Network calls fail during image build on corporate

Question

I'm having a problem building Docker images on my corporate network. I'm just getting started with Docker, so I have the following Dockerfile for a hello-world type app:

# DOCKER-VERSION 0.3.4
FROM    centos:6.4
# Enable EPEL for Node.js
RUN     rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
# Install Node.js and npm
RUN     yum install -y npm
# Bundle app source
ADD . /src
# Install app dependencies
RUN cd /src; npm install
EXPOSE  8080
CMD ["node", "/src/index.js"]

This works fine when I build it on my laptop at home, on my own wireless network. It pulls down the requisite dependencies and builds the image correctly.

However, when I'm on my corporate network at work, this same docker build fails when trying to pull down the RPM from download.fedoraproject.org, with this error message:

Step 2 : RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm ---> Running in e0c26afe9ed5 curl: (5) Couldn't resolve proxy 'some.proxy.address' error: skipping http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm - transfer failed

On my corporate network, I can access that URL just fine from my laptop. But once Docker is trying to build the container, all of a sudden it can't resolve at all. This behavior is the same for a variety of external resources (apt-get, etc.): They all can resolve just fine on my laptop on the corporate network, but Docker can't resolve them.

I don't have the network know-how to figure out what's going on here. Does anyone know why this strange behaviour would be occurring when building Docker containers?

Answer 1

Docker (at least >=1.13, probably earlier) on Mac and Windows allow you configure the DNS in Preferences -> Daemon -> Advanced:

The following config sets two corporate DNS servers (use your own values here) with fallback to Google public DNS servers.