List Installed Packages
#apt list –installed
Keys
apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 1657198823E52A61
Installing old version of debian
apt-get --allow-unauthenticated upgrade
set permantly
goto /etc/apt/apt.conf.d/
create 99myown
inclued the following APT::Get::AllowUnauthenticated "true";