This rooting method relies on using a modified boot image, loaded through fastboot, to mount the system partition as writable. This will not work for the 1st-gen Fire TV or Fire TV Stick because they are hardware locked to not allow fastboot to load a boot image. Oddly, the 2nd-gen Fire TV will allow fastboot to load a boot image, so it may be possible to root the 2nd-gen Fire TV using this method. The problem is, we do not have a complete original boot image for the 2nd-gen Fire TV to use as the base for the modified boot image. The boot image is normally extracted from the software update file, but since the 2nd-gen Fire TV switched to incremental updates, its updates do not contain a complete boot image. Only patches to the boot image.