page_title: Running an apt-cacher-ng service
page_description: Installing and running an apt-cacher-ng service
page_keywords: docker, example, package installation, networking, debian, ubuntu

# Apt-Cacher-ng Service

> **Note**: 
> 
> - This example assumes you have Docker running in daemon mode. For
>   more information please see [*Check your Docker
>   install*](../hello_world/#running-examples).
> - **If you don't like sudo** then see [*Giving non-root
>   access*](/installation/binaries/#dockergroup).
> - **If you're using OS X or docker via TCP** then you shouldn't use
>   sudo.

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:

    #
    # 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/*

To build the image using:

    $ sudo docker build -t eg_apt_cacher_ng .

Then run it, mapping the exposed port to one on the host

    $ 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:

    $ sudo docker logs -f test_apt_cacher_ng

To get your Debian-based containers to use the proxy, you can do one of
three things

1. Add an apt Proxy setting
   `echo 'Acquire::http { Proxy "http://dockerhost:3142"; };' >> /etc/apt/conf.d/01proxy`
2. Set an environment variable:
   `http_proxy=http://dockerhost:3142/`
3. Change your `sources.list` entries to start with
   `http://dockerhost:3142/`

**Option 1** injects the settings safely into your apt configuration in
a local version of a common base:

    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 2** is good for testing, but will break other HTTP clients
which obey `http_proxy`, such as `curl`, `wget` and others:

    $ sudo docker run --rm -t -i -e http_proxy=http://dockerhost:3142/ debian bash

**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`
instruction, and the image we built to run the service:

    $ 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.

    $ sudo docker stop test_apt_cacher_ng
    $ sudo docker rm test_apt_cacher_ng
    $ sudo docker rmi eg_apt_cacher_ng