Speed up your installs with a docker-ized apt-cacher-ng

Everyone hates downloading the same package multiple times. It gets even worse when you're doing it constantly when building docker images.

The process of dockerizing apt-cacher-ng is very well documented here. Refer to the link for an in depth read, or continue for a quick sample.

Optionally, you can find a recording
of the process below on asciinema.

We will need to build the docker image first. You can use this Dockerfile

# Taken from: https://docs.docker.com/examples/apt-cacher-ng/
FROM        ubuntu
MAINTAINER  SvenDowideit@docker.com

VOLUME  /var/cache/apt-cacher-ng
RUN     apt-get update && apt-get install -y 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/*

Build it using

$ docker build -t cacher:latest .

When the cacher image is done building, run it using the following:

$ docker run -d -p 3142:3142 --name cacher cacher:latest

Now let's fire (#1) a ubuntu:latest container and make it communicate with our cacher and install a package.

$ docker run --link cacher:cacher -e http_proxy=http://cacher:3142 -ti ubuntu:latest apt-get install -y python 

The first install of a specific package will download it from the internet and cache it. Here's an example excerpt of the log from the cacher:

$ docker logs cacher      
...
1429789936|I|1190396|172.17.0.106|uburep/pool/main/p/python2.7/python2.7-minimal_2.7.6-8_amd64.deb         1429789936|O|1190427|172.17.0.106|uburep/pool/main/p/python2.7/python2.7-minimal_2.7.6-8_amd64.deb
...

Now re-run another container using the same command issued before (ref #1). Notice how instead of downloading from the internet, apt-get retrieves the package instantly from the cacher.