docker-compose build
docker-compose up
The container doesn't automatically run drush site-install because we want it to be possible to stop and start an existing container without rebuilding the site every time. Instead, you need to manually run this after starting the container the first time:
docker exec contentadocker_php_1 init-drupal
In the above command, "contentadocker_php_1" is the name of the running container for the php service. If docker-compose names yours differently, you can find it with docker-compose ps.
When it finishes successsfully, the command will output a one-time login URL.
Persistent state is stored in two docker volumes (named data and www). You can destroy and recreate the containers as much as you like and your site will be preserved until you also destroy these volumes.