docker: extracting a layer from a image

Question

Let\'s take the whalesay images as an example. docker history shows the following:

IMAGE               CREATED             CREATED BY                    


        

Answer 1

While not capable of extracting a specific layer, the docker-save-last-layer command line utility is made to extract the last layer only. Combined with docker build --squash you can avoid exporting the base layers. This may help to accomplish your goals.

It works by using a patched version of the docker daemon inside a docker image that can access the images on your host machine. So it doesn't require doing a full docker save before using it. This makes it performant for large base images.

Typical usage is simple and looks like:

pip install d-save-last

docker build --t myimage --squash .
d-save-last myimage -o ./myimage.tar