Additionally, `y2update.tgz` in the root of the add-on media should contain all files that are need for the installation itself. Both for the first stage installation and also for the running system. See https://github.com/yast/yast-packager/blob/8a10630743997648dee499eb51752946951ba241/src/modules/AddOnProduct.rb#L576

@mvidner We still support y2update for this scenario, correct?