Debian - Truly Unattended Upgrades

This will make sure you bypass those pesky questions, with the safest option. For when you want to do an upgrade in a script (such as from a Vagrant :shell provision)

DEBIAN_FRONTEND=noninteractive apt-get -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" dist-upgrade