If you have encountered iTunes error 9006 when either upgrading to the latest Apple firmware, iOS 8.1.2 at the moment, there’s no need to be frustrated, we can help you solve this issue.
You’ll need to download your IPSW for the device you’re trying to update to, and simply restore it manually.
Step 1. Download your IPSW at ipsw.me
Step 2. Open up iTunes and select your device.
Step 3. If you’re on a PC hold down shift, option if you’re on a Mac.
Step 4. Tap restore and search for the IPSW your download.
Step 5. Tap restore once again, now give iTunes a couple minutes so it can do its thing.
Let me know if this worked for you down below in the comments section.