There are two versions of the Dockerfiles, one for Ubuntu Linux and one for
Windows.  Note that the Ubuntu image size is much smaller.


Prerequisites:
1. You need Docker and Docker-compose installed if you're on Linux.
2. You need Docker Desktop installed if you're on a Windows or Mac host.
3. You need to modify "EULA_DATE" in the Dockerfile to specify the date for the
   installer's `accept-EULA` argument.  For example, if the EULA at
   https://www.sidefx.com/legal/license-agreement/ was last updated on
   April 10, 2020, you would set "EULA_DATE" in the Dockerfile to 2020-04-10.
4. To run sesinetd within docker you must have container enabled licenses.
    Regular licenses will not work within containers.

To create a Houdini Docker image:
1. Download a build of Houdini from www.sidefx.com for the container's platform.
4. Navigate to one of the "Ubuntu" or "Windows" folders.
3. Ensure you have set "EULA_DATE" in the Dockerfile.
4. Run `docker-compose build`


Some handy docker-compose commands:
1. `docker-compose run -d -p 1715:1715 sesinetd` will create a container
   running the license server (sesinetd).
2. `docker-compose run hython` will start up hython in the interactive terminal
    running the container.  In the Linux container hython is in
        /opt/hfs[VERSION].
    In the Windows container, hython is in 
        C:/Program Files/Side Effects Software/Houdini[VERSION].
3. `docker-compose build` will build/rebuild the Houdini Docker images.


Some notes about Docker:
1. Docker requires that the Windows image version matches your host's Windows
   version.  The current Windows Houdini image is based on windows:1903; you
   might need to update the Dockerfile accordingly.
2. The Mac and Windows versions do not support the "host" network, but host is
   reachable on the special DNS name "host.docker.internal".  If you have a
   running sesinetd license server on host and would like to connect to it for
   license checkout, you could switch point hserver to it.
3. All platforms (Mac/Linux/Windows) support the Linux version image.  Only
   Windows hosts support the Windows image. 
4. Don't forget to toggle which daemon (Linux or Windows) the Docker CLI talks
   to if you are using Windows Docker Desktop.  You can switch it from the
   Docker Desktop menu by selecting:
       "Switch to Windows containers to use Windows containers" and 
       "Switch to Linux containers to use Linux containers"