Flattening a Docker Image to a Single Layer
- Set up a new project directory to create a basic image:
cd ~/ mkdir alpine-hello cd alpine-hello vi Dockerfile
- Create a Dockerfile that will result in a multi-layered image:
FROM alpine:3.9.3 RUN echo "Hello, World!" > message.txt CMD cat message.txt - Build the image and check how many layers it has:
docker build -t nonflat . docker image history nonflat
- Run a container from the image and export its file system to an archive:
docker run -d --name flat_container nonflat docker export flat_container > flat.tar
- Import the archive to a new image and check how many layers the new image has:
cat flat.tar | docker import - flat:latest docker image history flat
