deb-src http://ftp.de.debian.org./debian buster main contrib non-free deb-src http://ftp.de.debian.org./debian buster-updates main contrib non-free deb-src http://ftp.de.debian.org./debian buster-proposed-updates main contrib non-free deb-src http://security.debian.org./debian-security buster/updates main contrib non-free deb-src http://ftp.de.debian.org./debian buster-backports main contrib non-free