The default docker.io package in Debian 10 (buster) is broken. I used puppet and the puppetlabs-docker module to install the testing version of docker-ce. I then configured the Plex Media Server as a docker container also using puppet.

1. Run the following commands as root to install puppet

# wget http://apt.puppet.com/puppet5-release-$(lsb_release -sc).deb

# dpkg -i puppet5-release-$(lsb_release -sc).deb

# apt update

# apt install puppet

2. Install the puppetlabs-docker module

# puppet module install puppetlabs-docker

3. Create a puppet manifest

docker.pp

class { 'docker':
  docker_ce_channel => 'test'
}

4. Apply the docker.pp puppet manifest to install and configure docker

# puppet apply --test docker.pp

5. Example: install and run the linuxserver/plex container by appending to the docker.pp file and applying the declarative manifest.

docker.pp

docker::run { 'plex':
  image => 'linuxserver/plex',
  net => 'host',
  env => [
    "PUID=1000",
    "PGID=1000",
    "VERSION=docker",
  ],
  volumes => [
    "/var/lib/plex/config:/config",
    "/data/tv:/tv",
    "/data/movies:/movies",
  ],
}

Create the directories and set the owner to match the UID of the container

# mkdir -p /var/lib/plex/config /data/tv /data/movies

# chown -R 1000:1000 /var/lib/plex/config /data/tv /data/movies

# puppet apply --test docker.pp

6. You can then browse to the Plex webUI at http://raspberry.pi.ip.address:32400