docker - How do you run `apt-get` in a dockerfile behind a proxy?

Question

I am running a virtual machine (Ubuntu 13.10) with docker (version 0.8.1, build a1598d1). I am trying to build an image with a dockerfile. First, I want to update the packages (using the code below - the proxy is obfuscated) but apt-get times out with the error: Could not resolve 'archive.ubuntu.com'.

FROM ubuntu:13.10
ENV HTTP_PROXY <HTTP_PROXY>
ENV HTTPS_PROXY <HTTPS_PROXY>
RUN export http_proxy=$HTTP_PROXY
RUN export https_proxy=$HTTPS_PROXY
RUN apt-get update && apt-get upgrade

I have also run the following in the host system:

sudo HTTP_PROXY=http://<PROXY_DETAILS>/ docker -d &

The host is able to run apt-get without issue.

How can I change the dockerfile to allow it to reach the ubuntu servers from within the container?

Update

I ran the code in CentOS (changing the FROM ubuntu:13.10 to FROM centos) and it worked fine. It seems to be a problem with Ubuntu.

Answer 1

UPDATE:

You have wrong capitalization of environment variables in ENV. Correct one is http_proxy. Your example should be:

FROM ubuntu:13.10
ENV http_proxy <HTTP_PROXY>
ENV https_proxy <HTTPS_PROXY>
RUN apt-get update && apt-get upgrade

or

FROM centos
ENV http_proxy <HTTP_PROXY>
ENV https_proxy <HTTPS_PROXY>
RUN yum update 

All variables specified in ENV are prepended to every RUN command. Every RUN command is executed in own container/environment, so it does not inherit variables from previous RUN commands!

Note: There is no need to call docker daemon with proxy for this to work, although if you want to pull images etc. you need to set the proxy for docker deamon too. You can set proxy for daemon in /etc/default/docker in Ubuntu (it does not affect containers setting).

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Also, this can happen in case you run your proxy on host (i.e. localhost, 127.0.0.1). Localhost on host differ from localhost in container. In such case, you need to use another IP (like 172.17.42.1) to bind your proxy to or if you bind to 0.0.0.0, you can use 172.17.42.1 instead of 127.0.0.1 for connection from container during docker build.

You can also look for an example here: How to rebuild dockerfile quick by using cache?