How to flatten a Docker image?

Question

I made a Docker container which is fairly large. When I commit the container to create an image, the image is about 7.8 GB big. But when I export the container (not save the image!) to a tarball and re-import it, the image is only 3 GB big. Of course the history is lost, but this OK for me, since the image is "done" in my opinion and ready for deployment.

How can I flatten an image/container without exporting it to the disk and importing it again? And: Is it a wise idea to do that or am I missing some important point?

question from:https://stackoverflow.com/questions/22713551/how-to-flatten-a-docker-image

Answer 1

Up from Docker 1.13, you can use the --squash flag.

---

Before version 1.13:

To my knowledge, you cannot using the Docker api. docker export and docker import are designed for this scenario, as you yourself already mention.

If you don't want to save to disk, you could probably pipe the outputstream of export into the input stream of import. I have not tested this, but try

docker export red_panda | docker import - exampleimagelocal:new