Docker

Ansible role to install and configure Docker container engine on RHEL/CentOS 7.

Main features:

• Supports overlay2 and devicemapper (with direct LVM) Docker storage drivers.
• Uses container-storage-setup (also known as docker-storage-setup) to set up Docker's storage.
• Prevents users from running devicemapper driver on a loopback device by default.
• Sets up convenient passwordless sudo access for running Docker for selected users as recommended by Dan Walsh, lead of Red Hat's Docker team.
• Supports authenticating with private Docker registries.

Limitations:

• Automatically applying changes to the Docker storage configuration for an existing system is not supported. You will have to manually remove the contents of the /var/lib/docker directory and then run the role again.

Requirements

This role requires Ansible 2.4 or higher.

It also requires RHEL/CentOS 7.4 or higher since OverlayFS support for SELinux has been added in that version.

Role Variables

Variables in defaults/main.yml:

Name	Type	Description
docker_storage_driver	string	Storage driver to be used with Docker. It can be one of the following: overlay2: Use OverlayFS. devicemapper: Use Device Mapper kernel framework. "": Don't do any storage setup with docker-storage-setup. NOTE: The overlay storage driver is omitted since overlay2 is more performant.
docker_storage_volumegroup	string	Name of the LVM volume group to use for Docker storage. NOTE: If the value is "", the role will not configure Docker storage's volume group. NOTE: This variable must be changed from the default value if the docker_storage_driver variable is set to devicemapper.
docker_sudo_users	list	List of users for which to configure passwordless sudo access for running Docker of the form: name: string test (optional): boolean where name represents user's name and test indicates whether to test that convenience alias for running Docker works (defaults to true).
docker_private_registries	list	List of private Docker registries with which to authenticate the current system user of the form: registry_url: string username: string password: string email: string where registry_url (optional) represents registry's URL, username represents user name with which to authenticate with the registry, password represents the user's password and email (optional) represents the user's email address. NOTE: email is required when authenticating with Docker Hub.

Dependencies

None.

Example Playbook

- hosts: all

  vars:
    docker_storage_volumegroup: dockervg
    docker_sudo_users:
      - alice
      - bob

  roles:
    - docker

License

GPLv3

Author Information

Tadej Janež

Acknowledgement

This Ansible role was originally developed for Genialis. With approval from Genialis, the code was generalised and published as Open Source, for which the author would like to express his gratitude.