Docker rootless Ansible role

An Ansible role to configure install and configure a Docker daemon running as a non-root user.

Do not use any of this without first testing in a non-operational environment.

Rootless mode allows running the Docker daemon and containers as a non-root user to mitigate potential vulnerabilities in the daemon and the container runtime. (docker)

Note There is a SLSA artifact present under the slsa action workflow for verification.

Requirements

None.

Playbook example

---
- hosts: all
  any_errors_fatal: true
  tasks:
    - name: Include the konstruktoid.docker_rootless role
      ansible.builtin.import_role:
        name: konstruktoid.docker_rootless

Role Variables with defaults

---
docker_add_alias: true
docker_allow_ping: false
docker_allow_privileged_ports: false
docker_compose: false
docker_compose_release: v2.27.0
docker_compose_release_shasum: f3ba3bf1e4ab18e96c2d36526a075a02a78fb5f8e80d3e3ca9c5bf256d81d0a0
docker_compose_url: https://github.com/docker/compose/releases/download
docker_daemon_json_template: daemon.json.j2
docker_release: 26.1.3
docker_release_rootless_shasum: 864852d0210582ef6618f8f3a1de786c31ec53581541769b0db05d71ebfda97b
docker_release_shasum: a50076d372d3bbe955664707af1a4ce4f5df6b2d896e68b12ecc74e724d1db31
docker_repository_template: docker.repo.j2
docker_rootful_enabled: false
docker_rootful: false
docker_rootful_opts: false
docker_rootful_service_template: docker_rootful.service.j2
docker_rootless_script_template: docker_rootless.sh.j2
docker_rootless_service_template: docker_rootless.service.j2
docker_service_restart: true
docker_url: https://download.docker.com/linux/static/stable/x86_64
docker_user_bashrc: false
docker_user: dockeruser

Before using this role you first have to decide if you want to install Docker using the packages available to the distribution, also known as the "rootful" installation since it requires root permissions and installs the upstream Docker daemon or if you want to download the static binaries and do a manual install.

If you set docker_rootful: false you will download the static binaries and do a manual install, not requiring any root permissions.

If docker_rootful: true, then docker_rootful_enabled will decide if the daemon should be enabled as a service or not.

docker_service_restart will restart the rootless service after the Docker binaries has been extracted. This may affect any running containers.

Using docker_rootful: true and docker_rootful_enabled: true, will result in a standard Docker installation, with an additional Docker daemon, running as a non-root user.

Note that Debian 10 and earlier requires docker_rootful: false due to missing dependencies.

The docker_url, docker_release, docker_compose_url and docker_compose_release variables define where you find the relevant binaries and which version you should use when doing a manual installation.

You define the name of the Docker user that will be created with the docker_user variable. This user will download and install the binaries if docker_rootful: false or else the user will be the one running the rootless installation script and starting a isolated daemon.

Note that the sole purpose of the docker_user is to run the Docker daemon and related containers, and not for system administration or used as a regular user.

docker_release_shasum, docker_release_rootless_shasum and docker_compose_release_shasum are used to verify the files when downloaded using the get_url module. The docker_release_shasum is used for the Docker .tgz file and docker_release_rootless_shasum for the docker-ce-rootless-extras package.

docker_rootful_opts is the options to apply to the Docker daemon if running in rootful mode, if unset the settings in docker_rootful_service_template will be used.

If docker_add_alias: true, then a docker alias will be added to either .bashrc or .bash_aliases of the Ansible user. If false, a shell script named docker_rootless.sh is created in the Ansible user home directory. This works as a substitute to the docker command so that the Ansible user can execute the rootless Docker installation from the docker_user.

If docker_compose: true, then the Docker compose plugin or docker-compose will be installed.

If docker_user_bashrc: true, a .bashrc with completion for the docker and docker compose command will be placed inside the docker_user home.

The docker_allow_privileged_ports variable configures if exposing privileged ports (< 1024) is allowed.

The docker_allow_ping variable configures if unprivileged users can open ICMP echo sockets. On some distributions, this is not allowed, and thereby containers cannot ping to the outside.

The variables named *_template are the locations of the templates in use, this to make it easier to replace them with custom ones.

The most important template is most likely docker_daemon_json_template: daemon.json.j2, which is the location of the Docker daemon.json configuration file template.

Container management

Standalone container

Running containers is not that much different from when a rootful Docker daemon is used, but you still need to become the unprivileged user and adapt any paths to the user working directores.

If docker_add_alias: true is used, the docker command will be available as usual for the Ansible user, too. Type alias in the shell to see the keyword configuration.

- name: Register Docker user info
  become: true
  ansible.builtin.user:
    name: "{{ docker_user }}"
  check_mode: true
  register: docker_user_info

- name: Example container block
  environment:
    XDG_RUNTIME_DIR: "/run/user/{{ docker_user_info.uid }}"
    PATH: "{{ docker_user_info.home }}/bin:{{ ansible_env.PATH }}"
    DOCKER_HOST: "unix:///run/user/{{ docker_user_info.uid }}/docker.sock"
  block:
    - name: Nginx container
      become: true
      become_user: "{{ docker_user }}"
      community.docker.docker_container:
        name: nginx
        image: konstruktoid/nginx
        state: started
        cap_drop: all
        capabilities:
          - chown
          - dac_override
          - net_bind_service
          - setgid
          - setuid
        pull: true
        hostname: "{{ ansible_nodename }}"
        container_default_behavior: compatibility

Docker compose service

- name: Register Docker user info
  become: true
  ansible.builtin.user:
    name: "{{ docker_user }}"
  check_mode: true
  register: docker_user_info

- name: Example docker compose block
  become: true
  become_user: "{{ docker_user }}"
  environment:
    XDG_RUNTIME_DIR: /run/user/{{ docker_user_info.uid }}
    PATH: "{{ docker_user_info.home }}/bin:{{ ansible_env.PATH }}"
    DOCKER_HOST: "unix:///run/user/{{ docker_user_info.uid }}/docker.sock"
  block:
    - name: Install pip dependencies
      ansible.builtin.pip:
        name:
          - docker<7 # https://github.com/docker/docker-py/issues/3194
          - docker-compose

    - name: Create and start services
      community.docker.docker_compose:
        project_src: /var/tmp/
        files: "{{ docker_user }}-docker-compose.yml"
      register: compose_output

Testing with molecule

If Ansible Molecule with the vagrant plugin and related software is installed, running molecule test is supported.

tox -l will list all available tox test environments.

Contributing

Do you want to contribute? Great! Contributions are always youlcome, no matter how large or small. If you found something odd, feel free to submit a issue, improve the code by creating a pull request, or by sponsoring this project.

License

Apache License Version 2.0

Author Information

https://github.com/konstruktoid