Install a RPM from build context without copying it first

Question

During dockerbuild, I'd like to install a (rather big) RPM from build context/host without copying it first into the image in order to keep my image small. Ideally, there would be a way to read a file directly from build context.

What are my options (beside using a HTTP server on the host)? What are the best practices for this use-case?

Answer 1

Using buildkit, you can mount from the build context with type=bind to access files without including them in your resulting image.

# syntax=docker/dockerfile:1.3
FROM base
RUN --mount=type=bind,source=./rpms/,target=/rpms/ \
    yum install /rpms/package.rpm

See the buildkit docs for more details.