How to test dockerignore file?

Question

After reading the .dockerignore documentation, I'm wondering if there is a way to test it?

Examples

**/node_modules/ 

How do I check my dockerfile ignore the correct files and directories?

Answer 1

To expand on VonC's suggestion, here's a sample build command you can use to create an image with the current folder's build context:

docker image build --no-cache -t build-context -f - . <<EOF FROM busybox WORKDIR /build-context COPY . . CMD find . EOF 

Once created, run the container and inspect the contents of the /build-context directory which includes everything not excluded by the .dockerignore file:

# run the default find command docker container run --rm build-context  # or inspect it from a shell using docker container run --rm -it build-context /bin/sh 

You can then cleanup with:

docker image rm build-context 

Answer 2

To get a detailed analysis of the build context you could use pwaller/docker-show-context.

$ go get -v -u github.com/pwaller/docker-show-context $ cd ~/path/to/project/using/docker $ docker-show-context 

It outputs statistics about the build such as file sizes and upload times.