DNS
https://habrahabr.ru/post/303446/
https://tools.ietf.org/html/rfc1912

http://rosenberg.io/2014/08/08/docker-boot2docker-and-dns-resolution-of-containers.html

/etc/nsswitch.conf
    (man nsswitch.conf)
...
hosts:      files dns
networks:   files
...

package: dnsutils
utils:
    dig
    host
    nslookup

/etc/hosts
/etc/resolv.conf

nslookup <host>
    look-up for the host