neurons firing from a keyboard

thoughts about devops, technology, and faster business from a random guy from dallas.

Getting output from Docker containers from within Ansible

Reading Time: Approximately 1 minutes.
View this post on GitHub.

The Problem

You want to use Ansible’s docker_container module to do stuff, but want to also perform actions based on their output without specifying a logging driver or writing to a temp file.

The Solution

Do this:

- name: Run a Docker container
    image: alpine
    entrypoint: sh
    command: -c echo "Hello, from Docker"'!'
    detach: false
  register: container_output

- name: Get its output
    msg: "Docker said: {{ container_output.ansible_facts.docker_container.Output }}"

WTF did you just do?

The key takeaways:

  • docker_container runs its containers in detached mode by default. We turned this off by specifying detach: false

  • The container’s metadata (i.e. the stuff you get from docker output</code> are exposed as Ansible facts, which are captured by registering the play first. <code>container_output.ansible_facts.docker_container.Output</code> captures the fact that contains our <code>stdout.