https://man.openbsd.org/OpenBSD-6.3/resolv.conf.5
https://mail-index.netbsd.org/port-arm32/1998/10/25/0006.html
https://man7.org/linux/man-pages/man5/resolv.conf.5.html
https://serverfault.com/questions/732325/how-to-persist-resolv-conf-options-such-as-rotate-timeout-in-centos
https://www.freebsd.org/cgi/man.cgi?resolv.conf
https://www.shellhacks.com/setup-dns-resolution-resolvconf-example/