Azure-devops-docs: DEBIAN_FRONTEND=noninteractive ARG instead of ENV?

[zoekdestep]

Regarding this doc: https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/docker?view=azure-devops

Recently have been reading some discussions on ENV DEBIAN_FRONTEND=noninteractive, as in https://github.com/moby/moby/issues/4032 and https://github.com/grafana/grafana/pull/20196/commits/2b7487579b5f79a74d68e5cbd6f.

In:
FROM ubuntu:16.04
ENV DEBIAN_FRONTEND=noninteractive
RUN echo "APT::Get::Assume-Yes \"true\";" > /etc/apt/apt.conf.d/90assumeyes

Shouldn't ENV be replaced by ARG? As ENV makes the variable persist in the final image, while ARG makes sure it's only set during build?

[steved0x]

@zoekdestep I will find out and if so we will update the docs. Thank you for your feedback.

[vtbassmatt]

The idea was that some pipelines run apt or apt-get as part of their normal flow. By setting this variable and having it persist into the final image, that works more smoothly.