The Dockerfile for this image is available in the Puppet-in-Docker repository.
The simplest way of running the Facter Docker image is to run it without any arguments.
docker run puppet/facter
This isn’t particularly useful, in that it will dump information about the
puppet/facter image and then exit. More usefully, Facter can be run against the host operating system by passing the requisite flags to Docker, generally mounting directories and connecting to the host network.
For example, the following incantation should dump information about a CoreOS host:
docker run --rm --privileged -v /tmp:/tmp --net host -v /etc:/etc -v /var:/var -v /usr:/usr -v /lib64:/lib64 puppet/facter
You can read about all the arguments to Facter on the official documentation.
See the examples repository for fully worked examples, including how to run a full Puppet stack using Docker Compose and using Facter to inventory CoreOS, Atomic and PhotonOS.