empty /etc/resolv.conf when instance is booted up

[Yufen Kuo]

When running docker container directly (not from openstack), it would bind mount the host machine's /etc/resolv.conf file (in the absence of the --dns=IP_ADDRESS..., --dns-search=DOMAIN..., or --dns-opt=OPTION... options)

But running docker container with openstack using nova-docker, the /etc/resolv.conf file is always empty. Running mount command from the container shows the /etc/resolv.conf file is not bind mounted.

From Controller
/var/lib/neutron/dhcp/6ee361ce-b1de-4e4f-acb5-f2abfabb29c1/opts
::::::::::::::
tag:tag0,option:dns-server,10.40.0.5
tag:tag0,option:classless-static-route,169.254.169.254/32,10.40.12.23,0.0.0.0/0,10.40.12.1
tag:tag0,249,169.254.169.254/32,10.40.12.23,0.0.0.0/0,10.40.12.1
tag:tag0,option:router,10.40.12.1

From Compute Host
docker inspect <container-id>
            "Dns": [
                "10.40.0.5"
            ],

Setting DOCKER_OPTS --dns setting in /etc/default/docker file still gets empty /etc/resolv.conf
DOCKER_OPTS="--dns 10.40.0.5 --dns 10.0.0.5"