References: https://docs.docker.com/engine/reference/builder/#arg
Within a dockerfile the ARG option is the only method to paramertize the FROM command, which led to this testing.
The ARG parameter is used via the --build-arg arg=value syntax on the docker build command line.
With a dockerfile like:
ARG image
FROM ${image}
EXPOSE 80
The following command line:
$ docker build --build-arg image=alpine -t img .
Will result in a img image derived from alpine:latest.
ARG statements can also be used to parameterize other statements in the dockerfile. To use an ARG with other statements it must be declared after the FROM statement.
With a dockerfile like:
ARG image
FROM ${image}
EXPOSE 80
ARG tag
COPY ${tag}.txt \.
The following command line:
$ docker build --build-arg tag=foo --build-arg image=alpine -t img .
Will result in a img image derived from alpine:latest, with a foo.txt file copied into the root of the image.