What is ansible-docker?

It is an Ansible role to:

• Install Docker (editions, channels and version pinning are all supported)
• Install Docker Compose using PIP (version pinning is supported)
• Install the docker PIP package so Ansible's docker_* modules work
• Manage Docker registry login credentials
• Configure 1 or more users to run Docker without needing root access
• Configure the Docker daemon's options and environment variables
• Configure a cron job to run Docker clean up commands

Why would you want to use this role?

If you're like me, you probably love Docker. This role provides everything you need to get going with a production ready Docker host.

By the way, if you don't know what Docker is, or are looking to become an expert with it then check out Dive into Docker: The Complete Docker Course for Developers.

Supported platforms

• Ubuntu 18.04 LTS (Bionic)
• Ubuntu 20.04 LTS (Focal Fossa)
• Debian 9 (Stretch)
• Debian 10 (Buster)

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Quick start

The philosophy for all of my roles is to make it easy to get going, but provide a way to customize nearly everything.

What's configured by default?

The latest Docker CE and Docker Compose will be installed, Docker disk clean up will happen once a week and Docker container logs will be sent to journald.

Example playbook

---

# docker.yml

- name: Example
  hosts: "all"
  become: true

  roles:
    - role: "nickjj.docker"
      tags: ["docker"]

Usage: ansible-playbook docker.yml

Installation

$ ansible-galaxy install nickjj.docker

Default role variables

Installing Docker

Edition

Do you want to use "ce" (community edition) or "ee" (enterprise edition)?

docker__edition: "ce"

Channel

Do you want to use the "stable", "edge", "testing" or "nightly" channels? You can add more than one (order matters).

docker__channel: ["stable"]

Version

• When set to "", the current latest version of Docker will be installed
• When set to a specific version, that version of Docker will be installed and pinned

docker__version: ""

# For example, pin it to 20.10.
docker__version: "20.10"

# For example, pin it to a more precise version of 20.10.
docker__version: "20.10.7"

Pins are set with * at the end of the package version so you will end up getting minor and security patches unless you pin an exact version.

Upgrade strategy

• When set to "present", running this role in the future won't install newer versions (if available)
• When set to "latest", running this role in the future will install newer versions (if available)

docker__state: "present"

Downgrade strategy

The easiest way to downgrade would be to uninstall the Docker package manually and then run this role afterwards while pinning whatever specific Docker version you want.

# An ad-hoc Ansible command to stop and remove the Docker CE package on all hosts.
ansible all -m systemd -a "name=docker-ce state=stopped" \
  -m apt -a "name=docker-ce autoremove=true purge=true state=absent" -b

Installing Docker Compose

Docker Compose will get PIP installed inside of a Virtualenv. This is covered in detail in another section of this README file.

Version

• When set to "", the current latest version of Docker Compose will be installed
• When set to a specific version, that version of Docker Compose will be installed and pinned

docker__compose_version: ""

# For example, pin it to 1.29.
docker__compose_version: "1.29"

# For example, pin it to a more precise version of 1.29.
docker__compose_version: "1.29.2"

Upgrade and downgrade strategies will be explained in the other section of this README.

Configuring users to run Docker without root

A list of users to be added to the docker group.

Keep in mind this user needs to already exist, this role will not create it. If you want to create users, check out my user role.

This role does not configure User Namespaces or any other security features by default. If the user you add here has SSH access to your server then you're effectively giving them root access to the server since they can run Docker without sudo and volume mount in any path on your file system.

In a controlled environment this is safe, but like anything security related it's worth knowing this up front. You can enable User Namespaces and any other options with the docker__daemon_json variable which is explained later.

# Try to use the sudo user by default, but fall back to root.
docker__users: ["{{ ansible_env.SUDO_USER | d('root') }}"]

# For example, if the user you want to set is different than the sudo user.
docker__users: ["admin"]

Configuring Docker registry logins

Login to 1 or more Docker registries (such as the Docker Hub).

# Your login credentials will end up in this user's home directory.
docker__login_become_user: "{{ docker__users | first | d('root') }}"

# 0 or more registries to log into.
docker__registries:
  - #registry_url: "https://index.docker.io/v1/"
    username: "your_docker_hub_username"
    password: "your_docker_hub_password"
    #email: "your_docker_hub@emailaddress.com"
    #reauthorize: false
    #config_path: "$HOME/.docker/config.json"
    #state: "present"
docker__registries: []

Properties prefixed with * are required.

• registry_url defaults to https://index.docker.io/v1/
• *username is your Docker registry username
• *password is your Docker registry password
• email defaults to not being used (not all registries use it)
• reauthorize defaults to false, when true it updates your credentials
• config_path defaults to your docker__login_become_user's $HOME directory
• state defaults to "present", when "absent" the login will be removed

Configuring the Docker daemon options (json)

Default Docker daemon options as they would appear in /etc/docker/daemon.json.

docker__default_daemon_json: |
  "log-driver": "journald"

# Add your own additional daemon options without overriding the default options.
# It follows the same format as the default options, and don't worry about
# starting it off with a comma. The template will add the comma if needed.
docker__daemon_json: ""

Configure the Docker daemon options (flags)

Flags that are set when starting the Docker daemon cannot be changed in the daemon.json file. By default Docker sets -H unix:// which means that option cannot be changed with the json options.

Add or change the starting Docker daemon flags by supplying them exactly how they would appear on the command line.

# Each command line flag should be its own item in the list.
#
# Using a Docker version prior to 18.09?
#   You must set `-H fd://` instead of `-H unix://`.
docker__daemon_flags:
  - "-H unix://"

If you don't supply some type of -H flag here, Docker will fail to start.

Configuring the Docker daemon environment variables

docker__daemon_environment: []

# For example, here's how to set a couple of proxy environment variables.
docker__daemon_environment:
  - "HTTP_PROXY=http://proxy.example.com:80"
  - "HTTPS_PROXY=https://proxy.example.com:443"

Configuring advanced systemd directives

This role lets the Docker package manage its own systemd unit file and adjusts things like the Docker daemon flags and environment variables by using the systemd override pattern.

If you know what you're doing, you can override or add to any of Docker's systemd directives by setting this variable. Anything you place in this string will be written to /etc/systemd/system/docker.service.d/custom.conf as is.

docker__systemd_override: ""

Configuring Docker related cron jobs

By default this will safely clean up disk space used by Docker every Sunday at midnight.

# `a` removes unused images (useful in production).
# `f` forces it to happen without prompting you to agree.
docker__cron_jobs_prune_flags: "af"

# Control the schedule of the docker system prune.
docker__cron_jobs_prune_schedule: ["0", "0", "*", "*", "0"]

docker__cron_jobs:
  - name: "Docker disk clean up"
    job: "docker system prune -{{ docker__cron_jobs_prune_flags }} > /dev/null 2>&1"
    schedule: "{{ docker__cron_jobs_prune_schedule }}"
    cron_file: "docker-disk-clean-up"
    #user: "{{ (docker__users | first) | d('root') }}"
    #state: "present"

Properties prefixed with * are required.

• *name is the cron job's description
• *job is the command to run in the cron job
• *schedule is the standard cron job format for every Sunday at midnight
• *cron_file writes a cron file to /etc/cron.d instead of a user's individual crontab
• user defaults to the first docker__users user or root if that's not available
• state defaults to "present", when "absent" the cron file will be removed

Configuring the APT package manager

Docker requires a few dependencies to be installed for it to work. You shouldn't have to edit any of these variables.

# List of packages to be installed.
docker__package_dependencies:
  - "apt-transport-https"
  - "ca-certificates"
  - "cron"
  - "gnupg2"
  - "software-properties-common"

# Ansible identifies CPU architectures differently than Docker.
docker__architecture_map:
  "x86_64": "amd64"
  "aarch64": "arm64"
  "aarch": "arm64"
  "armhf": "armhf"
  "armv7l": "armhf"

# The Docker GPG key id used to sign the Docker package.
docker__apt_key_id: "9DC858229FC7DD38854AE2D88D81803C0EBFCD88"

# The Docker GPG key server address.
docker__apt_key_url: "https://download.docker.com/linux/{{ ansible_distribution | lower }}/gpg"

# The Docker upstream APT repository.
docker__apt_repository: >
  deb [arch={{ docker__architecture_map[ansible_architecture] }}]
  https://download.docker.com/linux/{{ ansible_distribution | lower }}
  {{ ansible_distribution_release }} {{ docker__channel | join (' ') }}

Installing Python packages with Virtualenv and PIP

Configuring Virtualenv

Rather than pollute your server's version of Python, all PIP packages are installed into a Virtualenv of your choosing.

docker__pip_virtualenv: "/usr/local/lib/docker/virtualenv"

Installing PIP and its dependencies

This role installs PIP because Docker Compose is installed with the docker-compose PIP package and Ansible's docker_* modules use the docker PIP package.

docker__pip_dependencies:
  - "gcc"
  - "python3-setuptools"
  - "python3-dev"
  - "python3-pip"
  - "virtualenv"

Installing PIP packages

docker__default_pip_packages:
  - name: "docker"
    state: "{{ docker__pip_docker_state }}"
  - name: "docker-compose"
    version: "{{ docker__compose_version }}"
    path: "/usr/local/bin/docker-compose"
    src: "{{ docker__pip_virtualenv + '/bin/docker-compose' }}"
    state: "{{ docker__pip_docker_compose_state }}"

# Add your own PIP packages with the same properties as above.
docker__pip_packages: []

Properties prefixed with * are required.

• *name is the package name
• version is the package version to be installed (or "" if this is not defined)
• path is the destination path of the symlink
• src is the source path to be symlinked
• state defaults to "present", other values can be "forcereinstall" or "absent"

PIP package state

• When set to "present", the package will be installed but not updated on future runs
• When set to "forcereinstall", the package will always be (re)installed and updated on future runs
• When set to "absent", the package will be removed

docker__pip_docker_state: "present"
docker__pip_docker_compose_state: "present"

Working with Ansible's docker_* modules

This role uses docker_login to login to a Docker registry, but you may also use the other docker_* modules in your own roles. They are not going to work unless you instruct Ansible to use this role's Virtualenv.

At either the inventory, playbook or task level you'll need to set ansible_python_interpreter: "/usr/bin/env python3-docker". This works because this role creates a proxy script from the Virtualenv's Python binary to python3-docker.

You can look at this role's docker_login task as an example on how to do it at the task level.

License

MIT