Docker DNS with BIND

docker-dns-console.txt

# From HOST the IP is correctly resolved 'mysql.example.com' with the correct address <===

ubuntu@docker:~$ host mysql.example.com 172.17.0.1
Using domain server:
Name: 172.17.0.1
Address: 172.17.0.1#53
Aliases: 

mysql.example.com has address 172.17.0.10


# My /etc/default/docker configuration (and yes: I did a service docker restart)

DOCKER_OPTS="--dns 172.17.0.1 --dns 8.8.8.8"


# Now try to fire up a container pointing at the correct DNS with search domain set up to 'example.com'

$ ubuntu@docker:~$ docker run --dns=172.17.0.1 --dns-search=example.com -h mysql.example.com -it ubuntu:trusty


# Inside the newly started container the hostname is correctly set up

root@mysql:/# hostname
mysql.example.com


# Inside my container the 'resolv.conf' is correctly set up

root@mysql:/# cat /etc/resolv.conf 
search example.com
nameserver 172.17.0.1


# Still, the container has not been able to be assigned with the IP from configured DNS !?!?!

root@mysql:/# ip a
92: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.2/16 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe11:2/64 scope link 
       valid_lft forever preferred_lft forever



# Now, I installed DnsUtils inside the container

root@mysql:/# apt-get install dnsutils
Reading package lists... Done
[..cut..]
The following NEW packages will be installed:
  bind9-host dnsutils geoip-database krb5-locales libbind9-90 libdns100
  libgeoip1 libgssapi-krb5-2 libisc95 libisccc90 libisccfg90 libk5crypto3
  libkeyutils1 libkrb5-3 libkrb5support0 liblwres90 libxml2 sgml-base xml-core
0 upgraded, 19 newly installed, 0 to remove and 0 not upgraded.
[..cut..]



# And finally, made a simple host lookup; which resolves the correct address

root@mysql:/# host mysql.example.com
mysql.example.com has address 172.17.0.10


# ==> The question remains: how come the container is designated with a wrong host ip !?!? <==


# Resolution figured out. Please check out the Docker Forums post: https://forums.docker.com/t/unable-to-resolve-a-container-hostname-with-correct-ip-from-dns/7188