After selecting “No automatic updates” in the Ubuntu 16.04 server installer, I expected that the system would not attempt to upgrade anything without my permission, just like every version before. Turns out that is not the case. I found out the hard way when my production database shut down to upgrade in the middle of the day.

You can turn it off totally by editing the following lines in /etc/apt/apt.conf.d/10periodic:

APT::Periodic::Download-Upgradeable-Packages “0”;
APT::Periodic::Download-Upgradeable-Packages-Debdelta “0”;
APT::Periodic::AutocleanInterval “0”;

And editing this line in /etc/apt/apt.conf.d/20auto-upgrades:

APT::Periodic::Unattended-Upgrade “0”;