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# vim /etc/apt/apt.conf.d/50unattended-upgrades
  Unattended-Upgrade::Mail "root";
  # set up the needed behavior
  ...
  
# dpkg-reconfigure -plow unattended-upgrades # -> creates following file:

# editor /etc/apt/apt.conf.d/20auto-upgrades
  APT::Periodic::Update-Package-Lists "1";
  APT::Periodic::Download-Upgradeable-Packages "1";
  APT::Periodic::Unattended-Upgrade "1";
  APT::Periodic::AutocleanInterval "7";