Instance environment persistence unclear

[tsnowlan]

Which Document page:

On what page is the problem? Running Services, Environment and Metadata

Expected results:

What are you expecting to see?

An explanation of how environment variables persist when using singularity instances.

Actual results:

What is the problem, what's misspelled, or what's missing?

Environment variables set at instance start are not persisted to singularity exec|shell commands run on that instance. This seems to be by design (ref: hpcng/singularity#5353) but is not mentioned anywhere in the documentation on either instances or environment.

For people moving from Docker to Singularity, singularity instance start can be seen as a docker run equivalent. Variables set at docker run are persisted to later docker exec calls on the same container, so it's a reasonable (if incorrect) assumption that the same would be true for singularity instances. Having the actual behavior directly stated in the docs would be really helpful.

[pedroalvesbatista]

@DrDaveD I guess that this issue can be worked as it concerns the docs.

I'll take a deep look and investigate if there is some non-descriptive enough about singularity instances.