docker - Disable cache for specific RUN commands

Question

I have a few RUN commands in my Dockerfile that I would like to run with -no-cache each time I build a Docker image.

I understand the docker build --no-cache will disable caching for the entire Dockerfile.

Is it possible to disable cache for a specific RUN command?

Answer 1

There's always an option to insert some meaningless and cheap-to-run command before the region you want to disable cache for.

As proposed in this issue comment, one can add a build argument block (name can be arbitrary):

ARG CACHEBUST=1 

before such region, and modify its value each run by adding --build-arg CACHEBUST=$(date +%s) as a docker build argument (value can also be arbitrary, here it is current datetime, to ensure its uniqueness across runs).

This will, of course, disable cache for all following blocks too, as hash sum of the intermediate image will be different, which makes truly selective cache disabling a non-trivial problem, taking into account how docker currently works.