deb http://deb.debian.org/debian/ stretch main contrib non-free
#deb-src http://deb.debian.org/debian/ stretch main contrib non-free

deb http://deb.debian.org/debian/ stretch-updates main contrib non-free
#deb-src http://deb.debian.org/debian/ stretch-updates main contrib non-free

deb http://security.debian.org/ stretch/updates main contrib non-free
#deb-src http://security.debian.org/ stretch/updates main contrib non-free

deb http://deb.debian.org/debian/ stretch-backports main contrib non-free
#deb-src http://deb.debian.org/debian/ stretch-backports main contrib non-free