Install docker on subset of test machines

[mhdawson]

As discussed in latest build WG meeting, in order to be able to run tests on certains OS's (like Alpine - see #75) we need docker to be installed on a subset of the test machines.

We should likely start by adding it as a dependency in Ansible for our ubuntu 14 machines which are fairly recent and which run docker well.

[jbergstroem]

quick question: how do we then automate installing alpine/similar on top of docker? is it part of the same build script?

[Vanuan]

@jbergstroem distribution installation is always a part of Dockerfiles. No ansible scripts needed. Here's a pull request that passes locally, but fails due to resource constraints:
nodejs/docker-node#156

[Vanuan]

The problematic part is how to publish binaries from docker to https://nodejs.org/dist/ archives.

[Vanuan]

So there are 4 dockerfiles needed:

1. Dockerfile that include build tools to build distributed binaries for each version (release delivery to https://nodejs.org/dist/).
2. Dockerfile that include build tools to build distributed binaries for the latest version (continuous delivery to https://nodejs.org/dist/).
3. Dockerfile that include build tools and test tools to run tests (continuous integration)
4. Dockerfile that include binaries from https://nodejs.org/dist/ and deploy them to Docker Hub (continuous deployment)

1 & 2 could be the same dockerfile, but with a different build context (different source trees).
3 is different in that it includes build and run scripts for tests.
4 is different in that it's mostly a packaging and deployment thing and should be used by end user

[Vanuan]

Number 4 in that list is this: nodejs/docker-node#156
But it should be triggered either regularly by the publish hook to https://nodejs.org/dist/

Number 3 is what this issue is for.

Number 1 & 2 should be handled in #75

[Vanuan]

Number 3 (this issue) is presumably being fixed by #437

[mhdawson]

I think this issue can be closed as the motivation was to get alpine runs into the ci and it looks like they are there.