I've been using auto update for a while, but recently I discovered the downloaded package cache missing in
/var/cache/apt/archives, some deb packages, like Skype, are removed, and I don't know why.
So I'm thinking about this option:
APT::Periodic::AutocleanInterval, currently set to
This page didn't provide much information: https://help.ubuntu.com/community/AutomaticSecurityUpdates