Enable USB on the Apple TV

Note: This Tutorial assumes you’re using AppleTV TakeTwo or the latest update (3.0).

Step 1: Unlock your ATV

This is a pretty easy process, you can find instructions here. You don’t actually have to install Boxee but follow the instructions except instead of creating a boxee USB you can just select “SSH”.
Alternatively you could to unlock the Apple TV using Seas0nPass.
Step by step instructions can be found here and here.
If you wish you install XBMC/Boxee, follow my other post “Watch any video on Apple TV 1”
(Note: Remember that if you do unlock your Apple products, your guarantee with Apple will no longer be valid. But updating the product or restoring it to factory settings will revert it to its default unlocked settings)

Step 2: Install NitoTV

There are lots of ways to enable USB, but this is the easiest. SSH onto your AppleTV, download NitoTV and install it. Here’s the code:
$ ssh frontrow@appletv.local
Welcome to the AppleTV (via atv-usbcreator)
frontrow@appletv.local's password: (default password is frontrow)
-bash-2.05b$ wget http://nitosoft.com/nitoTVInstaller_tt.zip
-bash-2.05b$ unzip nitoTVInstaller_tt.zip
-bash-2.05b$ cd "nitoTV Take Three"/
-bash-2.05b$ sudo ./installme
Note: For instructions on SSH, refer to my post “Enabling Airplay on Apple TV 1”

This will install NitoTV and then restart your AppleTV’s finder, in other words you will have new options on your ATV menu.

Step 3: Prep for USB

Because the apple tv is purposely neutered you’ll need to snag the USB drivers from the 10.4.9 combo update. Here’s the code
-bash-2.05b$ cd ~/Documents/
-bash-2.05b$ wget http://supportdownload.apple.com/download.info.apple.com/Apple_Support_Area/Apple_Software_Updates/Mac_OS_X/downloads/061-3165.20070313.iU8y4/MacOSXUpdCombo10.4.9Intel.dmg

Step 4: Install USB support

Great, now the combo update has been downloaded to the Documents folder. Go to your Apple TV menu and go NitoTV -> Settings -> Install Software -> Smart Installer
This will take a minute but when it’s done you can plugin USB drives and your Apple TV will recognize it. Volia!
If your Apple TV doesn’t recognize your drive try restarting your appletv either by typing “sudo reboot” or unplugging and plugging in your ATV.

SOURCE: http://www.todaywasawesome.com/enable-usb-on-the-apple-tv/