[SOLVED] Disable automatic update not working?

[Nachteule]

The question is - where does your /etc/apt/apt.conf.d/20auto-upgrades file came from (answer below)?

I've checked all my XBian's, neither this file appears on my XBian's nor it exists on my standard Debian's - but
it is there in a recent generated XBian image. So, it seams that this was introduced with Debian Stretch [1] - if APT::Periodic::Update-Package-Lists and/or? APT::Periodic::Unattended-Upgrade setting does not exist, this file will be generated by postinst procedure of package unattended-upgrades

So, you can remove /etc/apt/apt.conf.d/20auto-upgrades safely, and I'll think about a solution how to solve this issue permanently

[1] Latest Jessie image does not have this file, so it is new Stretch behavior