dockerfile - Many <none> images created after build a docker image

Question

FROM scratch
MAINTAINER Aario <AarioAi@gmail.com>
ENV SHARED_GROUP docker

I build a docker image with above dockerfile. After runing docker build -t "aario/centos" . It creates this image aario/centos and the <none> image:

Is it ok? And how to solve it?

When I run docker rmi 2f??????? to remove the aario/centeros image. The <none> image will be removed on the same time.

Answer 1

Docker image is composed of layers:

docker history aario/centos

Each row you see using command above is a separate layer. Also, with time, a number of "orphaned" layers will fill up your disk space. You can safely remove them with:

docker image prune