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Ansible role for creating Systemd services for docker containers
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Docker role mhutter.docker-systemd-service

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Generic role for creating systemd services to manage docker containers.


- name: Start WebApp
    name: mhutter.docker-systemd-service
    container_name: myapp
    container_image: myapp:latest
    container_links: [ 'mysql' ]
      - '/data/uploads:/data/uploads'
      - '3000:3000'
      MYSQL_ROOT_PASSWORD: "{{ mysql_root_pw }}"
      - 'traefik.enable=true'

This will create:

  • A file containing the env vars (either /etc/sysconfig/mysql or /etc/default/mysql).
  • A systemd unit which starts and stops the container. The unit will be called <name>_container.service to avoid name clashes.

Role variables

  • container_name (required) - name of the container

Docker container specifics

  • container_image (required) - Docker image the service uses
  • container_args - arbitrary list of arguments to the docker run command
  • container_cmd - optional command to the container run command (the part after the image name)
  • container_env - key/value pairs of ENV vars that need to be present
  • container_volumes (default: []) - List of -v arguments
  • container_ports (default: []) - List of -p arguments
  • container_link (default: []) - List of --link arguments
  • container_labels (default: []) - List of -l arguments
  • container_docker_pull (default: yes) - whether the docker image should be pulled

Systemd service specifics

  • enabled (default: yes) - whether the service should be enabled
  • masked (default: no) - whether the service should be masked
  • state (default: started) - state the service should be in - set to absent to remove the service.


This role requires the docker python module. Install it with pip3 install docker or apt install python3-docker (or drop the 3 for python 2.x).

Put this in your requirements.yml:

- role: mhutter.docker-systemd-service

and run ansible-galaxy install -r requirements.yml.


  • When the unit or env file is changed, systemd gets reloaded but existing containers are NOT restarted.
  • Make sure to quote values for container_ports, container_volumes and so on, especially if they contain colons (:). Otherwise YAML will interpret them as hashes/maps and ansible will throw up.

About orchestrating Docker containers using systemd.

The concept behind this is to define systemd units for every docker container. This has some benefits:

  • systemd is a well-known interface
  • all services are controllable via the same tool (systemctl)
  • all logs are accessible via the same tool (journalctl)
  • dependencies can be defined
  • startup behaviour can be defined
  • by correctly defining the unit (see below), we can ensure we always have a clean container.

Here is an example myapp_container.service unit file (about what's produced by above code):

# define dependencies

# Load ENV vars from a file. Note that this env vars will only be
# accessible in the context of the Exec* commands, and not within the
# container itself. To make env-vars accessible within the Container, we use
# the `--env-file` flag for the `docker run` command.

# Even though we explicitly run the container using the `--rm` flag, there
# may be leftover containers (eg. after a system-, docker- or app-crash).
# Starting a container with an existing name will always fail.

ExecStartPre=-/usr/bin/docker rm -f myapp

# actually run the container.
# `--name` to identify the container
# `--rm` ensure the container is removed after stopping
# `--env-file` make ENV vars accessible to app
# `--link mysql` link to a container named `mysql`. The DB will then be
#                accesible at `mysql:3306`
# `-v` mount `/data/uploads` into the container
# `-p 3000:3000` expose port 3000 on the network
ExecStart=/usr/bin/docker run --name myapp --rm --env-file /etc/sysconfig/myapp --link mysql -v /data/uploads:/data/uploads -p 3000:3000
# note that there is no `--restart` parameter. This is because restarting
# is taken care of by `systemd`.

# Stop command.
ExecStop=/usr/bin/docker stop myapp

# Ensure log messages are correctly tagged in the system log.

# Auto-Restart the container after a crash.

# make sure service is started after docker is up
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