How to generate a Dockerfile from an image?

Question

Is it possible to generate a Dockerfile from an image? I want to know for two reasons:

1. I can download images from the repository but would like to see the recipe that generated them.

2. I like the idea of saving snapshots, but once I am done it would be nice to have a structured format to review what was done.

Answer 1

I somehow absolutely missed the actual command in the accepted answer, so here it is again, bit more visible in its own paragraph, to see how many people are like me

$ docker history --no-trunc <IMAGE_ID>

Answer 2

It is not possible at this point (unless the author of the image explicitly included the Dockerfile).

However, it is definitely something useful! There are two things that will help to obtain this feature.

1. Trusted builds (detailed in this docker-dev discussion
2. More detailed metadata in the successive images produced by the build process. In the long run, the metadata should indicate which build command produced the image, which means that it will be possible to reconstruct the Dockerfile from a sequence of images.