Show some ENV / local updated baseimage tricks that use an apt-cacher-ng proxy to make debian based installations instant

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)

docs/sources/examples/apt-cacher-ng.Dockerfile

@@ -0,0 +1,15 @@
+#
+# BUILD		docker build -t apt-cacher .
+# RUN		docker run -d -p 3142:3142 -name apt-cacher-run apt-cacher
+#
+# and then you can run containers with:
+# 		docker run -t -i -rm -e http_proxy http://dockerhost:3142/ debian bash
+#
+FROM		ubuntu
+MAINTAINER	SvenDowideit@docker.com
+
+VOLUME		["/var/cache/apt-cacher-ng"]
+RUN		apt-get update ; apt-get install -yq apt-cacher-ng
+
+EXPOSE 		3142
+CMD		chmod 777 /var/cache/apt-cacher-ng ; /etc/init.d/apt-cacher-ng start ; tail -f /var/log/apt-cacher-ng/*

docs/sources/examples/apt-cacher-ng.rst

@@ -0,0 +1,104 @@
+:title: Running an apt-cacher-ng service
+:description: Installing and running an apt-cacher-ng service
+:keywords: docker, example, package installation, networking, debian, ubuntu
+
+.. _running_apt-cacher-ng_service:
+
+Apt-Cacher-ng Service
+=====================
+
+.. include:: example_header.inc
+
+
+When you have multiple Docker servers, or build unrelated Docker containers
+which can't make use of the Docker build cache, it can be useful to have a 
+caching proxy for your packages. This container makes the second download of
+any package almost instant.
+
+Use the following Dockerfile:
+
+.. literalinclude:: apt-cacher-ng.Dockerfile
+
+To build the image using:
+
+.. code-block:: bash
+
+    $ sudo docker build -rm -t eg_apt_cacher_ng .
+
+Then run it, mapping the exposed port to one on the host
+
+.. code-block:: bash
+
+    $ sudo docker run -d -p 3142:3142 -name test_apt_cacher_ng eg_apt_cacher_ng
+
+To see the logfiles that are 'tailed' in the default command, you can use: 
+
+.. code-block:: bash
+
+    $ sudo docker logs -f test_apt_cacher_ng
+
+To get your Debian based containers to use the proxy, you can do one of 3 things
+
+1. Set and environment variable: ``http_proxy=http://dockerhost:3142/``
+2. Add an apt Proxy setting ``echo 'Acquire::http { Proxy "http://dockerhost:3142"; };' >> /etc/apt/conf.d/01proxy``
+3. Change your sources.list entries to start with ``http://dockerhost:3142/``
+
+Option 1 will work for running a container, so is good for testing, but will 
+break any non-apt http requests, like ``curl``, ``wget`` and more.:
+
+.. code-block:: bash
+
+    $ sudo docker run -rm -t -i -e http_proxy=http://dockerhost:3142/ debian bash
+
+Or you can inject the settings safely into your apt configuration in a local
+version of a common base:
+
+.. code-block:: bash
+
+    FROM ubuntu
+
+    RUN  echo 'Acquire::http { Proxy "http://dockerhost:3142"; };' >> /etc/apt/apt.conf.d/01proxy
+
+    RUN apt-get update ; apt-get install vim git
+
+    # docker build -t my_ubuntu .
+
+Option 3 is the least portable, but there will be times when you might need to
+do it - and you can do it from your Dockerfile too.
+
+Apt-cacher-ng has some tools that allow you to manage the repository, and they 
+can be used by leveraging the ``VOLUME``, and the image we built to run the 
+service:
+
+.. code-block:: bash
+
+    $ sudo docker run -rm -t -i --volumes-from test_apt_cacher_ng eg_apt_cacher_ng bash
+
+    $$ /usr/lib/apt-cacher-ng/distkill.pl
+    Scanning /var/cache/apt-cacher-ng, please wait...
+    Found distributions:
+    bla, taggedcount: 0
+         1. precise-security (36 index files)
+         2. wheezy (25 index files)
+         3. precise-updates (36 index files)
+         4. precise (36 index files)
+         5. wheezy-updates (18 index files)
+
+    Found architectures:
+         6. amd64 (36 index files)
+         7. i386 (24 index files)
+
+    WARNING: The removal action may wipe out whole directories containing
+             index files. Select d to see detailed list.
+
+    (Number nn: tag distribution or architecture nn; 0: exit; d: show details; r: remove tagged; q: quit): q
+
+
+Finally, clean up after your test by stopping and removing the container, and
+then removing the image.
+
+.. code-block:: bash
+
+    $ sudo docker stop test_apt_cacher_ng
+    $ sudo docker rm test_apt_cacher_ng
+    $ sudo docker rmi eg_apt_cacher_ng

docs/sources/examples/index.rst

@@ -26,3 +26,4 @@ to more substantial services like those which you might find in production.
    using_supervisord
    cfengine_process_management
    python_web_app
+   apt-cacher-ng