Update instructions on using Docker container

[aowen-uwmad]

Proposal

1. Make the "Docker Installation Instructions" page more visible on the website.
   • Ideally, put a "Docker" link in the top-level "Getting Started" navigation menu.
   • List "Docker" as a separate line item in the "Installation" page instead of a parenthetical to the "Windows" line.
   • Include a link to the Docker instructions on the DockerHub page.
   • Perhaps include a link to the Docker instructions in the top-level README of the repository?
2. Update the "Docker Installation Instructions" page to include a section about non-"standard" launching of container.
   • Just need to say somewhere to run source /environment?

Background

I was helping a user with launching the official Docker container (https://hub.docker.com/r/idaholab/tmap8) on our computing cluster. While the container worked as expected when launched on their personal computer, it did not work the way we launch containers on our cluster.

On our cluster, we effectively do a version of this command:

docker run --user $(id -u):$(id -g) --rm=true -it \
  -v $(pwd):/scratch -w /scratch \
  idaholab/tmap8:latest /bin/bash

From what I can tell, the useful bits for setting up the TMAP8 environment come from the files loaded automatically by a bash login shell. But since this user's UID is not mapped inside the container, the process can't do the full login.

With some more digging after launching the container on my personal device as "normal", it looks like the login is running source /environment to get the necessary bits in place. So running the above user-specific docker command followed by

source /environment

appeared to work as intended on our cluster.

I'm not sure if that is the only thing that the login files have been setup to do, however. It would be good for whoever setup this Docker container to validate this action and to update the Docker Installation Instructions page with the appropriate instructions.

Also, I did not find the Docker Installation Instructions page in the website until after I searched the repository itself, which led me to the appropriate html address. I did notice after the fact that it is linked in the main Installation page, but it's not obvious.