How to get access to Dockerfile of a docker image?

How to find the Dockerfile for this image?

There is no Dockerfile for that image.

The gcr.io/distroless/base image is built from this repository. If you read through the README, you'll find:

How do I use distroless images?

These images are built using bazel, but they can also be used through other Docker image build tooling.

Bazel is a build tool that can be used to create Docker images.

What does distroless image mean?

That means the image isn't based on any particular distribution; it includes only a minimal set of files so that the final image contains only what is strictly necessary to run your application:

• ca-certificates
• A /etc/passwd entry for a root user
• A /tmp directory
• tzdata
• glibc
• libssl
• openssl