of the hard drive.

If you are able to select your drive, you’re done! If not, follow these steps:

10) Open a Finder window. You should see your AirPort Extreme in the sidebar under “Shared.” Mount the server by clicking on it. If it prompts you for a user name and password, use the user name of your current OS X account, and the password you set up in AirPort Utility.


11) Your hard drive will show up as a folder. Double click to make sure you can open the folder.

Head back to System Preferences, where you should now be able to chose your AirPort Extreme connected hard drive for Time Machine Backups.

Bonus Features

You now have a Hard Drive connected to your network. This can be used to move files between machines, or even act as a server to store files you want easily accessible by multiple machines, such as your iTunes library. You can also connect the hard drive directly to a Mac for faster data transfer when doing major backups, or a full system restore.

Caveats

This setup is NOT supported by Apple, and future software and/or firmware updates may break this functionality. As of OS X 10.5.6 and AirPort Extreme firmware v. 7.3.2, it works beautifully.

Using this networked hard drive as a file server for things such as an iTunes library is not recommended, because this leaves your iTunes library on only one hard drive, and will not be backed up in the event of a drive failure of your external hard drive.

Other Notes

I have been using this successfully since October 2008 and have yet to encounter an issue.