deb http://archive.ubuntu.com/ubuntu/ xenial main restricted universe
deb-src http://archive.ubuntu.com/ubuntu/ xenial main restricted universe

deb http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted universe
deb-src http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted universe

deb http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted
deb-src http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted

deb http://archive.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse