Note: Apple’s latest Leopard update allows you to access external disks from the Airport extreme without the Terminal hack (step 3). Otherwise, everything else in this post still applies!

I still can’t believe their latest maneuver. Before the release of 10.5 Leopard, Apple began advertising for this great feature called “Time Machine” that was going to be a part of their new system. Then, almost by the desire of fate, along came this shiny new 802.11n spec Wireless Router called Airport Extreme. One of the main motivations for the customers who bought this new generation of Airport Extreme bases was that it would be possible, with the release of 10.5, to wirelessly backup all files and folders – yes even an entire hard disk – without cables. Then, at the last minute, this feature was yanked. That left thousands of users, me included, sitting here blinking our eyes in amazement. I had even gone so far as to purchase and partition a dedicated hard disk for my wife and I to split. Then, as time went on, we found out why this cool feature was yanked. “Apple needed more time”, “It wasn’t stable yet”, “Too difficult to implement with large files”. blah. But we understood. It was, after all, Apple and we are slavish followers of their often times questionable judgment.

In the weeks that followed, I played around with some of the hacks that appeared on Mac blogs but I didn’t dare implement them because I had heard of the risks involved. But then Apple announced the launch of Time Capsule. That’s right: a new Hard disk with the 802.11n wireless router included! 300$ will get you 500 GB of this beauty. And it’s fully Time Machine Compatible! But what about all the poor saps who paid for the Airport Extreme? Apple seems to say “meh”. It’s possible that they will add support for it later. Who knows
When I heard this news, I decided to go for the hack. I bought all these things and I was damn well going to get them to run. Here’s how I did it.

• Note: I am going to recommend that you dedicate a separate USB hard disk to this project. This method is not supported by Apple. so It is always a good idea to have an additional backup scheme for your files. Another possible option would be to create two partitions on the same disk and use one partition for the Wireless backup.

Preparation:
You are about to back up your system. It is recommended that you do the following:

1. Upgrade to the latest version of Leopard- currently 10.5.2. This version includes some interface fixes for Time Machine, and it will avoid your having to backup the data that gets added with the update later.
2. Empty your trash and get rid of bulky and extra data.
3. Unplug iPods and all other external hardware.
4. Plug your computer into a power source.
5. Disable energy saver by sliding “Put computer to sleep” to “Never”.The screen can still be set to go to sleep if you would like

How to set up a Wireless backup scheme with Apple’s Time Machine and the Airport Extreme Base

1) Reformat your USB hard disk

You will need to clear all files from your target hard disk. You can use Disk Utility for this purpose. Select the target hard disk and then “Erase”. Make sure the Volume Format pulldown list is at Mac OS Extended (Journaled). Reformatting will erase all files forever! Please only execute this step if you have a Hard Disk or partition set aside for experimentation.

2) Plug hard disk into Airport Extreme Base (AEB)

3) After disk is discovered, enter the following line into Terminal.app
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

This will enable your Macintosh to find “unsupported” disks, including the disk plugged into AEB.

4) Open up System Preferences, select Time Machine, Turn it Off

“Now that’s a strange step” you might say. But Time Machine really has no controls as it’s supposed to do everything on its own. This means that it might start kicking it before you know what’s happening, and we want things to go nice and slow here.

5) Select “Change Disk” and choose your Airport Extreme-connected disk (AirDisk).

You should be able to choose your AirDisk without any problems. If your Airport Disk doesn’t show up, wait a bit and try again. Click “Use for Backup”

6) Test backup

Go to Time Machine’s preferences and exclude everything from backup except one small folder located on the desktop or somewhere else. This will take a few seconds to organize, but it’s worth it.
Because we are now backing up to the sparse bundle, TIme Machine needs to start from the beginning, meaning it needs to back up your entire system. Things also move much slower with Wireless Time Machine than with it’s plugged-in counterpart. Therefore, it’s a good idea to test everything before you use time on making a complete backup. What I did was return to Time Machine’s options (located in System Preferences) and exclude everything from backup except one folder located on the desktop, for example.

Midterm Evaluation
What happens now is that the system will create a kind of disk image located inside of your external disk called a “sparse bundle”. From now on, Wireless Time Machine will backup and read from the sparse bundle. That’s how Time Machine can interface with the Airport Extreme Base, and it’s probably not the most secure thing on the planet, which may be one of the reasons Apple yanked it.

7) Turn Time Machine back on and instigate test backup

Use either the dock menu or the new menubar item in 10.5.2 to begin test backup.

8) Once test backup is finished, launch Time Machine application

If all went well, your Time Machine should now show a view of the test files you backed up located “in the past”. See Time Machine’s help menu for help on how to use Time Machine. If you don’t see the files, or if you can’t open Time Machine at all, it may mean that your system or hard disk won’t allow for Wireless backup. Before you give up, restart your computer, cycle power on/off to your hard disk and AEB, and redo the steps of this tutorial from the beginning.

9) Eject your Hard Disk and plug directly into your Computer via USB port

You should use the Eject icon when the disk is selected, or use Apple-E. Replug the disk into your computer through its built-in USB port.  You may need to re-select your disk from Time Machine’s Preferences (also located in menu bar).

10) Backup full disk while plugged directly into computer

This will make the initial backup go much faster. Because you reformatted the disk and then created the Sparse Bundle, Time Machine will backup neatly to that disk image instead of directly to the disk. This is why you need a clean disk to begin with. Be patient here: the “Preparing” phase can take up to 5 minutes, but will be much faster with all subsequent backups.

11) Eject disk from Computer and replug into Airport Extreme Base

When you are finished with the direct connect backup, you should eject the disk and plug it back into the AEB. You may need to re-select your disk from Time Machine’s Preferences. Now you can continue using Time Machine wirelessly.