How to include files outside of Docker's build context?

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:

T

Answer 1

You can also create a tarball of what the image needs first and use that as your context.

https://docs.docker.com/engine/reference/commandline/build/#/tarball-contexts

Answer 2

As is described in this GitHub issue the build actually happens in /tmp/docker-12345, so a relative path like ../relative-add/some-file is relative to /tmp/docker-12345. It would thus search for /tmp/relative-add/some-file, which is also shown in the error message.*

It is not allowed to include files from outside the build directory, so this results in the "Forbidden path" message."

Answer 3

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 4

The best way to work around this is to specify the Dockerfile independently of the build context, using -f.

For instance, this command will give the ADD command access to anything in your current directory.

docker build -f docker-files/Dockerfile .

Update: Docker now allows having the Dockerfile outside the build context (fixed in 18.03.0-ce, https://github.com/docker/cli/pull/886). So you can also do something like

docker build -f ../Dockerfile .

Answer 5

On Linux you can mount other directories instead of symlinking them

mount --bind olddir newdir

See https://superuser.com/questions/842642 for more details.

I don't know if something similar is available for other OSes. I also tried using Samba to share a folder and remount it into the Docker context which worked as well.

Answer 6

An easy workaround might be to simply mount the volume (using the -v or --mount flag) to the container when you run it and access the files that way.

example:

docker run -v /path/to/file/on/host:/desired/path/to/file/in/container/ image_name

for more see: https://docs.docker.com/storage/volumes/