Manage environment variables in Docker configurations with appropriate scope, placement, and documentation:

1. Set environment variables with appropriate scope:
   • Use variables only where needed, not globally
   • Set temporary variables like DEBIAN_FRONTEND only within the commands that need them: ```dockerfile

     Do this:

     RUN apt-get update
     && DEBIAN_FRONTEND=noninteractive apt-get install -y –no-install-recommends
     package1 package2

   Not this:

   ENV DEBIAN_FRONTEND=noninteractive RUN apt-get update && apt-get install -y package1 package2 ```

2. Place variables logically:
   • Group related variables under descriptive comments
   • Place variables near their related commands
   • Use ARG instead of ENV for build-time values, especially versions:

     # version details
     ARG LIBFABRIC_VERSION="1.20.0"
     ARG PYTORCH_VERSION="2.2.2"
     

3. Document variables properly:
   • Add comments explaining non-obvious configurations
   • Include links to relevant documentation when appropriate
   • Document compatibility requirements:

     # Gaudi does not currently support Python 3.11, so we downgrade to 3.10
     # https://docs.habana.ai/en/latest/Support_Matrix/Support_Matrix.html
     

4. Clean up unnecessary variables:
   • Remove obsolete or unused environment variables
   • Consider using dedicated configuration files under /etc/ instead of environment variables when appropriate