sources.listの内容

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

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

# stretch-updates, previously known as 'volatile'
deb http://ftp.jp.debian.org/debian/ stretch-updates main contrib
deb-src http://ftp.jp.debian.org/debian/ stretch-updates main contrib

# stretch-backports, previously on backports.debian.org
deb http://ftp.jp.debian.org/debian/ stretch-backports main
deb-src http://ftp.jp.debian.org/debian/ stretch-backports main