Setting Up Docker Dnsmasq

Question

I\'m trying to set up a docker dnsmasq container so that I can have all my docker containers look up the domain names rather than having hard-coded IPs (if they are on the same

Answer 1

The build script for the docker dnsmasq service needs to be changed in order to bind to your server's public IP, which in this case is 192.168.1.12 on my eth0 interface

#!/bin/bash

NIC="eth0"

name="dnsmasq_"
timenow=$(date +%s)
name="$name$timenow"

MY_IP=$(ifconfig $NIC | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}')


sudo docker run \
-v="$(pwd)/dnsmasq.hosts:/dnsmasq.hosts" \
--name=$name \
-p=$MY_IP:53:5353/udp \
-d sroegner/dnsmasq

On the host (in this case ubuntu 12), you need to update the resolv.conf or /etc/network/interfaces file so that you have registered your public IP (eth0 or eth1 device) as the nameserver.

You may want to set a secondary nameserver to be google for whenever the container is not running, by changing the line to be dns-nameservers xxx.xxx.xxx.xxx 8.8.8.8 E.g. there is no comma or another line.

You then need to restart your networking service sudo /etc/init.d/networking restart if you updated the /etc/network/interfaces file so that this auto updates the /etc/resolve.conf file that docker will copy to the container during the build.

Now restart all of your containers

• sudo docker stop $CONTAINER_ID
• sudo docker start $CONTAINER_ID

This causes their /etc/resolv.conf files update so they point to the new nameserver settings.

DNS lookups in all your docker containers (that you built since making the changes) should now work using your dnsmasq container!

As a side note, this means that docker containers on other hosts can also take advantage of your dnsmasq service on this host as long as their host's nameserver settings is set to using this server's public IP.