How to include files outside of Docker's build

Question

How can I include files from outside of Docker's build context using the "ADD" command in the Docker file?

From the Docker documentation:

The path must be inside the context of the build; you cannot ADD ../something/something, because the first step of a docker build is to send the context directory (and subdirectories) to the docker daemon.

I do not want to restructure my whole project just to accommodate Docker in this matter. I want to keep all my Docker files in the same sub-directory.

Also, it appears Docker does not yet (and may not ever) support symlinks: Dockerfile ADD command does not follow symlinks on host #1676.

The only other thing I can think of is to include a pre-build step to copy the files into the Docker build context (and configure my version control to ignore those files). Is there a better workaround for than that?

Answer 1

I believe the simpler workaround would be to change the 'context' itself.

So, for example, instead of giving:

docker build -t hello-demo-app .

which sets the current directory as the context, let's say you wanted the parent directory as the context, just use:

docker build -t hello-demo-app ..

Answer 2

I had this same issue with a project and some data files that I wasn't able to move inside the repo context for HIPPA reasons. I ended up using 2 Dockerfiles. One builds the main application without the stuff I needed outside the container and publishes that to internal repo. Then a second dockerfile pulls that image and adds the data and creates a new image which is then deployed and never stored anywhere. Not ideal, but it worked for my purposes of keeping sensitive information out of the repo.