OK. I have spent many hours on aTVFlash and wish someone had told me these things.
The first cardinal rule of hacking is to make sure you can ALWAYS return to a previous state (of working or unworkingness). With aTVFlash hack, it is not obvious how to do this. Since the auto-update on the ATV only updates the ATV firmware to what Apple considers to be the “current” version for all ATVs (2.3 today). Factory Restore only restores to the version that shipped with your ATV when purchased. Say 2.0. What if you are on 2.2 and you want to try 2.3 with aTVFlash 3.4.1 but want the option of returning to 2.2 with 3.3.5?
Anyway, after much reading of posting on this excellent forum, I was able to find the simple method to allow the user to restore the ATV to any past version.
google “How to replace your Apple TV Factory Restore Firmware to 2.0.2 or 2.1” to download the pdf instructions.
Basically, Apple releases (and posts) ATV updates in a dmg format that has a cryptic name like 2Z694-5499.dmg (ATV firmware 2.2). But think of this as the yolk of the ATV firmware (around 180MB). Replacing the yolk updates the firmware of the ATV. But the restore image, stored in a hidden partition on the hard drive of the ATV, contains other material that makes the image bootable. (Rest of the Egg, 400MB total.)
The PDF above shows how you use Unix command to clone the old egg on your ATV (the dd command is like CarbonCopyCloner), FTP it to your Mac, and graft a new yolk (2.2, say) into an old egg (e.g. 1.0).
But just to be able to do this required you to first hacked the ATV so you can ssh to it and clone the “old egg” (restore.img).
So, basically, you have to somehow managed to install some compatible version of aTVFlash to your ATV (whatever you do, do not upgrade your ATV unless you have read this note and understand it fully). It would be nice if Applecorellc would publish a list of aTVFlash versions that are compatible with ATV firmware versions along with a download links to and version numbers corresponding to each of the 2Z694-5499.dmg type ATV update files (yolks that ends up as OS.dmg in the restore image).
Once you have successfully hacked the ATV so at least you can FTP and ssh, then you need to first harvest the existing “egg” or the hidden restore image on the ATV hard drive. Then, you can update the ATV to say 2.2 and apply aTVFlash 3.3.5 to it.
If that combination is stable (so far, so good), and you want to test ATV firmware 2.3 with aTVFlash 3.4.1, but want to make sure you can return to 2.2 with 3.3.5, the only way to do so is to replace the restore image on the ATV hard drive with the 2.2 image by following the PDF instructions. AND not destroying the 3.3.5 usb patchstick.
Wish someone had told me this before.
Also, the OS.dmg needed to create ATV Firmware 1.0 should be made easily accessible by purchasers of ATV 2.0. This image is needed by “Smart Installer” to activate AFP support and possibly USB Keyboard.
Also, if you managed to get the Tiger Combined update image and the Firmware 1.0 image into /Users/frontrow/Documents/ folder for Smart Installer to do its thing, you should remember to run the two sudo commands via ssh to “finish off” the install of AFP and Remote Access.
Finally, if ssh suddenly breaks, you have to remove the known_hosts file in a hidden folder in your Mac “.ssh”, or use another Mac, or assign the ATV manually to a different IP address.