This repo Dockerfile is a minimal example for Fortran developers. Docker shares the kernel of the host operating system, so that from a Linux host one can run many types and versions of Linux distros. This example shows Ubuntu 18.04 Docker container with OpenCoarrays on a Travis-CI Ubuntu 14.04 host. CentOS 6 and CentOS 7 on Travis-CI using Docker containers has been demonstrated previously.

Specifically, this example docker pull a Docker image previously build from this Dockerfile, compiles the Fortran coarray example and runs a multi-image coarray Fortran test on Travis-CI. This Docker container runs as non-root user with sudo privileges.

Note: this is not necessary for running this example, but just for general information.

Although Travis-CI can also build and deploy (upload) Docker images, to simplify the example, we use a pre-built Docker image. Here's one way to manually build and deploy a Docker image:

1. configure a file Dockerfile with the desired setup. The Dockerfile in this repo sets up Ubuntu 18.04 on many Linux distros or a Windows host.
2. build the Docker image. This will automatically download the base Ubuntu 18.04 image if needed.

   docker build -t test .

3. Instantiate the container in interactive mode, confirm you have the needed programs. If any need to be added, edit Dockerfile, exit / stop this container, and rebuild the container.

   docker run -it test

4. cleanup unused and stopped containers by

   docker system prune

1. instantiate a new Docker container from the image

   docker build -t opencoarrays_fortran .
   
   docker run opencoarrays_fortran

2. commit the image state

   docker commit -m "your commit message" container_hex_id dockerhub_username/opencoarrays_fortran

3. push to DockerHub, where it becomes publicly available

   docker push dockerhub_username/opencoarrays_fortran

Please see .travis.yml for a complete example. The chown statement is necessary because Travis' default UID is 2000, while most Linux default UID is 1000. It seemed better to chown a couple Travis folders rather than remake the image.