Why are two separate images created in Docker?

Question

linux

I have created a Dockerfile, building an image using a Dockerfile.

[email protected]:/var/lib/docker/Source# sudo docker build -t obraz .

As a result, on command: docker imagesI get two separate images.

But if you get an image from the Docker hub ( docker pull obraz ), then docker images
only one is displayed on command.

Dockerfile:

FROM   ubuntu:16.04
ENV    DEBIAN_FRONTEND noninteractive
RUN    apt-get --yes update; apt-get --yes upgrade; apt-get --yes install software-properties-common
RUN    sudo apt-add-repository --yes ppa:webupd8team/java; apt-get --yes update
RUN    echo debconf shared/accepted-oracle-license-v1-1 select true | debconf-set-selections  && \
       echo debconf shared/accepted-oracle-license-v1-1 seen true | debconf-set-selections  && \
       apt-get --yes install curl oracle-java8-installer ; apt-get clean

RUN    chmod +x /start
EXPOSE 80
VOLUME ["/data"]
CMD    ["/start"]

Answer 1

In the first case, you collect the image on your computer. The first line in your dockerfile says that the image is based on the ubuntu:16.04 image, so it is first downloaded and then used to build the image. In the second case, you do not build the image on your computer, but download the finished one from the dockerhub.