機械設計工程系 DNS 伺服器
https://www.hiroom2.com/2018/05/06/ubuntu-1804-bind-en/
https://help.ubuntu.com/lts/serverguide/dns-configuration.html.en
https://www.linuxtechi.com/install-configure-bind-9-dns-server-ubuntu-debian/
電腦伺服器的名稱伺服, 源自三個動機:
https://superuser.com/questions/1318220/ubuntu-18-04-disable-dnsmasq-base-and-enable-full-dnsmasq
https://askubuntu.com/questions/907246/how-to-disable-systemd-resolved-in-ubuntu/907249#907249
https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html
https://www.server-world.info/en/note?os=Ubuntu_18.04&p=dns&f=1
BIND9 (2005): https://link.springer.com/book/10.1007/978-1-4302-0050-5
BIND10 (2011): https://link.springer.com/book/10.1007/978-1-4302-3049-6
systemctl status bind9
https://www.howtoinstall.me/ubuntu/18-04/nsd/
http://manpages.ubuntu.com/manpages/bionic/man5/nsd.conf.5.html
dnsmasq
http://www.thekelleys.org.uk/dnsmasq/doc.html
local DNS stub listener
https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html
https://askubuntu.com/questions/278448/how-to-know-what-program-is-listening-on-a-given-port