How to make a build arg mandatory during Docker build?

Question

Is there any way to make a build argument mandatory during docker build? The expected behaviour would be for the build to fail if the argument is missing.

Answer 1

You could do something like this...

 FROM ubuntu:14.04
 ONBUILD ARG MY_VARIABLE
 ONBUILD RUN if [ -z "$MY_VARIABLE" ]; then echo "NOT SET - ERROR"; exit 1; else : ; fi

Then docker build -t my_variable_base .

Then build your images based on this...

FROM my_variable_base
...

It's not super clean, but at least it abstracts the 'bleh' stuff away to the base image.