2014-10-10 about DNS http://server.riopi.net/bind9.html http://www.tatsuyababa.com/NW-DNS/NW-200308-DNS.pdf http://www.tatsuyababa.com/NW-DNS/ https://www.upken.jp/kb/ubuntu-bind.html https://forums.ubuntulinux.jp/viewtopic.php?id=16090 http://www.atmarkit.co.jp/ait/articles/0112/18/news001.html