apt-get in docker behind corporate proxy

Question

I'm attempting to set up a development environment behind a corporate proxy server with Docker. Try as I might, I cannot get the docker container to talk to the proxy server.

The proxy server and apt-get work fine on the host, which is Ubuntu 12.04

The first thing done in the Dockerfile is attempting to set up the proxy variables:

FROM ubuntu
RUN echo 'Acquire::http { Proxy "http://my.proxy.net:8000"; };' >> /etc/apt/apt.conf.d/01proxy
ENV HTTP_PROXY http://my.proxy.net:8000
ENV http_proxy http://my.proxy.net:8000
ENV HTTPS_PROXY https://my.proxy.net:8000
ENV https_proxy https://my.proxy.net:8000
RUN apt-get update && apt-get install -y build-essential

It pulls the image fine, set the variables, but when it gets to apt-get update, it tries for a little while and then fails with:

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/InRelease  
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-updates/InRelease  
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-security/InRelease  
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Could not resolve 'my.proxy.net'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-updates/Release.gpg  Could not resolve 'my.proxy.net'
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/trusty-security/Release.gpg  Could not resolve 'my.proxy.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.

These variables I have set up are consistent with the host linux install (Ubuntu 12.04 on VirtualBox, if that matters)

I also have /etc/default/docker set up with:

export http_proxy="http://my.proxy.net:8000"
export http_proxy="https://my.proxy.net:8000"

Any thoughts?

UPDATE:

It looks like this is an issue with DNS, not necessarily the proxy server. The host /etc/resolve.conf contains:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.0.1
search dhcp.mycompany.com

The host is a virtualbox vm running on a Windows 7 box, and I've found various half-baked solutions that mostly seem to not work. No matter what I try, I can't get it to resolve the hostname of the proxy server

Answer 1

The issue ended up being with DNS. Docker is running on Ubuntu, which is, itself, a Guest OS on VirtualBox. Due to it's own virutalizing mumbo jumbo, it assigned a nameserver of 127.0.0.1 in resolv.conf.

When this happens, Docker will assign itself a DNS nameserver of 8.8.8.8 (google's nameserver) since localhost refers to the docker container not the host.

To fix this, I went all the way out to Windows and ran

ipconfig /all

And got the IP address of my laptops DNS Servers. I added these to DOCKER_OPTS in the configuration file with --dns=my.dns.ip.address and restarted docker, and the other measures I took to get through the proxy worked fine.