Arvados

Adding the --pull switch would help ensure that you're actually installing the latest version, just in case the local Docker daemon has an older version already. It's a judgment call, though, as to whether it's "required."

I think we should add the --pull flag as Brett suggested. That way the text "The following command downloads the latest arvados/jobs image from Docker Hub" will be true.

With that change, 9677-update-install-docs LGTM.